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CODOS Update, May 21: Dust Covered by 1' of Snow. 1.7" Additional SWE at SBB

CODOS Update, May 21: Dust Covered by 1' of Snow. 1.7" Additional SWE at SBB

Colorado is now solidly in the melt season with decreases in SWE in most parts of the state. Recent significant snowfall has slowed snowmelt driven runoff, but most CODOS sites statewide are well past peak SWE for the season, and it is likely that snowpack is increasing only at the very highest altitudes. In the Senator Beck Basin we are seeing losses in total SWE up to above 12,000 ft., even with this most recent snowfall.

In the last few days much of the state received significant snowfall as a large low-pressure system moved through the region. Here in the Senator Beck Basin we saw over a foot of snow with 1.4 inches of water, and similar values for precipitation are seen statewide.

Prior to this storm, merged dust events D1-4 were on the surface and notably lowering snow albedo. Additionally, snowpack in the Senator Beck Basin is mostly isothermal, meaning that higher elevation snowpack is beginning to contribute to runoff. For the time being, this new snow will cover the dust and raise the snow albedo again. This re-burying of the dust, along with cooler temperatures, is evident in hydrographs statewide, with discharge steadily decreasing across the region for the past few days. Currently discharge is slightly below median value for this date at nearly all locations in Colorado.
 

CODOS Update: May 17th

CODOS Update: May 17th

Greetings from Silverton,

Since our last CODOS update on May 9, streamflow at Senator Beck saw a 3 day down-tick (where we saw 1" of additional precipitation), followed by a 5 day up-tick when nicer weather returned.  As I write this Update, snow is lightly falling at Red Mountain Pass and in Silverton the sparse flakes do not accumulate and barely wet the ground.  However, the fresh snow and overcast, cooler temperatures, which is forecasted to intensify and continue the remainder of this week, will again slow snowmelt and consequently reduce streamflows temporarily.  The expected precipitation in northeast quadrant of the state is impressive, but the entire state looks to benefit from additional precipitation over the next few days.  Dry conditions are expected to return on Saturday as a warming trend takes hold for 2-3 days.  And encouragingly, the 1-month forecast calls for an increased chance of above normal precipitation.  SNOTEL data are showing major basins are still staying very near median values.

May 5-6 WY2017 CODOS Tour Update

May 5-6 WY2017 CODOS Tour Update

Summary

The CSAS team conducted another statewide CODOS tour May 5-6.  Fortunately we documented no new dust events over the last 4 weeks.  So far this season we have documented a total of 4 dust events, tying WY2015 for the least number of dust events observed.  However, it’s not so much the number of events that matter but the severity and timing of the events.  It just takes one moderate/severe event, deposited toward the end of the accumulation season to drastically effect snowmelt timing and rate for the remainder of the snow season.  So far this year, D3 (moderate) and D4 (upper end of moderate), occurred during this timeframe (March 31 and April 9), when maximum snow accumulation is largely reached in most watersheds, thereby allowing the dust to remain near or on the surface throughout ablation.  And as we like to mention often, spring conditions play a large role in determining when and how long the dust is exposed.  For example, since D3/D4 we have seen a number of stormy periods bringing additional snow accumulation, overcast and cooler temperatures, which temporarily cover the dust and slow snowpack warming and melt.  April is typically the month where we see the most dust events, then March, then May.  Even with April behind us, the dust-on-snow season is far from over.  Any dust events that were to happen now would immediately be exposed, or within a couple days, on the surface of the snowpack, adding to the dust presently on snow surface, further reducing albedo and increasing snowmelt rates.

Breaking News:  As of this writing a long duration dust event was observed in the Grand Junction area late afternoon on May 7th, the remnants of which have been noted in the Roaring Fork Valley.  Station data in the source area show sustained wind gusts from May 6-7, and webcams indicate dust in the Monticello region.  So, it looks possible dust event #5 has arrived in some locales (this morning observations at SBB reveal no new dust deposition), a day after the CODOS tour was completed (much like D4 on April 9).  Expect more information as to the severity and spatial extent of this potential dust event once field data and observations are collected.        

SNOTEL data indicate major Colorado basins are near their long term median SWE with streamflows, showing a spike from the hot weather these past 6 days, are still mostly considered within their median range.  The forecast is calling for more variable weather with plenty of chances of precipitation with cooler temperatures.  Please see streamflow and forecast discussion below.    

Colorado Dust-on-Snow Conditions

Dust conditions around the state were mostly how we left it from our last CODOS tour April 7-9.  Colorado has not received any new dust events over the last month, albeit we possibly experienced one or two “haze” events in some locales, which, if any minor deposition occurred at all, it would be indistinguishable from the dust already on the surface of the snowpack.  To recap the four dust events this year; dust event #1 (D1) occurred on March 5, and D2 occurred on March 23, both of these events were very light and mostly unnoticeable for a few days after deposited until finally showing itself throughout the landscape.  D3 came in on March 31 and classified as moderate at SASP.  On April 9, the last day of our CODOS tour, a large part of Colorado received D4, which is considered to be in the upper end of moderate to lower end of severe category.  D4 was a “dry” event being transported and deposited without precipitation.  Dry events are characteristically deposited in preferential locations wherever the wind transports and releases the dust, such as depressions on the snow surface, leeward slopes, and treed depressions.  Some locales came out of the last 10 days of April with dust layers covered under a few inches of new snow, other areas like the Rio Grande basin did not see much, or any accumulation, so dust was already exposed when the warming trend over the last few days started.  Currently, at most CODOS sample sites, dust layers are now merged at the surface.           

Changes in dust conditions, however, were observed at Berthoud and Willow Creek where, either through receiving indistinguishable amounts of just one dust event or all four, over time with snowmelt has allowed this light dust to coalesce at the surface, making it visible across the landscape.  This dust does not change the “minimum” dust classification at these sites, but will play its usual role in reducing albedo and increasing the amount of solar energy absorbed into the snowpack.  In the table below we summarize snowpack and dust conditions as well as provide plausible prior year hydrographs, updated from what was reported last month, that might help shed light on what to expect the remainder of this snowmelt season.   Links to these hydrographs are available at the bottom of this report.  

CODOS Update

CODOS Update

Greetings from Silverton, 

The series of storm systems beginning April 24 that tapped the brakes on a rapid snowmelt, as well as added a bit more SWE to the snowpack, is due to phase out by Tuesday.  The last ten days of April precipitation favored the northern mountains, with Rabbit Ears SNOTEL seeing 3.6” SWE, Grizzly Peak near Loveland Pass gaining 1.2”, Scholfield 1.4”, Grand Mesa 0.6”, and Red Mountain Pass 1.0”.  Some locations saw a decrease in SWE, such as Park Cone (-0.9”) and Wolf Creek (-1.2”).      

CODOS Update April 24: Dust Conditions, Snowmelt Rates, & Unsettled Weather in Forecast

CODOS Update April 24: Dust Conditions, Snowmelt Rates, & Unsettled Weather in Forecast

As forecasted, the last ~19 days have been sunny, unseasonably warm, and mostly dry.  After a mostly warm March the snowpack statewide was 108% of normal.  Now, after a mostly warm/dry first two-thirds of April, average statewide snowpack conditions are 94% of normal.  When the heat was on the snowpack quickly responded.  In March, enthusiastic snowmelt was seen throughout the state and for a period it appeared most basins had seen peak SWE around March 1.  However a series of late March storms bumped SWE amounts creating a "double peak", with the second peak in most basins occurring around April 1.  Since April 1st we have seen rather high ablation rates.  Please see plots below investigating these warm conditions and increased snowmelt rates.    

No new dust events have occurred since the dry dust event (D4) on April 9. Dust layers D3/D4 have been exposed at the surface of the snowpack essentially since D4 was deposited. D4 was a dry event, occurring without accompanying precipitation. Dry dust events are more subject to preferential transport, meaning dust is deposited in thicker layers on lee aspects and in depressions in the snow surface such as old wind features. A haze event was observed April 14 but did not deposit a discernible amount of dust on the already exposed D3/D4 dust layers.  On April 20-21 we received a couple inches of new snow accumulation with 0.35" (9 mm) of precipitation.  This minor storm event provided an albedo reset and cooler temperatures over the last few days.  Now, at Red Mountain Pass D3/D4 is reemerged at the surface of the snowpack, and the patchier distribution of the dry D4 event along with the uniform distribution of D3 are both evident across the landscape.  Elsewhere around the state, with somewhat similar weather across mountain areas, conditions have likely unfolded in a similar manner where dust deposition was present (please see our April Tour Update http://www.codos.org/codosupdates/apr122017).   

 

Starting Monday, the forecast is calling for "unsettled weather" for the next ~6 days.  The result will be periods of showers, isolated thunderstorms, mountain snow, and at least cloudy conditions between storm systems.  Temperatures are expected to be below normal with the possibility of the snow line getting down to mountain bases.  With this expected precipitation it will be interesting what kind of third bump we'll see in the snowpack, the 7-day forecast calls for 1-2" of precipitation across Colorado, with northeast Colorado looking to finally receive some much needed precipitation .  It will also be interesting what sort of conditions May will bring, the last two years the month of May has been wet and cooler than normal, which was crucial not only in adding valuable SWE but also extending the snowmelt season to a near normal time-frame

CODOS Update: April 14 Haze, Chance of Precip in Forecast

CODOS Update: April 14 Haze, Chance of Precip in Forecast

Greetings from Silverton,

The past 6 days has seen an uptick in streamflow (some streams seeing close to double their median discharge) due to the warm/sunny conditions throughout most of Colorado with melt rates being exacerbated due to dust event D3 and/or D4 being located at the surface of the snowpack.  Around Red Mountain Pass, D3 and D4 are now merged in many locations and very close to merged at Swamp Angel.  During this time there have been a couple of windy days with gusts in the 20-30 mph range in the desert southwest, four corners region.  On Friday, April 14, these winds created enough disturbance to create a haze event in southwest Colorado.  Any dust that fell on the snow surface from this haze is likely negligible, as well as indecipherable with D3/D4 being located on the surface.  But, it is worth mentioning since these seemingly small events do incrementally add to the total dust load on the snow surface and contribute to further reduction of surface albedo.  

The forecast the next ~10 days is calling for a series of Pacific storms moving across the inter-mountain west.  Today winds will remain out of the southwest with strong gusts up north and lessening in the south, and warm temperatures continuing.  On Tuesday clouds will increase in the afternoon and bring chance of showers and maybe a few thunderstorms.  Snow levels could be in the 9,000' range Tuesday night.  Late Wednesday could see moderate accumulation in northern Colorado mountains and light accumulation in the central and southern mountains.  Another, slightly colder, system is due to move in Thursday thru Saturday continuing the chance of mountain snow and rain in the lower elevations.  All told, these systems are expected to bring periods with cloud cover and chance of precipitation, when these conditions occur will serve to lessen the solar energy input on the snowpack and possibly even cover the snow surface with clean, fresh snow, temporarily restoring high albedo to the snow surface.       

April 7-9 WY2017 CODOS Tour Update

April 7-9 WY2017 CODOS Tour Update

Summary

The CSAS team conducted the April CODOS tour April 7-9.  Dust event D3 is within the top 12” of the snowpack at the majority of CODOS sites, and as we were finishing the tour dust event D4, a dry deposition event that occurred April 9, was observed at Red Mt. Pass and Grande Mesa.  Judging by its intensity and the fact that it made it to Grande Mesa indicate chances are highly likely it is also at Wolf Creek, Spring Creek, Park Cone and McClure Pass.  Being the last storm system we received, and also being a mostly dry event, it is currently on the surface of the snowpack where it was deposited.   Locations that appeared to be dust free on April 9 are Willow Creek Pass and Berthoud Pass.  Loveland Pass received D1/D2 events but appears to not have received D3 or D4.  Hoosier Pass escaped D3 but it is uncertain if D4 reached that locale. 

At the onset of spring all of our CODOS sites boasted healthy above average snowpacks. Over our past two CODOS tours we have seen snowpack declines at many sites, with some significant losses in snow depth and snow water equivalent (SWE). Losses between the two CODOS tours were especially apparent at lower elevation sites and at sites with more dust deposition or dust at the surface of the snowpack.

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 WY2006-2016 are collated and presented to help with ascertaining what this Spring runoff scenario might look like.  We anticipate at least one additional circuit of our ten CODOS sites this season as well as intensive monitoring at Senator Beck Basin (SBB).

CODOS Dust Alert: Event D4 WY2017

CODOS Dust Alert: Event D4 WY2017

Greetings from Silverton.

CSAS was on the road over this past weekend for our second CODOS tour of the season. We will be releasing a full report on this data collection trip in the next couple days, but for the time being we have received another dust event at our Senator Beck Basin Study Area in the San Juan Mountains.

Our fourth dust event of the year was a moderate dry event, lasting approximately 21 hours. The majority of the dust was likely deposited toward the end of this period. Currently dust is most apparent on North and East facing slopes in leeward areas where air tends to recirculate when wind blows over the landscape. The dust is also highly visible in other small surface features such as old ski tracks and tree wells.

CODOS Dust Alert: Event D3 WY2017

CODOS Dust Alert: Event D3 WY2017

Winter storm #22 is now at its end and it was evident at the onset of the storm that this precipitation was accompanied by our third dust event of the season.

D3 was a “wet” event (occurring with precipitation) that began March 30th at 1500 and lasted 15 hours, ending at 0500 on March 31st.  The dust is pinkish-red in color was deposited in a very visible layer that is diffuse in the lower 2-3 cm of snow from winter storm #22. Winds during the event were largely from the south and southwest. This is our most visible dust event so far this season, and likely our largest by mass load as well.

CODOS Update: Event D2, Snowpack at Swamp Angel Isothermal

CODOS Update: Event D2, Snowpack at Swamp Angel Isothermal

The set-up of the storm currently passing through Colorado was perfect for bringing dust to the Colorado snowpack.  Dust event #2 (D2) hit the San Juan Mountains near Red Mountain Pass yesterday, March 23.  Like D1, this event came with snowfall and is difficult to currently see, being diffuse in the new snow accumulation.  The wonderfully productive storm that brought dust also deposited 18" of snow containing 1.5" water at SASP.  We will elaborate on this dust event as conditions unfold and ascertain the spatial extent during out next CODOS tour in mid-April.  Since the majority of the dust likely came at the beginning of the storm, it won't take long to blend with D1 once the snow warms and consolidates.  And fortunately for the time-being we have 18" of new snow covering D1 and most of D2.  Eventually, the dust will become more prominent and concentrated at the surface when sunny conditions return.

Along with this dust event, finally, we are seeing a reprieve from the dry, warm, and sunny stretch of weather we have been experiencing since the last storm (and dust event) March 5-6.  Even though we have only logged one moderate dust event prior to today,  when the dust is exposed on the surface of the snowpack like D1, it only serves to increase the absorption of solar radiation that contributes to warming/melting the snowpack.  This is the time of year when we play the "albedo reset" game, where we pray for new snowfall to cover dust accumulated at the surface of the snowpack, to keep the albedo (or reflectance) of the snow surface high, thereby slowing warming and subsequent melting of the snowpack.  At the least we are grateful to see cloudy, overcast conditions that limit the amount of incoming solar radiation.    

CODOS Update

CODOS Update

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.  

CODOS Dust Alert - Event D1 WY2017

CODOS Dust Alert - Event D1 WY2017

Greetings from Silverton,  

After a number of days since a storm that brought very high winds straight out of the desert southwest, dust is starting to show itself in some areas around the San Juan Mountains.  Observers reported dust mobilization in the source region, as far North as the Mexican Water/Kayenta country all the way down to Cameron, at the beginning of the storm on March 5.  With these field reports along with the high winds at Senator Beck we were fulling expecting to be reporting on Dust Event #1 immediately following the storm.  Initially however, the landscape, and snow profiles at SASP (and elsewhere) failed to show dust. 

In the Northern San Juans, this mild and diffuse dust event is still not yet showing on many NW-N aspects or in snow profiles at SASP, but has started to show on the surface of sunnier slopes where warming over last 5 days has allowed it to concentrate at the surface.  And it is more evident in "eddy" locations throughout the landscape.  

Samples of this "wet" event (occurring with precip) have been collected and we will report the mass loading from this event soon.  As mentioned a few days ago, the CODOS team will conduct the state-wide sampling tour starting on Monday and will report findings soon after. 

Senator Beck Basin-Wide SWE Estimations For February

Senator Beck Basin-Wide SWE Estimations For February

February 26 marked the final day of the NASA sponsored SnowEx campaign in Senator Beck Basin.  SnowEx, which included an intensive snow data collection effort February 6-10 and February 20-26 in SBB, is a multi-year project aimed at developing a snow-sensing satellite to measure snow water equivalent on a global scale.  During the study period, airborne snow measurements using many different instruments and methods were conducted over SBB.  While measurements were being made from the air, scientists on the ground collected snowpack information to "ground-truth" airborne data (https://snow.nasa.gov/snowex).  

 

Over 30 snow pits were excavated throughout the entire Basin to assess snowpack variables, including depth, density, SWE, temperature profile, grain types, and layer hardness.  Summary data from these snow profiles are now included in the March 1st Update on the CODOS website (http://www.codos.org/codosupdates/mar12017).  If you would like more information about this data please contact me.  Please keep in mind this is preliminary data and subject to corrections.

CODOS Update: March 1 SWE Conditions

CODOS Update: March 1 SWE Conditions

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). 

Dust Free So Far and Healthy Snowpack

Dust Free So Far and Healthy Snowpack

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’.

Center for Snow Update: November 1st, 2016

Center for Snow Update: November 1st, 2016

Greetings from Silverton, Colorado - 

I hope our readers had a very enjoyable summer/fall.  The summer flew by here at Center for Snow and Avalanche Studies catching up on projects that got pushed aside while we were monitoring the spring snowpack, performing summer station maintenance, and preparing for the coming winter.  I was hoping this beginning of the snow season update would coincide with a storm report detailing a big event to kick off WY2016.  But, unfortunately the month of October in the San Juan Mountains has been a bit dry.  Measured precipitation the month of October at the Swamp Angel Study Plot in our Senator Beck Study Basin (SBSB) was 0.75 (19 mm).  At Red Mountain SNOTEL, located exactly 1-mile the way the crow flies, measured precipitation was 0.60" (15 mm). We saw some nice precipitation events in August and September, some of which included snow at higher elevations but have since melted.  These Aug/Sept precipitation events resulted in bumps in streamflow higher than the norm, but currently we are seeing discharge a tad below normal. Concurrently, soil moisture conditions are in lower percentiles throughout most of the State.       

WY 2016 Season Summary

WY 2016 Season Summary

The result of a “Godzilla” El Nino year was basically an overall average statewide snowpack.  The entire state started off WY2016 with a bang building the snowpack at a higher rate than average Oct/Nov/Dec/Jan.  In February conditions took a turn for the worse with dry/warm weather lasting until mid-March for northern Colorado, and being much more severe and lasting until latter March for southern Colorado.  Northern locales recovered nicely from this dry stretch but the Rio Grande, Gunnison, and Animas/Dolores struggled the remainder of the season.  The month of May was generally overcast, cooler than average, and brought multiple precipitation events, putting a damper on snowmelt until conditions turned very warm the very end of May.  Many streams in southern Colorado saw peak discharge, well above their median values, around the June 5-10 timeframe.   

June 13 Update: Snow All Gone at SASP, Wolf Creek, and Grand Mesa

June 13 Update: Snow All Gone at SASP, Wolf Creek, and Grand Mesa

Greetings from Silverton,

Site visits to CODOS study plots at Grand Mesa on June 7, Swamp Angel Study Plot (SASP) on June 9, and Wolf Creek on June 10, revealed snow-all-gone (SAG) at all locations.  As the photos shown below illustrate, snow is either totally gone (Wolf Cr.) or exists only in thin, patchy areas.  Snow is mostly present in heavily treed areas and higher elevations, and predominately on northerly aspects.  All dust layers are merged at the surface of the snow.  Just like the other CODOS sites with dust, an “all-layers-merged” (ALM) sample was collected at each of these locations and sent to our USGS collaborators for chemical analyses for inter-site comparison.

June 3 Update – Central and Northern CODOS Site Visit

June 3 Update – Central and Northern CODOS Site Visit

SUMMARY

Final CODOS visits were conducted at Grizzly Peak (Loveland Pass), Hoosier, Berthoud, and Willow Creek Pass on Wednesday, June 1.  During this CODOS tour, comparatively weak dust-on-snow, likely from event D5, was observed at all sites except Willow Creek.  “All layers merged” (ALM) samples of this dust were collected at Berthoud Pass, Grizzly Peak, and Hoosier Pass.  These ALM samples were sent to our USGS collaborators for chemical and other analyses, for inter-site comparisons.

DUST-ON-SNOW CONDITIONS

During this CODOS circuit of Hoosier, Grizzly Peak (Loveland Pass), Berthoud, and Willow Creek Pass dust was observed at the snowpack surface on all aspects and elevations besides in the vicinity of Willow Creek.  All of these sites went the majority of winter without receiving dust until likely D5 (and D4 at Hoosier Pass), occurring on April 23, since that was the only significant dust event since the last CODOS trip.  Dust was barely distinguishable on the landscape and, if viewed from a distance, the snowcover appeared “clean”.  But dust was easily noticeable where ski tracks, sluffing, or avalanches disturbed the snow surface, exposing the clean snow underneath.  To the southwest, surface dust loadings appear greater along the Collegiate Peaks and near Monarch Pass.  This all means a slight but still meaningful reduction in snow albedo and accompanying increased absorption of solar radiation for the remainder of the snowmelt period.

WILLOW CREEK PASS:

The Willow Creek Pass CODOS snow profile site in the foreground, completely clear of snow.  Willow Creek Pass SNOTEL, located in the trees in the far part of the picture, shows 5” of remaining SWE.

Willow Creek Pass CODOS sample area. Besides north facing, heavily treed areas, snowcover has mostly retreated to higher elevations.

Willow Creek Pass looking towards Parkview Mountain.

BERTHOUD PASS:

Berthoud Pass CODOS sample site.  The beginnings of the snow pit show the contrast between the slightly dusty snow surface and the cleaner snow underneath.  

Berthoud Pass CODOS sample area.  Higher concentrations of dust are seen in slight depressions of the snow surface.

LOVELAND PASS (GRIZZLY PEAK):

Grizzly Peak CODOS snow profile. 

Picture taken from Grizzly Peak sample site on June 1.  About 1.5’ of snow depth (6.6” of SWE) remains at the CODOS site, located in a clearing a few hundred feet from Grizzly SNOTEL, next to the tower visible in the background.  Grizzly SNOTEL reported 5.4” of SWE on June 1.  Over the past 8 days since May 26, SWE has decreased a total of 5”.

Loveland Pass on June 1.  With thinning snowcover, solar radiation absorbed by the ground and vegetation are then re-emitted as thermal (longwave) energy, and rapidly accelerating snowmelt around their perimeter.

Loveland Pass on June 1.  Slight dust present but not visible in photo.

HOOSIER PASS:

Hoosier Pass snow profile.  Dust event D4 was noted at this CODOS site on April 15.  Since then, with Loveland and Berthoud Pass having received dust from event D5, it was very likely deposited in this location as well, combining with D4.   

Photo of Hoosier Pass CODOS sample area.  The cleaner blocks from the snow pit can be seen in the foreground.  

Photo taken from Hoosier Pass CODOS site looking at Mt. Bross.  Similar to Berthoud and Loveland Pass, dust deposition in this area is light.  Further to the southwest the Collegiate Peaks received a greater amount of dust deposition.

 

PRECIPITATION AND STREAM DISCHARGE

 

Looking at spring precipitation (see Mar/Apr/May Precip Variance plot below), the Central and Southern Mountains recovered pretty well from a dry February and March.  All major watersheds experienced a series of storm events since mid-April that resulted in further snowpack development.  Many SNOTEL sites, particularly in the Southern Mountains, were exhibiting deficits on May 15 that since have largely recovered by June 1.  The Northern Mountains, with the exception of Grizzly Peak, have seen spring precipitation on average 25% above the long term mean. The overall average variance for the 15 stations is 3% above the long term mean, with a maximum range between stations of 51%.  

Current cumulative precipitation for WY2016 at Senator Beck is the third highest, albeit not by much, in our 13 year record.  Yet, WY2016 is ranked only ninth highest in cumulative winter storm count (see plots below).  One explanation is we have received a number of storms this winter season that barely fell short of our definition of a storm, requiring at least 12 mm of precipitation with no gap in precipitation greater than 12 hours.  Also, on at least one occasion we received multiple storm systems with no gap in precipitation, making it difficult to designate precipitation totals for each storm. 

Combined March, April, and May precipitation, through June 1, 2016.   On May 15, 2016, precipitation had fallen short of average for ten of these fifteen SNOTEL stations adjacent to or near CODOS monitoring sites.  Since May 15, all stations recorded improved cumulative totals, with average change in percent deviation from the mean increasing 12%. Overall, the average variance for the 15 stations is 3% above the long term mean. 

Cumulative precipitation as of June 1, 2016.  WY2016, so far, is the third highest (barely) in our 13 year record.

Cumulative winter storm count for 13 years at Senator Beck Basin.  WY2016 is currently ranked ninth in the number of documented winter storms.

These final precipitation data will change the CODOS Dust Enhanced Runoff Classification (DERC) for a number of hydrographs.  Within the DERC model, there are many instances where WY2016 classification does not have a previous water year equivalent.  Nonetheless, the next best prior water year(s) may provide useful insights into the remainder of the spring 2016 snowmelt runoff cycle (see CODOS site webpages for updated hydrographs and for the complete DERC hydrograph database for these watersheds).  An updated chart is provided below.  Items highlighted in bold indicate there was no prior water year that fits the current WY2016 scenario for that particular watershed:

May 31 CODOS Update: D2-D6 Merged at SASP

May 31 CODOS Update: D2-D6 Merged at SASP

Greetings from Silverton,

Together, with the emergence of D5/D6 as reported in the May 22 Update, along with the subsequent sunny and warm weather that followed, the snowpack at SASP has quickly melted to where dust layers D2-D6 are now merged at the surface.