March 27, 2016: CODOS Update –  

SUMMARY 

The timing of our Colorado Dust-on-Snow (CODOS) fieldwork has been tricky with attempts to work around multiple storm systems, but during a complete circuit of all eleven CODOS program monitoring sites, from March 19-23, 2016, we documented a complete absence of dust-on-snow at the north and northeast monitoring locations, and dust within and/or on the surface of the snow at the remaining central and southern locations.  However, on Tuesday, March 22, dust event #3 for WY2016 (D3) occurred during the latter portion of the trip, so it is possible these sites that were dust free prior to March 22, now have dust (as well as the other sites) near the surface of the snowpack.  The morning after D3 occurred the CODOS team visited Wolf Creek Pass, Spring Creek Pass, and our Swamp Angel study plot and documented the severity of the event, findings are discussed below.  Since March 1st, snow water equivalent (SWE) information from SNOTEL sites that we originally characterized as low or average in the Southern Basins has largely deteriorated, and we have also recorded isothermal or near isothermal snowpack temperatures at a couple CODOS locations.  SNOTEL data indicate Northern Basins have seen an overall increase in SWE, based on percentage of median values. Current near-term weather products indicate a slight reduced precipitation probability compared to the mid-February forecast, likely since we are approaching summer and a transition to ENSO-neutral is likely during late Northern Hemisphere spring or early summer.  Temperature probability forecasts have also evolved from normal/below normal to above normal over this same period.   Still, the prediction of a greater chance of precipitation than normal suggest there remains the possibility of maintaining, or improving snowpack conditions close to median Peak SWE in most Colorado watersheds.  WY2016 March 1st SWE conditions ranged from “Low” to “High” on the Dust Enhanced Runoff Classification (DERC) model and are now trending, as of late March, “Dry” to “Avg” for spring precipitation conditions within that March 1st SWE domain.  This being an active period for dust-on-snow events, it is still too early to characterize dust conditions as being either “Min”, “Avg”, or “Max” for the winter season.     

DUST CONDITIONS 

We are now nearly a month into the March/April/May dust-on-snow season with a total of three dust-on-snow events having been observed so far at the Senator Beck Basin site at Red Mountain Pass, and dust was observed at half of our other ten CODOS sites during the March 19-23, 2016 circuit. Typically the San Juan Mountains receive 8-9 dust-on-snow events a winter, based on observations going back to 2005.  Storm opportunities are also dust opportunities, and the Senator Beck sentry site is starting to fall behind on storm counts (defined as greater than 12 mm of precipitation with no break in precipitation greater than 12 hours).   By this point in the season the average storm events having occurred is 19 (see graph below). That said, after the storm on March 23 we are now at Storm #16, and as of this writing Saturday morning, March 26, we are now receiving Storm #17.  Five of the now 17 storms have occurred in the last 2-months.  Near-term forecasts call for a greater than average chance of precipitation (see forecast discussion below) and this implies, coupled with the necessary soil, weather, and wind conditions, an increased chance of more dust-on-snow events for Colorado from SW’ly wind fields over the Southern Colorado Plateau.   

CODOS Dust Alert: D3

Greetings from Silverton,

On Tuesday, March 22, dust event #3 (D3) began in the afternoon in the San Juan Mountain region.  Then (at Senator Beck Study Basin), starting approximately 8 pm that evening, snowfall started covering the newly deposited dust with 13" (33 cm) of clean snow by the following evening. 

The ridge that was sitting over much of the West that had us pinned down, making us suffer a mostly dry and warm February, has finely moved on.  Yesterday and last night a passing, wet storm has deposited approximately 1' of new snow at Swamp Angel Study Plot. The next system will be near the California/ Mexico border tonight and may bring minor snow accumulations Tuesday and Wednesday.  Other storms are sitting over the western and central Pacific Ocean, so it seems that we have a basic Spring pattern in place, and, while the strength of the El Nino is predicted to decrease in boreal spring, it is probable (according to NWS) that El Nino conditions will remain strong most of March....We'll see.  

SUMMARY

Colorado has begun March with average conditions dominating the range of snowpack conditions among the major basins across the Colorado mountain system.  This Update 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.  This Update summarizes the state by Basin, and provides a site-specific analyses for each CODOS site (linked below). 

Many of you who live on the Western Slope and experienced the high wind event yesterday and last night likely anticipated this e-mail, but dust season has resumed at Senator Beck Basin.  At Swamp Angel Study Plot this (Friday, February 19) morning, a very noticeable new dust layer D2-WY 2016 was deposited ‘wet’, overnight last night, along with 2 mm of precipitation.  
 

CODOS Update – January 25, 2016 

Greetings from Silverton, 

We hope you have been able to go outside and enjoy the snow.   

As of this date, we have observed only a single dust-on-snow event here at our Senator Beck Basin Study Area, D1-WY2016 event on December 11-12, 2015. This event deposited 0.0748 g/m² of dust with the two day storm and was immediately buried.  As of right now the D1 layer is buried deep in the approximate 1.6 m (5.3’) snowpack, just above the ground and will have comparatively minor impacts on next spring’s snowmelt runoff cycle, as the last layer to merge with the overlying layers during the snowcover ablation process.  This dust event is the 5th dust-on-snow event occurring during the month of December documented since 2005.

Andrew Temple and I (Chris Landry) collected a sample of the first discernible dust-on-snow event of the season (D1-WY 2016) today at the Senator Beck Basin Swamp Angel Study Plot at Red Mountain Pass.  This moderately heavy event was deposited during the early hours of Winter Storm #6 on December 11-12.  Given the dust layer's location near the base of the snowpack, D1-WY2016 will have comparatively minor impacts on next spring's snowmelt runoff cycle, as the last layer to merge with the overlying layers during the snowcover ablation process.

Although not common, CSAS has logged a number of December dust-on-snow events since WY2005 - this is the fifth such December event.  The photo attached shows the layer some 16" below the snowpack surface at the Swamp Angel Study Plot.

SUMMARY

Through a highly unusual combination of weather events including hurricanes on both ends of the winter, a “ridiculously resilient ridge” to the west yielding two mid-winter droughts and scant Winter Storms until a “Miracle May”, and atypical snowpack conditions including early onset of melt with almost no dust-on-snow in the snowpack, the Colorado Mountains eventually produced full reservoirs and streams, ‘on time’.   This Colorado Dust-on-Snow program WY 2015 Season Summary will discuss the ‘weirding’ of Colorado’s winter at the Senator Beck Basin Study Area at Red Mountain Pass and at ten other sites located throughout the Colorado Mountains.

SUMMARY

Final CODOS visits were conducted at Hoosier, Loveland, Berthoud, Willow Creek, Rabbit Ears, and McClure Pass sites on June 16 and 17, and Independence Pass was also visited on June 15.  Merged but comparatively weak dust-on-snow was observed at the snowpack surface in all locales, producing an incremental but still meaningful reduction in snow albedo and absorbing solar radiation, but other sources of energy had driven the snowmelt energy budget until recently.  Dust samples were collected at Independence, Loveland, and Berthoud Pass sites.    Very high streamflows were observed in these watersheds.   A discussion of the pattern and high amplitude of recent statewide snowmelt behavior is presented. 

DUST-ON-SNOW CONDITIONS

As CODOS program participants know, no additional dust-on-snow events were observed by CODOS at the Senator Beck Basin (SBB) sentry site since the D3-WY2015 event of April 14/15 (see Dust Log).  The total WY 2015 mass of mineral dust deposited to-date at the Swamp Angel Study Plot in SBB, from events D1 (April 2), D2 (April 8) and D3 (April 14/15), is 2.048 grams per square meter (2 g/m2), a small fraction of the dust depositions observed in prior seasons (see Mass Loading Data).  As such, WY 2015 dust intensity at SBB and throughout the state ranked as comparatively minimal (i.e., MIN Dust) within the CODOS period of record and within the Dust Enhanced Runoff Classification scheme.

During this CODOS circuit, dust event layers D3, and perhaps D2 and D1 (where present) were observed merged in a single layer at the snowpack surface on all aspects and at all elevations.  Viewed from a distance, most remaining snowcover appeared ‘clean’, although not as clean as seen during May, when new snow repeatedly restored very high snow albedo throughout the Colorado mountains.   However, closer inspection revealed that this merged dust at the surface was darkening the snow surface and producing a comparatively minor reduction in albedo.  While not as dramatic as in prior years, this incremental reduction in albedo was enhancing the radiative forcing of snowmelt, adding additional absorbed solar energy to the snowmelt energy budget.

“All layers merged” (ALM) samples of this dust were collected at Independence Pass, near the summit of Loveland Pass, and at the Berthoud Summit CODOS site (see photos below).  These ALM samples were sent to our USGS collaborators for chemical and other analyses, for inter-site comparison.   ALM samples were not collected at Hoosier Pass, Willow Creek Pass, Rabbit Ears Pass, and McClure Pass due to lack of snow at or near the CODOS site.  

SUMMARY

Site visits and dust sample collection were conducted at Senator Beck Basin, Grand Mesa, upper Gunnison Basin, Spring Creek Pass, and Wolf Creek Pass sites on June 1 and 2.  Snowpack conditions experienced a major turnaround in late May thanks to heavy and even record precipitation.   Under clear and sunny skies, May snow was rapidly melting even though  a comparatively weak merged dust layer was only beginning to emerge at the surface of the lowest elevations of remaining snowcover.   Dust emergence continues as of this writing.  Streamflows were surging by early June to high levels not well predicted by previously identified ‘best fit’ WY 2012 and 2007 hydrograph patterns.   Wet weather is returning and could result in further surging in streamflows from the combined effects of heavy rain below snowline and heavy rain-on-snow beginning Thursday, June 5 and over the following weekend.  Forecasts continue to anticipate a wetter than normal June, July, and August.

DUST-ON-SNOW CONDITIONS

No new dust-on-snow events were observed by CODOS at the Senator Beck Basin (SBB) sentry site since the D3-WY2015 event of April 14/15 (see Dust Log).  The total WY 2015 mass of mineral dust deposited to-date at the Swamp Angel Study Plot in SBB, from events D1 (April 2), D2 (April 8) and D3 (April 14/15), is 2.048 grams per square meter (2 g/m2), a small fraction of the dust depositions observed by in prior seasons (see Mass Loading Data).  June dust-on-snow events are comparatively rare.

During this partial CODOS circuit, a (merged) dust layer containing dust events D3 and perhaps D2 and D1 was on the verge of emerging, or had emerged, at the snowpack surface at Swamp Angel Study Plot, on Grand Mesa, at Kebler Pass near Crested Butte, and on Wolf Creek Pass, and on nearby high elevation terrain at Spring Creek Pass.  Snow albedo was visibly but not dramatically reduced by this dust emergence.  Samples of this “all layers merged” dust were collected (except at Spring Creek Pass) for chemical and other analyses by our USGS collaborators (photos below). 

MAY 18, 2015 UPDATE – STORMY MAY PROLONGING AND ENHANCING RUNOFF

SUMMARY

Despite sub-par March/April/May total precipitation to-date over almost all CODOS sites, the month of May 2015 has been notably wet and stormy, as correctly anticipated by the NOAA Climate Prediction Center.  With no additional dust-on-snow  since event D3 (April 14/15), and frequent snowfalls since then, the minimal dust contained in the Colorado snowpack has remained generally well-buried under clean snow, and snow albedo levels have remained high.  WY 2015 snowmelt runoff hydrographs have most closely resembled either spring 2007 or spring 2012 Dust Enhanced Runoff Classification patterns, to-date, despite some new behaviors and unusual conditions.  This Update is supplemented by updated snowpack SWE plots and hydrographs posted to the specific webpages for these CODOS sites.  (CODOS site webpage links are shown at the top of the CODOS Program home page, and on all site pages).

Dust emerging in San Juan Mountains

Compared to mountains farther north and east of us, the San Juan Mountains have seen substantially less snowfall since the D3 event of April 14/15.  That thinner layer of new and clean snow, from our Storms #13 and #12, is now melting rapidly and revealing our merged dust layers D3/D2/D1 on east-, south-, and west-facing slopes where D3 fell onto existing snowcover, and on 'flat' terrain.  As is typically the case, the highest, north-facing terrain currently retains the most recent new snow and correspondingly higher snow albedo.  Otherwise, snow albedo is currently declining here in the San Juan Mountains, albeit relatively subtly, producing corresponding upticks in snowmelt rates and streamflows following a period of declining or 'flat' flow levels.  

APRIL 27, 2015 UPDATE – CENTRAL & NORTHERN MOUNTAINS, FRONT RANGE

SUMMARY

CODOS sites at McClure Pass, Rabbit Ears Pass, Willow Creek Pass, Berthoud Pass, Loveland Pass, Hoosier Pass, and the Park Cone site in Taylor Park were visited over April 20-22, 2015.  Dust layer D3 (April 14/15), merged with layer D2 (April 8), was clearly evident in the Central Mountain sites (McClure Pass and Park Cone) underneath the recent new layer of clean snow (CSAS Storm #12) and dust intensity in those locales could attain “AVG Dust” with just a few additional events.  D3 was weaker at Northern Mountain sites (Rabbit Ears Pass and Willow Creek Pass) and at Berthoud Pass, and very faint, even ambiguously present, in our other Front Range locales (Grizzly Peak and Hoosier Pass).   Dust intensity remains in the “MIN Dust” classification in those areas.  Dust was not apparent at the snowpack surface in any of these locales, during this circuit, and where dust was present it was well-buried under 4-15” of clean snow containing from 0.5” to 3.2” of water equivalent.  Snowpack temperatures were near 0 C in the lower snowcover and cooler near the surface, a typical temperature profile pattern for late April at these sites.  This Update presents text and photographs to complement the new snow profiles, snowpack SWE plots, and hydrographs posted to the specific webpages for these CODOS sites (all CODOS site webpage links are shown at the top of the CODOS Program home page , and on all site pages).

McCLURE PASS – APRIL 20

Spring was well underway at McClure Pass and snowcover at the CODOS site and at the adjacent McClure Pass Snotel had completely disappeared prior to the recent winter storm (CSAS Storm #12).  Only post-D3 new snow covered the ground at that site so an alternative snowpit site was selected on a nearby north-facing slope where old snow remained, enabling the verification of presence/absence of dust layers.

APRIL 20 UPDATE – SAN JUAN MOUNTAINS, GRAND MESA

SUMMARY

Dust-on-snow event D3-WY2015 was verified at our Swamp Angel Study Plot on April 15 (as reported in our Dust Alert that day) and during a just-completed circuit of the CODOS sites at Grand Mesa, Spring Creek Pass, and Wolf Creek Pass on April 16 and 17.  Dust layer D3 was observed at all of those sites in varying strengths, already merged with layers D2 and/or D1 where those layers had been deposited.   Although snowpack temperatures had cooled in near-surface layers, temporarily disrupting snowmelt discharge, those snowpacks also remained very warm overall.   As of the date of the site visits, anywhere from a trace to 4” of clean new snow overlay the D3/D2/D1 dust layer; subsequent snowfall may have resulted in deeper burial of the dust layer on Grand Mesa.   Dust layer D3 is substantial enough to eventually result in significant reductions in snow albedo, once re-exposed to direct solar radiation.  The merged D3/D2/D1 dust intensity currently remains within the “MIN Dust” domain of the Dust Enhanced Runoff Classification rankings at these sites although one or two additional dust-on-snow events could increase conditions to “AVG Dust”.  This Update presents text and photographs to complement the new snow profiles, snowpack SWE plots, and hydrographs posted to the specific webpages for these CODOS sites (all CODOS site webpage links are shown at the top of the CODOS Program home page , and on all site pages).

CODOS Dust Alert - Event D3 of WY 2015

Our third dust-on-snow event of WY 2015 did pan out, as was speculated upon yesterday, with the heaviest deposition of the season at Senator Beck Basin.  Timing of this event was a bit slower than anticipated.  Somewhat surprisingly, visibility from Silverton was still virtually undiminished at around 6 PM on Wednesday, April 14, even under strong SW’ly winds. 

CODOS Dust Alert – Potential High for Event D3 of WY 2015

As has been very well advertised by the National Weather Service, a potent, synoptic-scale weather system is approaching western Colorado this afternoon with a strong, pre-frontal wind field developing over the Colorado Plateau.  A High Wind Warning has been issued for strong SW’ly winds (SSW to WSW) and blowing dust is in the forecast this afternoon and this evening at several locales throughout the Plateau, from Leupp, AZ to Moab, UT.  As of 1:16 PM this afternoon airborne dust was beginning to obscure visibility from the USGS Abajo Peak

CODOS Dust Alert - Event D2 of WY 2015

Wednesday, April 8, produced another very weak dust-on-snow event here in Silverton, the second event (D2) of WY 2015.  Strong winds from the SSW and SW were underway at dawn on Wednesday but, as is often the case, dust only became apparent in the air, as reduced visibility, around mid-day.  Farther to the southwest, the USGS webcam at Abajo Peak, in Utah, showed substantial dust in the air by mid-morning, fully obscuring the view of Sleeping Ute Mountain, 55 miles to the southeast of Abajo Peak. 

SUMMARY

March 2015 began with a significant winter storm but continued and ended with very scant subsequent precipitation over most of the Colorado mountain system.  Consequently, during March, snowpacks saw either no net gain or declined, some quite substantially.  March also produced no dust-on-snow deposition events for Colorado, the result of either an absence of sufficient winds over the Colorado Plateau when soils were available in mid- and late-March, or the unavailability of loose soil during the strong winds associated with the major winter storm at the beginning of March.  Colorado entered April with the first dust-on-snow event of the season, warm and significantly sub-par snowpacks, snowmelt underway, and predictions of continued drought conditions for much of the mountain system and for the Colorado Plateau.  

CODOS Dust Alert - Event D1 - WY 2015

Greetings from Silverton -

Following an unusually dust-free March, an almost inevitable combination of strong SW'ly and W'ly winds and dry soil conditions finally occurred over the Colorado Plateau and generated our first dust-on-snow event of Water Year 2015 here in the western San Juan Mountains, and in Senator Beck Basin.  This event began lateWednesday afternoon and evening, April 1st, at low intensity and was perhaps more intense overnight before fading somewhat to a visible haze at dawn on Thursday morning, April 2nd, under still moderate SW'ly winds.  Winds then re-intensified during the day Thursday and began a swing to the WSW, W, and eventually NW by evening, as visibility was restored to 'crystal clear' sky conditions by sunset.  Strong winds and dust were observed in the Grand Valley, in Durango, in Gunnison, and elsewhere on the West Slope on both Wednesday and Thursday. 

March 23, 2015: CODOS Update – Dust-Free Snowmelt Underway

SUMMARY

During a complete circuit of all eleven Colorado Dust-on-Snow (CODOS) program monitoring sites, from March 17-20, 2015, we documented a complete absence of dust-on-snow in the Colorado mountains to-date, unusual spatial variation in snowpack conditions, and early isothermal snowpack temperatures generating snowmelt runoff at high streamflow levels for late March.  Current near-term weather forecast products suggest continued dry weather well into April and very low chances of achieving median Peak SWE conditions in most Colorado watersheds.  WY 2015 snowmelt season conditions began on March 1 within either the “Avg” or “Low” March 1 SWE condition domains of the DERC model and are trending, as of late March, toward “Min Dust” and “Avg” or “Dry” Spring precipitation conditions within that March 1 SWE domain.