Dust Free So Far and Healthy Snowpack
Greetings From Silverton,
Despite a dry and lackadaisical start to winter, persistent snowcover in Senator Beck occurred on November 21, we have seen a major turn-around with a steady stream of productive storms. We have received eight winter storms so far (Storm #8 Report will follow shortly) that in and of themselves have totaled ~10.0" of water. Snow depth at Swamp Angel is at 4.5’ and the wind effected Senator Beck site is lingering around 1.5’.
Greetings from Silverton,
Well good riddance to WY2018. After Colorado’s warmest and 3rd driest (driest for northwestern and southwestern Colorado) water year on record, it is a relief to begin a new water year accompanied by cooler than normal air temperatures and a nice dose of precipitation in western, eastern Colorado, and some mountain areas. In the past three weeks we received tropical moisture from hurricane Rosa and Sergio and in addition a productive system out of the north. In our Senator Beck Study Basin located at Red Mt Pass in the San Juan Mountains, so far this water year we have received 4.6” precipitation and at our higher monitoring site (12,200’) we have 15” of snow accumulation. The precipitation has slowly started showing itself in our stream gauge. Hard to imagine streams being in a much worse state, a few weeks ago all stream channels in Senator Beck were dry (and the Animas River at its lowest flows in 107 year record), with only a trickle of water coming to the surface a few hundred feet upstream of our gauge near the outlet of the watershed. After such a devastating WY2018 we have a long way to go in making up such a large precipitation deficit. At least the long-term forecast going into WY2019 is calling for a pattern shift from what we experienced last year. There is a 70-75% chance of El Nino conditions this winter which bodes well for bringing increased precipitation to the southwest.
Storm Reports: Now that the higher elevations in Senator Beck will likely hold onto the snow accumulated over the last few weeks we will begin issuing our winter storm reports. If you are not familiar, we issue storm reports following a winter storm in the San Juan Mountains. Sometimes the reports are just a few sentences and other times we do a detailed analysis on something interesting that happened or is in the forecast. To be added to our email list and be notified when we have posted a storm report to our website please contact Jeff Derry (jderry@snowstudies.org). Reports can be viewed here: https://snowstudies.org/winter-storm-data/
CODOS: In our Colorado Dust-on-Snow Department we are looking forward to serving the snow and water community for another winter season with dust-on-snow observations and assessments as to the influence of dust on snowmelt timing and rates around Colorado. If you have a new colleague in your office that would benefit from our CODOS updates please forward along our contact information to add them to our update notification email list. As a reminder, our updates are posted to our website along with all kinds of other snowpack and streamflow observations and analysis: http://www.codos.org/#codos
Snow School for Water Professionals: Once again we are offering Snow School for Water Professionals this year from February 20 - 22, 21018. This combination classroom and field course will begin on Wednesday morning at our office in Silverton and end on Friday afternoon. This class is perfect for anyone wanting to learn more about the role of snow and our mountain systems as it pertains to water resources. Attached is a flyer, please post in your workplace and please do not hesitate to contact me with questions.
Below are a Few Links to Stay Informed about Snow, Water, and our Mountain Ecosystems:
Colorado Climate Center: http://climate.colostate.edu/~drought/
H2O Radio: http://h2oradio.org/CurrentStory.html
Water Information Program: https://waterinfo.org/
Water Education Colorado: https://www.watereducationcolorado.org/
Rocky Mt Climate Organization: http://www.rockymountainclimate.org/
Hutchins Water Center, Mesa State: https://www.coloradomesa.edu/water-center/index.html
More soon.
After a worrisome October and November when Colorado received very little precipitation and experienced very warm temperatures, winter finally kicked into action and Colorado started receiving abundant snowfall, building the snowpack rapidly during the months of December, January, and into February. One of the big stories this winter season is the atmospheric rivers that fueled these productive storms, which were record breaking in some locations. On the other end of the spectrum, one of the other big stories this winter is the observed warmest March on record. The effects of this hot month (preceded by a very warm February) was a rapid warming of the snowpack and snowmelt at lower elevations and valleys, resulting in most stream gauges observed a 2-3 week bump in stream flow in mid-March thru the first part of April. However, Colorado recovered from the hot/dry spell with a long stretch of regular precipitation beginning around March 23 – April 4. A dry spell was again repeated April 5-19. And, starting the latter part of April regular precipitation (however sparse) was observed steadily but intermittently until June 1.
At the Center for Snow and Avalanche Studies’ (CSAS) Senator Beck Basin Study Area (SBB) at Red Mountain Pass, the primary Colorado Dust-on-Snow Program (CODOS) monitoring site, WY2017 produced a total of four separate dust-on-snow events, on the light side of a typical dust loading season based on observations going back to WY2005. Dust season began relatively late in the season. With the abundant moisture in the dust source area, the Southern Colorado Plateau, dust mobilization was kept in check until March when soils started drying out. Dust-on-snow events March 5, 23, 31 and on April 9 were documented. Surprisingly no dust events were observed the rest of April and May, although a couple haze events were noted. On June 12 a big dust storm in the desert southwest was observed with the USGS dust cameras, additional dust on any remaining snow in the Colorado Mountains was not observed at lower elevations, but it is possible some higher elevation snow cover could have received additional dust from this event. Of the four documented dust events, two of these events were pretty heavy in their severity. The end result, even though total mass loading of dust was light, with the location of the dust in the snowpack (i.e. upper portion) and its consequential role in snowmelt, we classified dust severity as “Average”, albeit the lighter side of average at SBB. Northern and some Central CODOS sample sites in Colorado were classified as “Minimum” dust severity. The transition from “Average” to “Minimum” severity took place in Central Colorado, thus some Central and all Southern CODOS sites were classified as “Average”.
Greetings from Silverton,
In Senator Beck Basin (SBB), Senator Beck Study Plot (12,200') held onto snow only a week longer than Swamp Angel (11,100'). Not to say snow is completely gone at higher elevations but it has been going fast. Current snow covered area in the Uncompahgre is around 22% and is 14-28% in the other Southern Colorado, high elevation basins. Of course some of the Central and Northern basins have a bit more snow cover but these basins are also seeing rapid ablation. It has been the worst combination of factors this spring; a shallow snowpack, an average to high-end of average dust-on-snow conditions around the state (which has been solidly exposed since May 2), a complete lack of significant spring storms and in it's stead warm/sunny conditions (at SBB we went 16 days in May without recording any precipitation), all has combined to melt the snow early and fast. With the warm air temperatures evaporative demand is extremely high as well, quickly taking what moisture exists from the soils and plants. The area around "Swamp" Angel is currently very dry with little of the usual wet soils. Typically, it is a very interesting time of the season when snow melts out at SNOTEL stations, leaving the majority of snow at higher elevations above ground-based monitoring networks - except for SBB. And typically when SBSP melts out we see a second surge in the snowmelt hydrograph at Senator Beck stream gauge. But this year according to our observations higher elevations have acquired an amount of snow relative to lower elevations and does not appear we will see much of a second bump.
Warmer weather is expected to continue over the next couple weeks and in the mountains there are chances of afternoon thunderstorms, but that is about it. Please see SWE, streamflow, and SBB plots below.
More from Silverton soon.
Just to make this plot even more busy, I added Snow Covered Area (%) in the Uncompahgre Basin since this is the watershed that Senator Beck is located, and to show the relationship with Uncompahgre River flows. Currently, SCA is around 22% based on the SNODAS Decision Support System. Snow was all gone at SASP by May 16, which is why we see the dive in albedo at that time. Streamflow is well past its peak in Southern Basins and for a number of Central Basins.
Snow under the depth sensor at Senator Beck Study Plot reported 0" as of 5 pm on May 23. Senator Beck stream gauge at 11,000' saw its peak discharge on May 17, whereas most gauges in Southern Colorado, being located lower in their basins and thus integrating all the runoff in the watershed, saw peak the prededing week.
We finally recorded precipitation at SBB over the last four days, but only totaling 8 mm (0.3"). Prior to that we did not see precipitation since May 2.
Ablation rates for a few select SNOTEL stations. Ablation is faster than normal around Colorado. Wolf Creek melted out over 5 weeks early. Rabbit Ears is on track to melt out about 7-10 days early. Red Mt SNOTEL melted about 2 weeks early. And Berthoud is on track see snow all gone about a week earlier than normal.
Greetings from Silverton,
On May 14 and 15 we visited CODOS sites at Hoosier Pass, Loveland Pass, Berthoud Pass, Willow Creek Pass, and Rabbit Ears Pass to assess current conditions. We observed nothing unexpected, events have been transpiring as we have reported, informed by our visits in March, April, and unfolding weather conditions. Mainly, dust conditions have been solidly in the "Average" category statewide essentially since D5 occurred on April 12, and in the Southern Basins since late March/early April when D3/D4 occurred. Within this "Average" categorization, conditions are largely consistent in severity at the Front Range and Northern CODOS sites, and also as observed at high elevations. Higher elevations show pronounced dust coverage mostly on lee aspects and areas where the wind would be expected to subside and allow the dust to be deposited.
Spring weather occurring after April 1 added a nice boost to Central and Northern Colorado Basins resulting in peak SWE occurring well into April, but the Gunnison and Southern Basins largely missed out on these events and saw peak SWE occurring very near April 1. The Central and Northern Basins benefited not only from the additional precipitation but accompanying short-term albedo resets. Nonetheless the below average snowpack, dust conditions, and lack of notable spring storms mean Northern and Central Basins are on track to see SNOTEL melt out 2 - 3 weeks early than usual.
On May 15 we also made our usual observations at Swamp Angel Study Plot. The snow depth sensor reports no snow as of May 16 at 1 pm. As of May 14, snow profiles still show about 15" snow depth and 5.5" of SWE. It has been an amazing, massive melt period in the San Juans since our last storm occurring May 1 -2 (we have not received precipitation at Senator Beck since May 2). From May 8 - May 14, we lost 7.5" of SWE, that is over 1" SWE a day. SNOTEL stations in the Animas/San Juan/Dolores/San Miguel are within a day or two of reporting snow-all-gone, at least 21 days earlier than the median date. In the Rio Grande, Wolf Creek SNOTEL in a 10 day period (May 3 - May 12) lost 12.3" of SWE, that is 1.23" SWE/day. SNOTEL stations in the Rio Grande are showing snow-all-gone as of a few days ago, 41 days earlier than the median date.
Streamflows have kept up a steep rising limb across the state, most notably in the Southern Basins, in response to the rapid snowmelt. This has tapered off in the last couple days with cloud cover and a depleting snowpack in general is manifested. There is still snow in the San Juans to be melted (please see pictures below), the location of which is creeping up in elevation plus some northerly aspects. I plan to report more on this in a future Update (it was already introduced in the March 9 Update), but generally within a few days, when snow is gone from SASP is when 50% of cumulative streamflow from March 1 - June 30 has passed through the Senator Beck stream gauge. And we are very near that point when snow is considered gone at SASP.
Please see plots, pictures, and more comments/observations below.
Swamp Angel Study Plot: May 15, 2018
Albedo at Swamp Angel has taken a nose dive with snow cover depleting rapidly. Senator Beck Study Plot has retained a little more snow than Swampy since May 2, but given its elevation (12,200') is melting quickly as well. The forecast is sunny and above freezing temperatures until the weekend when chances of precipitation come into the picture.
At 1 pm on May 16 snow depth under the sensor at Swamp Angel reported 0. Senator Beck Study Plot shows 12" of snow remaining. Streamflow took a short timeout from its upward trajectory in response to a couple days of improved albedo and cooler weather. We have not seen precipitation since May 2. Have we seen peak discharge at Senator Beck? Good question. I would not be surprised to see a higher peak given the clear and warm forecast the next couple days, and considering the amount of snow still remaining in the Basin. Please see pictures below of Senator Beck Basin. If it does not happen in the next few days, the inclement weather predicted over the weekend will likely slow down melt rates and resultant streamflow.
Snow cover is nearly gone at SASP. Where the snow profiles are conducted snow depth is currently around ~9". From May 8 - May 14, we lost 7.5" of SWE, over 1" SWE a day.
May 14 at Swamp Angel. Snow sensor reported 0" of snow depth on May 16 at 1 pm. Although, there is still some snow yet to be melted.
Photo showing Swamp Angel and northerly aspects that still have snow.
Shallow snow pit shows snow remaining at Swamp Angel. All layers merged samples were collected on this day (May 14).
Clean snow exposed to highlight dirty snow.
Senator Beck stream gauge. Stream still has snow/ice covering sections of stream that formed in early winter.
Stream, Snow, and Forecast Plots
We are entering an active weather pattern but beneficiaries will be more eastern and northern areas of Colorado.
Hoosier Pass: May 14, 2018
Snow Profile at Hoosier Pass, May 14, 2018. SWE is 10.7". All dust layers at surface.
Hoosier Pass. Contrast between dirty snow surface and clean snow underneath.
Hoosier Pass. Where there is snow at higher elevations, dust is easily visible in depositional areas.
Grizzly Peak (Loveland Pass): May 14, 2018
Snow profile at Grizzly Peak. 10.6" of SWE. As elsewhere, all dust at surface.
Looking up valley towards Loveland Pass from sample site.
View towards A-Basin ski area from top of Loveland Pass.
View towards the northwest from Loveland Pass.
Berthoud Pass
Berthoud Pass snow profile, May 14, 2018. SWE is 13.9".
Snow profile with SNOTEL in background.
Berthoud Pass.
Willow Creek Pass
Willow Creek on May 14, 2018. Snow all gone at sample site. Forested areas retain some intermintent snow.
Picture of high country from Willow Creek Pass sample area.
Looking south from Willow sample area. Intermittent snowcover in treed areas.
Rabbit Ears Pass: May 15, 2018
Rabbit Ears snow profile. SWE is 19.4".
View of snow pit and surrounding landscape at Rabbit Ears Pass.
Clean snow block in foreground to show contrast with dirty snow surface at Rabbit Ears.
Greetings from Silverton,
The Senator Beck Basin (SBB) received its eighth dust event of the season yesterday afternoon (May 11) and into the evening. No surprise, the morning of May 11 Phil (CSAS employee) was driving through the four corners region on the way to Prescott and said it was white knuckle driving with the high winds and dust. Then in the afternoon the San Juans started seeing the winds and hazy skies. Dust cameras are showing dusty skies this morning so more dust is possible today (May 12). This event is falling on an already dusty snow surface so it will be difficult, if not impossible, to assess its severity. We will take mass loading samples and deduce loading of this event by subtracting out other sample weights from other individual dust events. But the damage is already done. The existing cumulative dust layers at the snow surface along with the relentless sunny/warm weather is melting the snow quickly. In the last 7.5 days at Swamp Angel we lost 17.7" of snow depth. Red Mountain SNOTEL lost 5" of SWE in the same time-frame, and currently shows 8.4" SWE remaining. Wolf Creek lost 8.2" SWE and currently shows 3.8" remaining. We will report on our findings for Northern and Front Range CODOS sites at mid-week.
More from Silverton soon.
Photo from Abajo dust camera the morning of May 12. At the time of this writing more dust could be coming to the Colorado mountains.
Winds have been straight out of the SSW for the duration of dust event #8
Greetings from Silverton,
The CODOS team visited Central and Southern sample locations May 9-10. Snow was completely melted out at Wolf Creek, Spring Creek (which was already nearly fully melted out on April 16), and Park Cone sites. Wolf Creek Pass has some snow cover on north facing slopes above 11,000 feet but is otherwise melted out. At Grand Mesa there is absolutely no snow below 10,000', which has been the case for some time, with about 90% of snow coverage on the Mesa itself. At the Grand Mesa CODOS site we observed only 10" of snow depth and 3.6" of SWE, with dust conditions on the upper end of average (pretty dirty). Dust conditions are classified as "Average" across the state, but there is a little variation in dust intensity within that designation. The San Juans and Grand Mesa are on the high end of average, while Northern Colorado and Front Range locations sit more in the middle part of average.
In a nutshell, the snow surface is quite dirty. The snow is melting fast after the rain and wet snow event on May 1-2, which deteriorated quickly giving rise to all dust layers at the surface of the snow. In response streamflows have been spiking. Seasonal peaks are expected at many locations with this melting surge. Given the weather forecast and dust conditions, projection plots show SNOTEL stations in the Rio Grande are on track to be melted out over a month earlier than normal. The San Juan/Dolores/San Miguel/Animas Basin will be about a month early. The Gunnison is on track to melt out about 3-4 weeks earlier than the median date.
The weather forecast over the weekend has changed from a good chance of snow/rain in the San Juans to sunny and windy. Added to that in the four corners region there is a wind advisory with expected areas of blowing dust. So instead of a chance of rain/snow we can expect it to be sunny/windy with a chance of more dust deposition on an already dirty snow surface - accelerating snowmelt and sublimation rates even further. As you go towards Northern Colorado chances of precipitation increase, mostly in the form of rain except at higher elevations. It does not appear the majority of the mountain regions are going to receive any reprieve from current conditions in the near future. The remainder of May is forecast to be warmer and drier than average across the Southwest.
Please see pictures, captions, and plots below.
We will assess Northern Colorado CODOS sites in a couple days and report our findings ASAP.
More soon.
Wolf Creek Pass. Picture captures snow-all-gone conditions on southerly aspects and snow cover still remaining at higher elevations and northerly aspects.
Wolf Creek CODOS sample site essentially completely melted out. This site has a SSW aspect, across the highway the Wolf Creek SNOTEL reports 7.3" of SWE remaining.
Wolf Creek Pass, looking at southerly aspects of the landscape showing snow-all-gone.
Spring Creek Pass was nearly completely melted out on our last CODOS visit on April 16. Now there is no snow to be found anywhere in the area.
Looking in a northerly direction at Spring Creek Pass.
Looking toward Lake City from Slumgullion Pass. From where this photo was taken, dust was easily seen on the 14,000' peaks (on right side of picture).
Looking out over Taylor Park Reservoir. Mid/Lower elevations are melted out but more snow exists in the high country than what is seen in the San Juans.
Grand Mesa sample site. 10" of snow depth and 3.6" SWE remains. All dust layers are at the surface.
Approaching the Grand Mesa dust sample site.
Look out over Grand Mesa.
Greetings from Silverton,
The 11” of snow accumulation received May 1-2 has now melted down to where dust events 2-7 once again are at the surface of the snowpack at Swamp Angel, Senator Beck and majority of the surrounding landscape. With the warm and sunny weather since the 1st of May storm, SNOTEL data across the state are now beginning to report snow depths and water equivalent at or below values prior to the storm, indicating dust is fully exposed at all monitoring points. The combined dust events are bordering between "average" and "maximum" dust severity. We have had only 2 previous years that achieved the status of "maximum" dust severity in our period of record. As of right now we will classify severity conditions as "high end of average", but his may change with further data analysis. Please see plots and captions below discussing this past week in more detail.
Average and minimum air temperatures are staying above freezing and the forecast is for this to continue. Over the next 7 days Southwest Colorado is expected to receive around only 0.10"-0.14" precipitation in the mountains, as you move east and north precipitation amounts are expected to increase with the mountain regions expected to see anywhere from 0.23"-0.65". Besides possibly seeing a day of cloud cover (tapping the brakes on snowmelt), it is supposed to remain sunny. With the season's dust now completely at the surface, above freezing minimum temperatures, negligible precipitation and sunny days in the forecast, the faucet is turned on in terms of melting what little snow exists in Central and Southern Colorado. Northern Basins which are faring a little bit better - Yampa/White, South Platte, Colorado Mainstem - are projected to hold onto snow into June, but dust exposure might have something to say about that unless wetter spring conditions prevail in these Basins than are expected in the Southern part of Colorado.
Please see plots and below.
More soon.
This morning, May 8, at Swamp Angel Study Plot. All layers are now merged.
This morning, May 8, going up towards Senator Beck Study Plot. The dust severity can be seen by comparing ski tracks and sloughed areas.
The May 1-2 storm brought 0.9" of water and 11" of snow accumulation plus initiated a major albedo reset. But, given the wet snow that was deposited, sunny days and above freezing air temperatures at night. snowpack albedo decayed rapidly as it gradually gave rise to dust layers 2-7, resulting in a spike in streamflow. Currently, the forecast is for continued above freezing minimum temperatures and sunny conditions. With D2-D7 now at the surface, we are going to continue to see rapid snowmelt. Over the weekend we may see a chance of precipitation, we are not expecting much (forecast is calling for 0.14" over the next 7 days), but it might provide cloud cover for a day or two, possibly slowing down melt only temporarily.
Above plot shows snow depth, albedo, and streamflow at our SBB gauge. Interestingly, on May 1 median snow depth at SASP and SBSP cross over, where the snowpack begins rapid ablation at SASP and the higher elevation SBSP holds onto the snow longer into the summer and creates the second peak seen in the median streamflow data. This year, we are about a month earlier than normal. SBSP will likely hold onto the snow longer than SASP but not by much.
Greetings from Silverton,
Since our last Update on April 25 dust layers have fully emerged at our Senator Beck Study Basin and all but the most unique locations (i.e. high elevation north facing nooks) throughout the San Juans. At Swamp Angel full emergence of D6-D7 occurred on April 27. There was a small separation of D6-D7 from D3-D5 as of April 29, but observations May 1 show all dust layers are now combined at the surface. Now too, D2 – which has been lurking 30” above the ground - is now only 4” below the surface. D3-D7 already make for a very dirty layer and D2 is no slouch either, once these layers merge the remaining 30” of snow at Swamp Angel, and by extension the Northern San Juan Mts, will see the worst dust conditions of the season (unless we receive more dust events) and rapid melt under sunny conditions. Judging by SWE ablation at SNOTEL sites across Colorado dust, and its severity as described in our April CODOS tour Update, is at the surface at all locations as well.
The steep rise in streamflow in response to the sunny/warm conditions and surfacing/exposed dust around much of Colorado over the last two weeks is slacking off a bit with the arrival of a series of Pacific Storms moving across Colorado today through Thursday. The forecast is calling for widespread precipitation across Colorado, hopefully it will fall mostly in the form of snow to cover existing dust and add to our snowpack reservoir. Judging by the forecast and what we have received so far at SASP (0.5" precipitation with 6" of snow accumulation), dust will stay covered for a number of days following the passing of this system.
No D8 Observed: We had high southwest winds accompanied with dust warnings in the source region on April 29-30. The sky appeared clear in the San Juan’s throughout the entire duration of the event but there were observations of dust in the air in some of the western valleys and there appeared to be some brown haze over some of Colorado’s central mountains. Prior to the wind event we cleared the snow down to a clean surface at SASP and did not observe any new dust following the event. If any new dust was deposited elsewhere in Colorado it is very likely indistinguishable from existing dust already at the surface.
May CODOS Tour: With the drastic differences in snowpack between Northern and Southern Colorado the CODOS team is going to split the timing of our visits. We will visit the San Juan, Grand Mesa, and Park Cone sites around May 7-9 hopefully to document the reemergence of dust to the surface following this current storm – and its impact on the remaining snowpack. We will visit the Northern and Front Range sites a few days later to assess dust impacts on this closer to normal snowpack regime.
Please see plots and below.
Albedo continued to degrade as dust merged to the surface this past week. Cloud cover and cooler temperatures, followed by fresh snow on the dust resulted in decreasing streamflows, Streamflow may increase with possible rain falling in watersheds. Overall, snow received in the Colorado high country will provide an albedo reset with a duration dependant on the amount of snow received and sunny/warm conditoins following this current storm system.
Average albedo from SASP and SBSP with snow depth and streamflow. We lost a good amount of snow depth and SWE this past week. Streamflow at our gauge responded with a sharp spike, as did many throughout Colorado.
Pictures taken of dust-on-snow rarely accurately show the severity of the dust. The clean snow in this picture is seen in the snow blocks.
Greetings from Silverton,
Red Mt. Pass: The snow accumulation received April 20-21, after dust event #7 was deposited on April 19, is nearly melted down to dust layers D3/D4/D5/D6/D7 at Swamp Angel Study Plot. These combined dust events make for a very dirty layer that will enhance snowmelt for the foreseeable future, likely until the snowpack has completely ablated. Currently, D3-D7 is 2" below a pretty clean snow surface at SASP but emerging rapidly. It is surprising the dust has not emerged sooner based on how very wet the snow is near the surface in the afternoons these last few days. But temperatures in the evenings have been well below freezing, and along with radiative cooling, refreezing the top ~ 9" of the snowpack at night, hence the following mornings melt energy goes toward warming up the snow before energy goes toward melting the snow. Still, the dust is already increasing snowmelt, as solar radiation can penetrate up to 1' into the snow depending on various factors, and with this dust just under the surface it is helping the snow absorb more radiation than otherwise. Snowmelt will really be ramped up when the dust is fully exposed and the faucet turned on when nighttime temperatures stay above freezing. In the San Juans in general dust is already enhancing snowmelt where exposed on the snow surface in areas such as steep slopes, southerly and exposed aspects, and shallow areas. Where the dust is exposed it makes for a very orange/brown color on the snow. Currently, dust is exposed on roughly 60%-70% of the existing snowcover. Also where there is bare ground, and there is a lot of it, it is warming and melting the adjacent snow faster than if there was complete snow cover. Over the last few days we have seen an uptick in streamflow. This will continue possibly until our next chance of precipitation and fresh snow accumulation, where we might see a temporary albedo reset. Please see albedo, air temperature, and streamflow plots below.
This is the time of year where we show streamflow as it relates to albedo of the snow surface. Most streams in Colorado saw an uptick in flows during a mostly rain event, with some wet snow, on April 8-9. Albedo is currently declining rapidly with the emerging dust and streamflows have increased over the last couple days. Minimum nighttime air temperatures have been cold, freezing the top ~ 9" of the snowpack. Expect albedo to continue to degrade until we receive snow. Overcast conditions over the weekend and maybe next week could slow daily melt rates.
The ablation season is underway at SASP. Elevation 11,060'.
SASP on the morning of April 25. D6-D7 is 2" under the surface with D3-D5 slightly beneath. D2 is about 1' beneath D3-D5.
SWE at SBSP on April 25, elevation 12,200'.
At Senator Beck Study Plot on April 25 dust is approximately 4" below the surface but exposed in the surrounding terrain.
Rio Grande: Dust layers were merged at the surface in the Rio Grande during our CODOS tour on April 16. It was of greater severity than Swamp Angel. Judging by the amount of precipitation received over the April 19-21 storm event (Wolf Creek and Upper San Juan SNOTEL showed around 0.7" precipitation, 2" snow depth gain, and ~1" reported SWE, basically no precipitation at Lilly Pond which is now showing snow-all-gone, and 0.2" precip, 3" snow depth gain and 0.5" gain in SWE at Upper Rio Grande which is now showing snow-all-gone) any snow covering the dust was superficial, and did not slow down snow ablation any real degree. With the forecast being sunny until the minor storm system this weekend, we can expect continued snowmelt to continue likely even more so with any possible coverage of dust assuredly now exposed at the surface.
Central Colorado: Generally, more precipitation was reported from the April 19-21 storm as you move north. Observations from other snow scientists driving around Colorado yesterday (April 24) reported that dust was not exposed in the Crested Butte area. But near Park Cone SNOTEL, where dust was on the surface on April 16, station data reported 0.5" precip, 0" snow depth gain, 0" added SWE from the April 19-21 storm, so dust is very likely still exposed in that locale. Monarch Pass is showing a good blanket of pink dust. New snow accumulation of ~10" on Grand Mesa was observed from the April 19-21 storm. Mesa Lakes SNOTEL reported 1.4" of precipitation, 6" of snow depth gain and 0.8" of added SWE from the storm. Dust at Grand Mesa area is likely a few inches under the surface but emerging rapidly due to the warm weather at the CODOS sample site. Once D6/D7 is exposed it will encourage melt down to D3-D5 which was 9" below surface on April 14. Like all locations throughout the state, dust is likely already exposed on certain aspects and lower elevations. As a reminder, D5 (and possible D6 and D7) was at the surface on April 19 at Hoosier, Loveland, Berthoud, and Willow sample locations. Observers reported that dust was still covered at Berthoud Pass yesterday.
Weather Forecast: This weekend a minor storm system will take a glancing blow at the San Juans, but no significant precipitation is expected. With low energy, low moisture and an unfavorable storm track we are anticipating overcast conditions, moderate winds and minor flurries at the most.
Looking forward we are seeing another weak system move into the area early and middle of next week. This system has more favorable southwest flow, but only moderate energy and dry air. At present, this incoming system looks more like a dust event than a winter storm, but being several days out an accurate prediction is difficult. This system will likely deliver some snow to isolated parts of the state, but no one location will break any records. The long-term outlook remains hot and dry, just as it has for the majority of the winter and spring so far.
In the News: On Sunday NPR ran an article that was posted on the front page of their national website, along with that the radio portion has been getting airplay. The article discussed the problem of dust on our Colorado snowpack and highlighted the work of CSAS' Colorado Dust-on-Snow Program. You can read the article here. The radio program Here and Now ran the radio version. Rarely does any news piece mention the fact that we are a small non-profit, let alone mention who supports CSAS. So I would just like to send out a big thank you to our funders. Your long-term stable support allows the Director (me), the only full-time employee, and our two seasonal-part-time employees, to stay focused on collecting and reporting the data, because that is what really matters. Most people are surprised to hear that we are a non-profit, because these folks who understand the problem know that it is of such great importance that we must be under the wing of some sort of state or federal government. Not so. Again, a big thank you to the below entities for making what we do possible (list is not exhaustive):
Colorado Water Conservation Board
Colorado River Water Conservation District
Upper Gunnison River Water Conservancy District
Southwestern Water Conservation District
Rio Grande Water Conservation District
Tri-County Water Conservancy District
Dolores Water Conservancy District
City of Grand Junction
Denver Water (raw water)
Denver Water (climate change program)
Bureau of Reclamation
Forest Service
Rio Grande/Colorado/Gunnison/Southwestern Roundtables
Researchers in Senator Beck Study Basin
Individual Donors
And also, our thoughts go out to Steve Fearn who passed away this week. I always enjoyed watching Steve and his colleagues piece apart and work through a problem at the Southwestern Water Conservation District meetings. I was marked by his intelligence and fairness.
More soon.
U.S. Drought Monitor map for UCRB. Proposed changes for this week. From NIDIS Intermountain Drought Early Warning System.
Greetings from Silverton,
We visited Willow Creek, Berthoud Pass, and Loveland Pass CODOS sample sites yesterday to assess the presence of the hard hitting D5 event we documented on April 12. Not surprisingly, D5 was indeed a statewide dust event. It is very evident in the snow profiles and surrounding landscapes across Colorado. We updated the Update we posted on April 18 to include observations and pictures from this trip:
http://www.codos.org/codosupdates/apr182018
Like we noted in the April 18 Update, on April 17 we received dust event #6 (D6). At Swamp Angel it was a dry event that came in with very high winds. It is of light severity, we observed it on the surface of the snow on April 18, about 4" above D3-D5. Yesterday, and into the evening, we received dust event #7 (D7). During the day yesterday the cameras in the Southwest showed very hazy/dusty conditions and starting around 2 pm in the Red Mt Pass area came high winds and very suspicious looking, slightly tinted wispy clouds. D7 was primarily a wet event, arriving with rain and then wet snow falling in the San Juans, allowing it to fall on top of D6, and currently rapidly merging with D6 with this wet snow. So, D6/D7 are essentially merged at the snow surface and a couple inches above D3-D5 at Swamp Angel.
Across other parts of Southern Colorado - and possibly Central/Northern Colorado - where D6/D7 fell on already exposed dust layers, it might be difficult to discern the addition of D6/D7, depending on the severity. Where D6/D7 was deposited on clean snow that had buried D3-D5, will exacerbate the melting of snow down to these dust layers where they will all merge, drastically effecting snowmelt rates. The current weather system is expected to stick around until Saturday and deposit a few inches of snow across the Colorado high country, providing a temporary albedo reset. We will post more updates soon as conditions unfold.
Please see windrose plots for D6 and D7 below.
More Soon.
Greetings from Silverton,
Colorado Dust-on-Snow and Snowpack Conditions
The CSAS team conducted a portion of the April CODOS tour on April 11. Sites visited were the Front Range locations, Hoosier, Grizzly (Loveland Pass), Berthoud, and Willow Creek Pass. With a significant winter storm in the forecast from April 12-14, along with accompanying dust storm warnings in the source region of the desert southwest, we opted to sample remaining sites after this system – very likely to deposit dust – had passed through Colorado. It is fortunate we postponed our trip, a severe dust storm (dust event D5) occurred late afternoon on April 12, immediately followed by snow accumulation of ~9” at Swamp Angel and various amounts throughout Colorado. Due to the spatial extent and severity of D5 the dust observations we collected on April 11 at Hoosier, Grizzly, Berthoud, and Willow Creek is now rendered obsolete; therefore, we are planning on resampling these sites on April 19. Immediately following revisiting these sites we will modify this April CODOS report to include those observations.
We have been holding our breath this season in expectation of major dust events unfolding, waiting for the other shoe to drop, in a sense, on a dismal snowpack in the southern half of the state. The conditions have been ripe for it all winter with the southwest digging deeper into severe drought, making it more likely we would see large quantities of dust mobilization in the source region. This dust event (D5) comes right as the southern part of Colorado has likely reached peak SWE and the northern part of Colorado is very near peak SWE, leaving the dust on (or very near the surface) of the snowpack. Except for when it may be temporarily buried by more snow accumulation this dust will advance snowpack warming, increase melt rates, and enhance sublimation for the duration of spring.
DUST CONDITIONS: At SASP, the dust-on-snow logs so far this season unfold like this, 1) Dust event D1 was deposited on the basal layer of snow likely with a precipitation event arriving on December 21. Located at the very base of the snowpack D1 will have no influence on snowmelt. 2) D2 was deposited February 18-19 and is of moderate intensity. It is still ~20” beneath the surface at SASP and will definitely increase the hydrologic consequences once merged with successive dust events near the surface of the snowpack. 3) D3 was light and deposited March 25 as a dry event, without precipitation, on the surface of the snow. 4) D4 was another dry event deposited directly onto D3 from April 1-3. It is slightly stronger than D3, and the two layers combined are very evident on/in the snowpack at SASP. 5) D5 was a major dry event, arriving with high winds on April 12 and followed by ~9” of snow accumulation at SASP. D5 fell on top of D3/D4 which were mostly on the surface of the snow, combining these three dust layers, which are now just under the snow surface at Swamp Angel (4”) and will be a major control on snowmelt once exposed. As of this writing, D5 is on the surface of the snow at Wolf Creek, Spring Creek, and Park Cone. D5 is ~12” beneath the surface at Grand Mesa and Rabbit Ears…….Now, let’s add D6. 6) D6 occurred yesterday (April 17, from early morning to late afternoon). As the Front Range was getting clobbered with high winds and dust originating out of the San Luis Valley, the Western Slope was also getting dust – not nearly the intensity as the Front Range – from our source region of the Desert Southwest. The morning of April 18, we found D6 is predominantly a light event near Red Mt. Pass. But D6 will increase snowmelt and advance the timing of when D3-D5 will be exposed to the surface. Once this happens D3-D6 will merge into one nasty dust layer that will intensify snowmelt and sublimation rates through the remainder of the season. And……There is currently a dust storm warning in effect until the evening of April 19 in the source region. But……a closed low is also currently making it’s way to Colorado and expected to deliver precipitation starting April 19-April 21, hopefully in the form of snow and not rain as we have seen at many areas the last couple of storms so far this April (please see weather section at bottom of report). Please see notes below of our observations from the CODOS sample sites throughout the state, describing if dust is present, it’s intensity, where it is located in the snowpack.
SNOWPACK AND STREAMFLOW: Hopefully, this year will be a good lesson on how much cumulative SWE matters; meaning, precipitation added to the snowpack after the date of peak SWE to significantly make a difference in cumulative streamflow. The classic example being the “miracle May” in WY2015 where we had a very poor winter season followed by a very wet month of May that turned our water supply outlook around. So far this spring we have had a couple good storms, April 6-8 and April 12-14, that have been the cause of sharp increases in many SNOTEL projection plots throughout most of Central/Northern Colorado, and to a much lesser (if at all) degree in the Southern part of the state. As of this writing, the North Plate and Laramie basins are of average median SWE, the South Platte, Colorado and Yampa basins are of slightly below average median SWE, and the Arkansas, Gunnison, Dolores/San Miguel/Animas/San Juan and Rio Grande are well below average median SWE. As mentioned we have a couple of storms in the forecast that will deliver more snow……….and possibly dust.
As we noted in the March CODOS tour update, and as USGS gauges are attesting to, snowcover across Colorado (besides Rabbit Ears and nearby mountains) below 10,000’ is lacking. This is likely contributing to the lower stream flow we are seeing statewide. And what snowmelt runoff was present at lower elevations may have been absorbed by the dry soils.
We are posting the snow profiles collected and new photos on each CODOS site’s webpage, as well as hydrographs and SWE graphs. Below you will also find a summary table and brief discussion for each CODOS location. Using the Dust Enhanced Runoff Classification (DERC) approach, links to hydrographs of the CODOS sites from WY2006-2017 are collated and presented to help with ascertaining what this spring runoff scenario might look like. We anticipate at least one additional full circuit of our ten CODOS sites this season as well as intensive monitoring at Senator Beck Basin (SBB).
Table 1. Dust and snowpack conditions as of April 16, and updated on April 20 for Front Range sites, with current DERC categorization. This is the time of year when we try to categorize dust severity throughout Colorado into either “Minimum”, “Average”, or “Maximum”. All locations are now classified as "Average" dust severity, but within that classification there is a bit of variance. Wolf Creek, Swamp Angel, and possibly Grand Mesa are on the upper end of average, while Central and Northern Colorado are more in the middle range of average. Within that categorization, along with pictures, we try to elaborate as to the local characteristics of the dust. The intent is to assess the effects of the dust on snowmelt. The table below summarizes dust events observed during the recent CODOS tour as well as the classification of total severity of dust-on-snow at each location. Considering this information along with March 1 SWE conditions and a current estimation of spring weather conditions, previous water year hydrographs are suggested as possibly meeting similar conditions as WY2018, and what the ensuing spring runoff might look like. “Current DERC Spring Conditions” are characterizations of spring weather to date (March-April 16). If there are no previous water years in the DERC matrix to directly compare with WY2018, then these sites are noted in bold, and alternate water years are presented that may offer an idea of possible runoff scenarios that are close to current conditions. Years in parenthesis are nearest neighbor dust conditions that also may shed light on runoff scenarios. In the pdf links under each CODOS sample site are the hydrographs for viewing.
SWE CONDITIONS
BASIN SWE CONDITIONS
STREAMFLOW
PAIRED PLOTS
Senator Beck Basin – April 18
The San Juan Mountains received their sixth recoded dust event of the season on April 17th This dry event was relatively minor, although it was accompanied by extremely high wind speeds (peak of 90 mph at Putney). The new dust is variable across the landscape due to these winds and significant redistribution. Sheltered areas and depressions where blowing snow tends to deposit are exhibiting the darkest dust from this event. Ski tracks, wind pillows and creeks are good spots to observe this new event. The much darker and more worrisome D3-5 layer is about 4 inches (10cm) below the surface at Swamp Angel, and is highly visible in snowpit walls. The layer is exposed on many slopes on the surrounding landscape, especially on solar aspects and wind scoured slopes. The layer has formed a stout crust, and many loose avalanches with dusty bed surfaces have been observed running on this layer. While still on the surface, the presence of D6 may accelerate the emergence of these buried layers. However, we are hopeful that this new event will be buried shortly as a closed low-pressure system moves into the region on Thursday. It is unclear if the new snow will be accompanied by additional dust, but the National Weather Service has a dust storm warning in effect for the dust source region in Northern Arizona.
On March 1st, SNOTEL station data in the San Juan region was ranked as “Low”. We are seeing “Dry” current spring precipitation conditions, and “Average” dust conditions currently exist. USGS gauge hydrographs from four watersheds, Animas River, Dolores River, San Miguel River, and Uncompahgre River for the CODOS WY2006-2017 period of record, are collated and presented in the DERC discussion on the SBB webpage. Below are hydrographs that pertain to “Low” March 1 SWE conditions.
Uncompahgre near Ridgway (pdf)
San Miguel near Placerville (pdf)
Dolores River at Dolores (pdf)
Animas River at Durango (pdf)
Snow Profile at SASP on April 18, 2018. D6 (light) is on the surface. D3-D5 is ~4" below the surface. D2 is ~19" below the surface.
Common scene near Red Mt Pass, Bare ground showing at all elevations, scant snow in general below 10,000'. D2-D6 merged and at the surface at many locations.
Avalanches are running on dust layers D3-D5. Dust, beneath the snow but close enough to the surface still absorb solar radiation, creates a stout crust layer that provides a smooth, hard bed surface for the overlying snow to run on.
View from Swamp Angel Study Plot. Local debris is on the surface from high winds up to 90 mph were recorded at Putney station. You can barely see D6 on the surface in this photo.
SWE at SASP is now comparable to WY2012 amounts. Hopfully, addition SWE will be added during the forecasted April 19-21 storm.
Park Cone – April 16
Layers D2-5 are merged on the surface. Prior to D5, D2 was extremely mild, if present at all, at Park Cone. Given the light nature of D3/D4 at SASP, it is likely not much of these events contributed significantly to the dust seen at Park Cone. Hence, the majority of dust from D2-D5 is primarily from D5. However, this is where we get into the spatial variability of dust deposition in Central Colorado, through very reliable observations D2/D3 was on the surface of the snow in the Crested Butte area on April 1. In addition, D5 was observed in vast quantities as it was being deposited in the Vail area and also after it was deposited in significant quantities in the Aspen area. At the time of observation near Aspen on April 15, D5 was under 6-8” of snow and emerging to the surface quickly. Judging by these and other observations (March CODOS tour etc.) the severity and extent of D2-D5 is of significant severity in the West Elk and Maroon Bells region.
Snowpack is isothermal and rotten at Park Cone. Minor gain in snow height and moderate gain in SWE (3.2”) since the previous CODOS tour on March 16. All-layers-merged samples were taken at the pit location.
Park Cone is considered to have “Low” March 1st SWE and to be having a “Dry” spring with “Average” dust under our DERC classification. See the below DERC slideshows to find hydrographs from similar years.
Taylor River at Taylor Park (pdf)
East River at Almont (pdf)
Lake Fork at Gateway (pdf)
Looking north out over Taylor Reservoir, near Park Cone Sample location.
Dust on surface at Park Cone teeters between Min and Average, but considering dust deposition on a regional level pushes it over to the Average category.
Spring Creek – April 16
Snow is nearly gone in the area surrounding the pit location, which is currently the only patch of snow at this elevation across the landscape. SWE at the actual sample site is the same as March 16. Snowpack is isothermal and rotten. Dust is dark and D2-5 are merged on the surface (but not as severe as Wolf Creek). All-layers-merged samples were taken at the pit location.
Apart from the forecast showing a likelihood of precipitation April 19, it is reasonable to expect Spring Creek to continue losing it’s remaining snow to runoff soon. Spring Creek is considered to have “Low” March 1st SWE and to be having a “Dry” spring with “Average” dust under our DERC classification. See the below DERC slideshows to find hydrographs from similar years:
Lake Fork at Gateview (pdf)
Spring Creek CODOS site on April 16. Photo is looking up towards the sample location on the hillslope.
All layer are merged at Spring Creek. Overall not nearly as severe as Swamp Angel or Wolf Creek.
Photo looking at the San Juan Mts toward Lake City.
Wolf Creek Summit – April 16
Major losses in snow height and SWE were noted since the last CODOS tour. Oddly, or amazingly, snowdepth decreased by half since our last visit on March 16, from 4.8” to 2.4’. And SWE has decreased from 17” to 11”. Wolf Creek SNOTEL on the other hand, after having reached peak SWE on April 1, is the same on April 16 as it was on March 16 (19.2” of SWE).
Dust is highly visible across landscape and in the pit. Layers D2-5 are merged and on the surface. Dust is worse at this location than any other CODOS site. Snowpack is isothermal and very wet. The ground is extremely saturated and muddy.
The snowpack is shallow for Wolf Creek, considering the warm temperatures this entire season and lack of added precipitation, the melt we have seen so far, we expect snow to continue depleting rapidly. Within our DERC classification, Wolf Creek is classified as having “Low” March 1st SWE, “Average” dust and “Dry” springtime precipitation. Please see the below hydrographs for typical runoff patterns that have transpired in similar previous seasons in our period of record:
Preferential melt at Wolf Creek due to dust.
The landscape is starting to show bare ground at Wolf Creek Pass.
Wolf Creek has the worst dust conditions observed on the CODOS circuit. D2-D5 is at the surface of the snowpack, and unless adequately buried by spring storms will accelerate snowmelt and sublimation rates (further reducing runoff).
Berthoud Summit – April 11 and April 19
The CODOS snow profiles on April 11 revealed no dust within or on the snow to the naked eye. On April 19 we revisited the site to assess the presence of D5/D6. After revisiting the Front Range sites it is clear that D5 for sure is a statewide event. The dust is slightly underneath the surface or essentially on the surface around the sample area and is of significant severity. "Significant severity", meaning the dust is obvious and pronounced in the snowpack and on the surrounding landscape and will have a controlling influence on timing of snowpack warming, melt rates, and sublimation rates. Like all the other CODOS sites, D5 hits right near peak SWE accumulation, making it a nuisance the duration of snow melt season.
With the presence of D5 we are tweaking our classification of dust from "Min" to "Average". So currently, Berthoud CODOS site is classified as “Low” March 1 SWE, “Average” dust and “Wet” spring conditions. The link below contains plausible runoff scenarios. WY2012 offers a direct comparison to WY2018.
The snow profile at Berthoud looks much different on April 19 than it has all season. D5 is ~ 4" below the surface and is a very obvious and will be a significant influence on snow melt once it is entirely exposed across the landscape, which will be very soon.
At Berthoud Pass dust is very noticeable in depressions and eddies of the landscape.
Grizzly Peak/Loveland Pass – April 11 and April 19
On April 11 Grizzly Peak showed very mild dust from D2-D4 and light dust on the surface from possibly local sources. On April 19 D5 was on the surface, very dark and dirty in locations, and largely windswept.
We now have the Grizzly CODOS site classified as “Average” March 1 SWE, “Average” dust and “Average” spring conditions, to date. The link below contains plausible runoff scenarios based on similar hydrographs under similar conditions. There are no direct comparisons from previous years, but ’15 and '16 offers a nearest neighbor comparison.
Dust at Loveland Pass is visible in dune-like patterns.
Dust from D5 is essentially on the surface on the profile and surrounding landscape.
D5 under a surface crust at Loveland Pass
Another landscape photo from near CODOS sample site near Loveland Pass.
Hoosier Pass – April 11
Snow profile at Hoosier revealed very mild dust from D2-D4. The site was not revisited on April 19 due to lack of daylight and an approaching storm. Given the extent and severity of D5 across the state, including Aspen and Monarch Pass where there is moderate dust on the surface, we are assuming D5 is also present at Hoosier Pass and also of moderate severity.
Using the DERC approach WY2018 at Hoosier Pass has unfolded with “Average” March 1st SWE, “Average” Dust intensity, to date, and overall near “Average” spring precipitation, so far. In our March 1st Update we posted the following analysis of WY2018 that narrowed the DERC possibilities for Hoosier Pass to prior Water Years with “Average” March 1st SWE. 2010, 2012, and 2016 is a close comparison.
Willow Creek – April 11 and April 19
Willow Creek revealed no observable dust on April 11. On April 19 D5 was very apparant but slightly less intense as Berthoud. A bit of leaching had occurred at the surface as there was no clean snow capping the dust so more melt had occurred over the last week. Willow Creek teetered between "Min" dust and "Average" dust severity, but considering the dust observed on the landscape driving to Willow Creek - which is considerable - pushes the classification to the "Average" category.
Under the DERC approach, WY2018 at Willow Creek Pass has unfolded with “High” March 1st SWE, “Average” Dust intensity and “Wet” spring conditions, to date. In our March 1st Update we posted the following analysis of WY2018 that narrowed the DERC domain for Willow Creek Pass to prior water years with High March 1st SWE, WY2011, WY2014 offer the best comparison:
Dust visible in the foreground of the photo.
Looking at landscape near Willow Creek sample area.
Snow pit at Willow Creek. Dust at the surface. More melt has been occurring at this site and a bit of leaching of dust in the wet snowpack.
Rabbit Ears Pass – April 14
Rabbit Ears Pass has gained 15” in SWE since our March 14 visit and is also now isothermal. Dust was 7.8” below the surface and not visible on the landscape except at lower elevations. The dust within the snow pack is dark and very visible. D5 is ~12” above D3/D4, and D3/D4 is ~20” above D2 at this site.
Rabbit Ears and Northern Colorado in general have benefited nicely from recent April storms. This year, the Rabbit Ears SNOTEL was showing “Low” March 1st SWE under our DERC Classification framework and is currently showing “Average” dust. Precipitation wise Rabbit Ears is having a “Wet” spring. Yampa River hydrographs for other years with Low March 1st SWE are in the linked slideshow below:
The Rabbit Ears dust situation taken as a whole is average. It is one of the few areas very near average snowpack for the season.
Grand Mesa – April 14
All five of this seasons dust events have now been observed at Grand Mesa. D3-D5 is 14” below the snow surface, and D2 is 10” below D3-D5. Both dust layers are very evident in the snowpack and on the surface across the landscape where new snow had blown away. Dust is also on the surface at lower elevations. Snowpack deteriorates rapidly below 10,000 ft. Grand Mesa CODOS sample site gained 4.2” SWE since mid-March and the snowpack is isothermal.
With five observed dust events this site is solidly within our “Average” dust realm in the DERC model. March 1st SWE was classified at “Low” and so far the site is experiencing “Dry” spring precipitation. Links to Plateau and Surface Creek below contain DERC slideshows for downstream runoff in other “Low” March 1st SWE years.
Grand Mesa snow profile on April 14. D3-D5 is ~14" below the new snow accumulation. D2 is ~10" below D3-D5. The cards mark the dust layers
Fresh snow overlays D3-D5 by ~14, but it is on the surface at lower elevations
McClure Pass – April 15
Our March CODOS visit to McClure Pass revealed a very dirty D2 layer, springtime conditions and isothermal snowpack. Since then, the snowpack has fully depleted. The landscape surrounding the pass is dry. All-layers-merged samples were taken from isolated patches near the study site. We visited McClure on April 15, one of the few isolated patches remaining in the area was located right on top of the McClure SNOTEL pillow, on that day the SNOTEL was reporting 3.6” of SWE. Unfortunately, the picture we took of the pillow was lost.
McClure Pass was soundly in our “Low” March 1 SWE classification under our DERC framework this year. Dust in the region is “Average” and the site (obviously) is “Dry” spring conditions. The three DERC slideshows linked below are from downstream waterways and contain hydrographs from other years with “Low” March 1st SWE.
Photo looking up the McClure Pass near the CODOS sample locations.
Some snow can still be seen at the very tops of the surrounding mountains near McClure.
Weather & Climatology
The arid dust source regions of the Four Corners have been in an extreme or exceptional drought most of winter with conditions deteriorating incrementally. Staying consistent with the forecast this entire winter, the one month regional predictions are for well-above average temperatures and below median precipitation. As spring moves forward we will be watching both the mountains and the desert for changes in dust and dust available for transport.
On April 19th a closed low pressure system will enter the Four Corners region and if forecasts hold this system will deliver moderate snowfall to the mountains, along with strong winds. Prior to reaching the San Juans the system will track through Northern Arizona, our dust source region. While the desert will see a bit of rain it appears that the precipitation there will be preceded by fierce winds, and a dust storm warning has been issued. This warning will remain active through Thursday evening. Here in the San Juans we are anticipating more dust loading to accompany this storm system, so keep an eye out for potential alerts on this event.
Greetings from Silverton,
The morning of Thursday, April 12 started off with dust storm warnings in the desert southwest. We watched as web cameras showed the clouds and dust moving towards Colorado. In the Four Corners region high winds and dry dusty clouds were widely reported, folks could "taste" the dust in the air and feel the dust in their eyes. Phil Straub (CSAS employee) was at the Opus hut (San Juan Mts.) during the event and said it looked apocalyptic from about 4pm until the sun went down. The majority of the event was deposited dry in the San Juan Mts., without precipitation, on top of dust layers D3/D4 which were already on the surface of the snowpack. This event looks to be widespread with reliable reports describing a super dusty Vail Pass and Vail Mtn of red/brown/rust coloration. Even reports of dust on vehicles in Boulder. Starting around 8pm precipitation followed the dust and high winds, we received 0.5" (13 mm) of water content at Swamp Angel and snow is in the forecast the rest of today and tonight. Currently, D3/D4/D5 are combined into one layer and sitting ~7" below the snow surface at Swamp Angel. After the storm passes we will sample the dust at Swampy and get revealing pictures of the severity of the event.
The CODOS team conducted a portion of the April CODOS tour on April 11. Sites visited were on the Front Range, Hoosier, Grizzly, Berthoud, and Willow Creek Pass. We opted to delay sampling at the rest of the CODOS sites until after this current storm passes in order to assess the range and intensity of D5.
You can expect a full April CODOS Tour report by the first part of next week.
More from Silverton soon.
Photo taken by Phil Straub near Opus Hut in San Juan Mts
Abajo dust camera on April 12.
Picture taken by Phil Straub
Greetings from Silverton,
The Senator Beck Basin (SBB) received its fourth dust event of the season this week. From Sunday evening through Monday at midnight the Basin received a long duration dry event. This event was deposited directly on D3, which was still on the snow surface. D4 was a much stronger event than D3 and the two layers combined are now very evident in the snowpack. Being on the surface, their hydrologic implications are already in play. With incoming unsettled weather, we can expect them to be buried in the next few days, although not substantially.
CSAS will sample D3/4 today, and the merged layer will be analyzed for its composition and mass loading in the coming weeks. For now, the D4 wind rose is below and a picture of the dust and haze that composed this past event, taken on the morning Monday, April 2 from the Four Corners area.
Snowpack Conditions
Spring has sprung in the Senator Beck Basin. Yesterday, April 5th, the first isothermal snowpack temperatures of the season were recorded at Swamp Angel Study Plot (SASP). Isothermal snowpacks are 0° Celsius throughout the height of the snow, except the top 12" (30 cm) or so which is subject to diurnal temperature fluctuations.
Isothermal snowpacks are an important indication of the impending melt season, as it shows an acceleration in snowpack ripening, ripening is the process by which liquid water is introduced into the snowpack and percolates into the ground, and eventually into the waterways. It is not surprising to be finding isothermal snow at SASP given that in the past few days we have seen a slow increase in streamflow at our Senator Beck Stream Gauge (SBSG) for the first time this season.
Across the Senator Beck Basin, dust is sitting on the snowpack surface (merged layers D3 and D4) as well at 20-30 cm below the snow surface (D2). The exception is on south facing slopes, where layers D2-4 are all merged at the surface. These slopes, with their shallow snowpack and much more notable dust will melt at a faster rate than less solar aspects in the SBB and in the San Juan Mountains as a whole. Snow depth is highly variable across the region, so we can expect many slopes to melt out while others may hold snow into the early summer.
A Brief Weather Outlook
An atmospheric river event is impacting the Pacific Northwest currently and will move into the Rockies in the coming days. However, by the time the system makes it to Colorado it will be weak and scattered. We can expect intermittent and low intensity snow, although it is likely that a handful of specific areas will see notable snow totals. Because of the difficulty of predicting totals in these zonal events, the places where we might see higher snowfall totals are still a bit of a mystery.
Following the atmospheric river leftovers, the majority of Colorado can expect more of the warm and dry weather we’ve become so accustomed to. The end of next week looks windy with the possibility of a bit of precipitation. We’ll be on the lookout for snow and dust with any additional unsettled weather in the region.
The Colorado Basin River Forecast Center "Colorado Basin April Water Supply" webinar was held today, the presentation can be found at: https://www.cbrfc.noaa.gov/present/present2018.cgi. Encouragingly, they pointed out a couple possible active weather patterns towards mid-April that could add to the snowpack. Not to mention providing overcast skies, cooler temperatures, and keeping dust layers buried beneath the surface for as long as possible, delaying the bulk of snowmelt until a more normal time-frame.
Please see USGS plots below.
More from Silverton soon.
Above: Orange, hazy skies observed near the Four Corners region on April 2.
Below: For the stream gauges that are reporting, only a few are near median flows. Some gauges show the spike from the wet snow and rain event in latter March.
Greetings from Silverton,
Dust and Snowpack Conditions:
Late in the evening on April 1 orange and hazy skies were observed in Crested Butte and Ouray. Along with observations at SASP, D3 was also observed at the surface around the Crested Butte area. The dust cameras in the source region showed a bit of haze as well. Yesterday and last night we saw windy conditions and a couple inches of snow last night in the Northern San Juans. If a small amount of additional dust came in April 1 it may be hard to decipher from D3. A snow profile at SASP on April 1 show signs of the snowpack warming and wetting. Streamflow at Senator Beck (stream gauge at 11,000') has kicked in a bit (stage has increased 0.10') more since April 1. We will assess dust conditions more closely today/tomorrow and issue another update soon.
April 1 Snow Course Plots:
Now that we have just passed into the month of April I thought it would be interesting to investigate how this season’s April 1st SWE compared within the context of long-term snow course SWE values. And I like to remind folks whenever I get the chance of the difference between snow course data and SNOTEL data. In Colorado, many snow courses were established in the 1930’s/40’s, a data record of ~80 years. Snow courses are manual measurements collected with a Federal Sampler which, by weighing the Sampler containing a core from the snowpack, directly translates to inches of water in that column of snow. Snow courses usually involve ~10-15 SWE measurements over a transect so the averaged SWE value that is reported contains at least some component of the spatial variability of the landscape. The downside of snow courses is they require a person to take these measurements (time, money, safety, etc). Due to lack of funding/resources at NRCS many snow courses have been “adopted” by water entities and private businesses, so instead of seeing these valuable long-term data records being abandoned, collect the data on behalf of the NRCS. Lastly, snow course data is usually only collected at the first of the month during the spring (low temporal resolution). Automated SNOTEL stations on the other hand report on a daily basis, so you can look at the data on the computer every morning and see how bad/good the snowpack is doing. But SNOTEL SWE data is point data, meaning the SWE value comes from a “pillow” that essentially weighs the overlaying mass of snow (no integration of spatial variability). SNOTEL stations collect other beneficial information like precipitation, air temperature, snow depth, wind speed/direction. Many SNOTEL stations were established near snow course sites to correlate data records. Now that many SNOTEL stations have been in place 30-40 years, the data seems to be used and referenced much more frequently than snow course data, but is important to consider the value of snow course data.
Above: Considering the plot "Average of 81 Snow Courses Across Colorado", WY2018 is comparable to 1966, 1981, 1999, 2004, 2012. We are faring just very slightly better than 1977 and 2002. Fewer snow course data comprised the averages in the 1930/40's, more snow courses were operational by the 1950's. The trend lines for the two different time periods was an arbitrary grouping, but intended to show the decline in SWE over the last ~ 30 years.
Above: This low snow season is hitting Southern Colorado the hardest. WY2018 conditions are very similar to 1977 and 2002, and are slightly less than 1946, 1971, 1972, and 1999 SWE values. Again, fewer snow course data comprised the averages in the 1930/40's, more snow courses were operational by the 1950's. The trend lines for the two different time periods was an arbitrary grouping, but intended to show the decline in SWE over the last ~ 30 years.
Above: Along with changes in SWE we see a change when peak SWE occurs by ~20 days. Julian day 90 is April 1. Peak SWE in the early 1980's occurred around April 10, recently it occurs around the last week of March.
Above: This winter has been warm even based on our limited data record going back to 2005. Periods below the mean were short lived downward spikes.
HYDROCLIMATE TRENDS IN THE SAN JUANS
Discussing snowpack trends across the state of Colorado is a bit too much to take on in this Update. But a couple years ago, using the San Juan Mountains as the study area, my colleague Steven Fassnacht at CSU and I did a pretty simple analysis looking at air temperature and precipitation from three long-term climate stations as well as SNOTEL and snow course data across the San Juans in Colorado and New Mexico. Using the Regional Kendall Test for Trend we analyzed these variables for trends. If you live in the Rio Grande Basin I recommend reading a more recent analysis “Observed Changes in Climate and Streamflow on the Upper Rio Grande Basin” by U. New Mexico researchers.
Above: Annual precipitation shows decreasing trend of 2.6” over period of record (1931-2015) at Hermit climate station. For the period 1980-2015 the decrease is significant. The entire decrease in precipitation is seen only during the cold season (Oct-May). Results are similar for Telluride (significant trend) and less so for Silverton (not significant) climate stations.
Above: Average annual, minimum, and maximum air temperatures for Hermit climate station (9,000’). Significant increase in average minimum, and average annual, temperatures. Average maximum temperature increased but not significantly. Approximately 1.5 degree Celsius warming in the last 35 years. Nearby Telluride and Silverton climate stations reveal similar rising minimum temperature trends.
Above: Comparing two time periods, “early” (1982-1995) and “late” (2002-2015). Time periods were selected arbitrarily. April 1 SWE has decreased from the early to the later time series – significant for 2/3 of stations in study. 1982-2015 show a study region decrease of SWE of 5” for the 34 year period. Using both SNOTEL as well as snow course data both slopes agree in the relationship between the two time series. A similar analysis using the variable Peak SWE gave similar results. Locations with more SWE show an increased rate of decline of SWE.
Greetings from Silverton,
The Senator Beck Basin received its third dust on snow event of the season during the afternoon and evening or March 25th. D3 was a dry event (occurring without accompanying precipitation) which is currently sitting on the surface of the snowpack around Red Mountain Pass. While it appears to be a relatively light event in terms of dust loading, because it is on the surface it is a worrisome layer as we approach the melt season.
Dry DOS events tend to be patchy on a landscape scale because the dry dust on the surface is susceptible to redistribution by winds following deposition. Wet events which occur with precipitation tend to deposit dust in a more uniform layer across the landscape. It is unclear at this point how winds affected distribution of D3. What we do know is that the dust is visible and on the surface, which is always a good reason to keep close tabs on the snowpack.
Additionally, we are still unsure of how D3 was deposited on the statewide scale. During our next CODOS tour we will assess this distribution as we think about the potential impacts of dust on the melt season on the larger scale. This week we observed D2 being a bit more severe (compared to the eastern San Juans) and mostly exposed on the Telluride, San Miguel, side of the mountain. Currently D2 at SASP (11,000') is still ~16" below the surface, but has revealed itself more so in wind swept and shallower snowpack (lower elevation) areas.
Below is the wind rose for D3.
Senator Beck Basin
As we move into spring CSAS will be spending far more time at our local study plots in the Senator Beck Basin. We will be digging snow pits at the Swamp Angel Study Plot weekly and at our higher elevation Senator Beck Study Plot as often as weather allows. We have also installed our stream gauge at the basin pour point for the season, and hope to capture the full seasonal flow cycle for our basin. Those data will be available on our website.
In addition to monitoring dust and SWE in our study basin we are watching closely for Isothermal snowpack temperatures, which is a clear signal of the approaching melt season. We post all of our Senator Beck Basin snow pits on our website so you can track the snowpack progress here: http://www.codos.org/sbb/#snowprofiles-sbb
Streamflow
Most of the discharge sites that we monitor have not seen notable increases in streamflow yet this spring. As we move into spring we expect to see smaller and lower elevation streams and rivers respond to snowmelt first, followed by larger and/or higher rivers which take more water input or warmer temperatures to see significant flow increases. Many rivers have just begun to be gauged for the season, so while our statewide discharge dataset remains slim it is a useful tool for us in keeping tabs on statewide snowpack from here in Silverton.
One river that has seen a spike already this season in the Crystal River, which is gauged near Redstone. This surge in flow was likely caused by a rain event which would have coincided with our Winter Storm #11 here in the Senator Beck Basin. While this was in no way a major flooding event, it is a good example of the flow regimes that we are watching for as we move into spring.
Weather Outlook
With the entirety of the Southwest United States experiencing a severe drought any precipitation we can pick up in the Four Corners region will be much appreciated. Currently there is a large scale atmospheric river event building out in the North Pacific. There is good model agreement that suggests the majority of the Pacific coast will see heavy precipitation, with Washington and Oregon currently being favored significantly. What is still unclear is how far inland the storm will continue to deliver high intensity precipitation and where that precipitation will be at its heaviest. As AR events move inland they tend to become lower in intensity and also narrower in their impact, so the regions that receive major precipitation become more specific. As the system builds and moves closer to the West Coast there will hopefully be more clarity on what we can expect here in Colorado.
As discussed in previous CODOS updates this year, long range climate models are consistently suggesting that the Southwest US will see above average temperatures and below average precipitation. This coupled with the already severe drought conditions is a worrisome set-up from a few perspectives. First of all, it looks like the low snowpack plaguing much of Colorado will not have the chance to grow significantly as sometimes happens during the spring. Also, the dry desert seems as if it will stay dry through the melt season, which has us thinking about dust. Dry soils are far more available for transport and with soil moisture in the dust source region hovering near historic lows we are heads up for any significant wind event with West or Southwest flow.
Upcoming CODOS Tour
During the early April a CSAS team will be visiting our 11 CODOS sites to assess SWE and dust conditions statewide. This will be our second CODOS tour of the season (read the report from our first tour here: http://www.codos.org/codosupdates/march172017-tgc89)
During the first CODOS tour CSAS teams consistently found low snowpack and SWE conditions as well as two distinct dust layers within the snowpack at all of our established CODOS sites. Snowpack temperatures were within normal realms for the middle of march, but with low snowpack, warm temperatures and dust in the upper layers of the snow we expect to see many sites transition into an isothermal temperature regime soon. Isothermal snowpacks are at or very near 0° Celsius throughout the entirety of their height. This means that the snowpack has begun to melt and we expect to see the SWE in those snowpacks to decline and for liquid water to become far more present within the snowpack. We will assess snowpack temperatures along with SWE and dust presence during this upcoming CODOS tour. Look for our report on that tour sometime after next weekend.
A Final Note on Dust…
While we may not have had a severe dust event in Colorado yet this year, the dust is piling up in Eastern Europe. A serious Saharan dust event turned mountains in Russia and the Caucuses a ghastly orange color. Read about that otherworldly event here: https://www.npr.org/sections/thetwo-way/2018/03/26/596988671/clockwork-orange-why-russian-ski-slopes-are-being-blanketed-in-the-unearthly-col
Also, check out this dramatic avalanche which was initiated due to dust enhanced radiative forcing (dust lowering snow albedo and initiating a melt cycle): https://weather.com/storms/severe/video/avalanche-at-mt-elbrus-in-russia-buries-cars-in-parking-lot
That’s all for now. Check back here for more CODOS updates as spring pushes forward.
Greetings from Silverton,
As it started raining early last night and continued throughout the evening here in Silverton (this morning it is slowly turning to wet snow) I could not avoid the feeling that spring is really trying to rush things a bit. Add the scant snowcover and muddy streets and it definitely feels like late May and not late March. These conditions lead me to think of snow melt and streamflow and what could unfold this runoff season. In many areas of Colorado this snow season is being compared to the notorious low snowpack of WY2002, and indeed considering the graphs below WY2018 is tracking WY2002 snow conditions very closely. With this shot of precipitation we are currently receiving, and a bit going into next week, it is looking like we may be slightly be above WY2002 conditions statewide by April 1. Keeping a similar train of thought as in the March 9 CODOS Update the cumulative streamflow plots below show what unfolded in WY2002, and may give a sense of what we could see this year. In our CODOS report last week we included a table of snowpack temperatures from our March 14-17 tour. Results were generally comparable to the last four out of five years.
The one-month forecast remains boring. Colorado saw some decent storms this past week as we issued two storm reports for Senator Beck, and the 7-day outlook indicates ~1” of potential precipitation in the mountains, but the one-month outlook still calls for warms temperatures and below average chance of precipitation. See forecast images below.
DUST: High winds in Utah on a couple different occasions this week had us wondering if we would see dust in the Colorado mountains. The snowpack at SASP did not reveal any new dust and D2 is still at least 12" below surface. We will keep an eye out and report any new developments ASAP. It will be interesting to see how these next couple of months develop in terms of spring weather, dust conditions, and resultant streamflow. Will we see some gains in snowpack going into April? If spring is warm and dry, how early will snowmelt begin? To what degree will dust conditions advance an already potentially early melt season?
Stream gauge at Senator Beck Study Basin. The weir is under the ice on the left hand side of photograph. The staff gauge reads from the bottom of the weir notch. In early winter water continued to flow, freeze and accumulate to 1.6' on the staff gauge. We pick axed through 1' of ice to free the sensors and expose the stream underneath, which is flowing. The next step is to continue removing the ice so the sensors can be installed. This weir has been in place for 12 years and it is possible the structure and bed have morphed, so starting this summer we will gauge the stream to check accuracy of the weir and if need be develop a new stage/discharge relationship curve.
Streamflow timing indices were calculated based on cumulative flow from March 1 thru June 30, this time period captures the dominant snowmelt portion of the hydrograph for most rivers in Colorado. WY2002 was compared to the median for the San Juan, Animas, Rio Grande, Taylor, and Uncompahgre rivers. Indices calculated are Q20, Q50, and Q80, corresponding to 20%, 50%, and 80% of cumulative flow having passed the stream gauge. These values approximate the beginning, middle, and end of the snowmelt period. From left to right, the red and black vertical lines indicate Q20, Q50, Q80, respectively, for WY2002 (red) and the median (black)
From left to right, the red and black vertical lines indicate Q20, Q50, Q80, respectively, for WY2002 (red) and the median (black). Compared to the median, in WY2002 snowmelt runoff began a month early, but early season melt (# days from Q20 to Q50) was longer (38 days compared to the median of 27 days). Q50 occurred 17 days early compared to median. And Q80 was about 12 days early. In WY2002, Q20 to Q80 was 59 days, compared to the median of 43 days.
Snowmelt runoff began nearly 2 months early in the Rio Grande in WY2002, like the Uncompahgre runoff took place over a longer time-frame. Q50 was over 5 weeks earlier than the median. The bulk of snow melt streamflow was over before the month of June.
The San Juan was about a month early in seeing the start of snow melt runoff. The mid-point for WY2002 occurred when median Q20 typically begins. From Q20 to Q80 WY2002 was more compressed compared to the Rio Grande and Uncompahgre.
For the Taylor Q20 happened 3 weeks earlier than the norm. Q50 happened 15 days early. And the bulk of snowmelt runoff was completed by the first week of June.
Q20 began mid-April compared to the median of May 5. Q50 was about 15 days early, and the bulk of snowmelt runoff was completed the first week of June compared to the norm of mid-June.
SUMMARY
A storm on March 5th brought Colorado’s first dust-on-snow event of WY2017 (D1-WY2017). Winds up to 100 mph were recorded in the San Juan Mountains. The preceding months experienced a large number of high wind events, but the March 5th event contained the right elements to mobilize dust in the source area and transport it to the Colorado Mountains. From March 13-14 CODOS personnel toured our 11 samples sites around the state documenting the presence/absence of dust. Dust was observed at 7 CODOS sites, following a general south to north gradient of moderate intensity at SASP, Wolf Cr., Spring Cr., Park Cone, McClure Pass, Hoosier Pass, and Loveland Pass. Dust was not apparent at Grand Mesa, Rabbit Ears Pass, Willow Cr. Pass, and Berthoud Pass. With the continuous dry, warm, and sunny conditions since March 5th, and the forecast indicating more of the same, combined with D1 being located on the surface of the snowpack increasing the absorption of solar radiation, sets up the conditions where the snowpack has experienced accelerated warming and melt, which will continue until the next chances of precipitation and cooler weather arrive. SNOTEL station snow water equivalent (SWE) data indicate major basins in Colorado are still in the “High” category, as defined by the CODOS Dust Enhanced Runoff Classification (DERC “Average” equals day median +/- 10%). For gauging stations that are active this time of year, streamflow is showing an early season uptick in response to the last ten days of sunny/warm conditions. In the southern part of Colorado some streams are running double their median discharge for this time of year, with two stations (Dolores at Dolores, San Juan at Pagosa) showing flows close to 4 times their normal rate.
Greetings from Silverton,
Here in Senator Beck we are working to start-up our stream gage very soon if it is possible to remove the ice in the weir. I am sure the warm temperatures predicted this month will lend a hand. The weir is located at the pour point of our watershed at 11,000'. Due to the low flows in the stream going into winter (low thermal mass), the lack of insulating snow, and cold evenings in early winter, the small mountain stream froze up pretty good. Last year, the month of March was the warmest March on record (going back 123 years). This resulted in snow at lower elevations melting and the snowpack at higher elevations warming rapidly, at SASP the snowpack reached isothermal conditions (0 degrees throughout) earlier than we have observed before (http://www.codos.org/codosupdates/mar242017). Of course last year we had lots of snow going into March that was available for melt and by the end of March a MODIS image of snow cover looked a lot different than it did at the beginning. This year there is no, or very little, snow at lower elevations to melt. A record low snowpack at higher elevations, lack of storm events to-date and forecasted into the near future, and very warm temperatures dominating this entire winter season, the question is how early and fast will we see snowpack warming and subsequent melt? Exploring this question using our somewhat limited streamflow data-set that reaches back to WY2006 is the goal of the following graphs, with possibly helping understand what might be plausible in nearby watersheds.
SBB streamflow timing indices were calculated based on cumulative flow from the start of the season (typically in March, base flow adjustments are also made) thru June 30, this time period captures the dominant snowmelt portion of our high elevation hydrograph. Indices calculated are Q20, Q50, and Q80, corresponding to 20%, 50%, and 80% of cumulative flow having passed the stream gage. These values have been used to approximate the beginning, middle, and end of the snowmelt period in other studies (Clowe 2010). The plot below compares Peak SWE at SASP and the date Q20 occurred. In general, even though dust and spring conditions can alter this assumption, a low Peak SWE equates to an early start to the snowmelt period.
Peak SWE compared with date of Q20 (20% of spring cumulative flow has occurred). Blue indicates a low dust year, yellow indicates a medium dust year, and red a heavy dust year. Q50 and Q80 were also calculated (not shown), this relationship with Peak SWE breaks down as melt season progresses and spring/dust conditions dominate. Current SWE at SASP is 12.2", if only modest gains are made over the next few weeks what could this mean in terms of snowmelt onset this melt season? In 2002 (see image below) at Red Mt SNOTEL snow was all gone about a month earlier than the median time-frame.
Data shows the typical number of days between Peak SWE and Q20 varies from 1-35 days. But there are oddball years like WY2015 where it was -21 days due to snowmelt starting early but then large late season accumulation occurred. Unfortunately WY2002 is not in our data record at SBB because it would be a very helpful comparison. But Red Mt. SNOTEL currently shows essentially the same value at this point in 2002. Peak SWE in 2002 was March 29. In 2002 there was an additional ~3” gain in SWE the latter half of March. This year, May shows a few good chances of precipitation but overall the forecast is warm with below normal precipitation.
WY2002 at Red Mt SNOTEL. SWE amounts today are about what they were in 2002. In 2002 an additional ~3" SWE accumulated the last two-thirds of March. .
Current conditions at Red Mt SNOTEL. SWE at SASP (1 mile from Red Mt) is 12.2"
Another item we will be keeping an eye on this runoff season is the relatively strong relationship between snow-all-gone at SASP and the occurrence of Q50. So far in our POR when snow leaves the landscape at SASP (11,000’) then within 0-12 days (average of 3 days) 50% of snowmelt runoff has occurred. It is more typical to see Q50 a couple days before SAG at SASP. Please see plot below:
As a reminder we document melt rates, days to snow-all-gone, and other summary statistics for the SNOTEL stations that comprise our CODOS sample sites across Colorado (http://www.codos.org/sbb/#snowmelt-sbb). This season in particular it would be worthwhile reviewing these data as a range of possibilities for your watershed of interest. Also too, there is the DERC scenarios that were published in the May 1 Update (http://www.codos.org/codosupdates/mar12017-7pbef).
So far from indications at SASP and surrounding area, dust event D2 is still located below the snow surface and not contributing to increased warming of the snowpack. We will issue an alert if/when this changes.
The Colorado Basin River Forecast Center (CBRFC) held the March water supply webinar on March 7, https://www.cbrfc.noaa.gov/present/2018/cowsupmar2018.pdf. This presentation is worth reviewing as we head into spring. Given the weather forecast (also in the briefing), the water supply forecast is expected to trend downward. Another good point made in the meeting is the reminder that March and the first couple weeks of April are crucial if further gains in the snowpack are going to be made. Even though in WY2015 we experienced the “miracle May” that turned around a dismal snowpack, and May has been wetter than normal the last few years, historically the chances are not great that we are going to make up much ground.
On the Colorado Climate's "NIDIS: Upper Colorado River Regional Drought Early Warning System" teleconference on March 6 (http://climate.colostate.edu/~drought/current_assessment.php), came reports from the north-central mountains indicating at elevations lower than the SNOTEL elevation monitoring range (few stations located below ~9,200'), less snow (and even no snow) is being observed. Indicating that, where in the past we may have benefited from snow accumulation at these foothill elevation levels, may not be the case this year.
Also on the call came reports across Colorado from agricultural communities that the scant precipitation they might have received over the last few weeks was not retained to any degree. Agricultural and farm communities are reporting very dry soils (dry 3' down) made even dryer by the intense high winds of late. These winds have also kicked up dust storms and dry conditions have also resulted in wild fires. In Montezuma County in Southwest Colorado, reports of precipitation below ~9,300' is not sticking around and has/is melting, and hastened due to dust from local and regional sources accelerating melt.
More Soon
SUMMARY
Colorado has begun March with “high” conditions completely dominating the range of snowpack conditions among major basins across the Colorado Mountains. This update summarizes snowpack conditions state-wide and evaluates March 1st snow water equivalent (SWE) data from SNOTEL stations associated with our eleven CODOS sites and places them within the framework of the Dust Enhanced Runoff Classification scheme (DERC) developed by CODOS. A summary is presented by individual Basin, and provides a site-specific analyses for each CODOS site (linked below).
