CODOS Update March 25, 2020: Second Leg of March CODOS Tour

We conducted the second leg of the March CODOS Tour from March 19-21, the usual weekly snow profile at Swamp Angel Study Plot March 23, and also visited Senator Beck Study Plot on March 24. As expected, based on our findings from the first leg of the March CODOS Tour, we did not observe any noticeable dust at any of the sites except Wolf Creek. The Wolf Creek dust layer is consistent with the dust layer at Swampy being about 3’ below the surface. The Wolf Creek dust layer however is a good bit dirtier than observed at Swampy (see pictures below). Fortunately we did not observe dust higher up in the Rio Grande Basin at the Spring Creek site, indicating that dust mostly stayed in the Southern portion of the San Juan Mountains.

Being about a month into the dust-on-snow season the snowpack going by our +/-15% of median criteria is considered “average” across Colorado. And dust conditions thus far this spring is falling under “minimum dust” for all sites. Current conditions and future changing conditions will inform what we might expect to see in terms of streamflow under the Dust Enhanced Runoff Classification that we posted in our March 1 report. Dust conditions can turn just after one storm, particularly if a nasty dust event is deposited on the surface near peak snow accumulation. The CODOS team will do another statewide tour mid-April then again mid-May and like always continuous monitoring in Senator Beck Study Basin.

Over the last 7 days Swamp Angel at Red Mt Pass received 2” of precipitation. The Southern Basins really needed this productive storm(s) to shore up the snowpack as we get closer and closer to peak accumulation time-frame. Northern Basins are faring a bit better with the snowpack already sitting near their respective median peak SWE. The NWS calls for another chance of snow accumulation mainly Thursday thru Friday and this system looks to favor the Northern Mountains. A ridge moves in over the weekend but then another trough might arrive early next week as the Pacific Northwest storm track we have been seeing remains active.

SNOWPACK CONDITIONS

Swamp Angel Study Plot (March 23): Dust event #1 (D1), a moderate diffuse dust layer observed at 3.4’ (3’ below snow surface), this is the only observed dust layer thus far this season. Snow depth = 6.4’. SWE= 23.4”.

Senator Beck Study Plot (March 24): SBSP is at elevation 12,200’. Snow depth = 6.1’. SWE = 23.2”. Inconclusive evidence of D1, possibly due to extensive wind transport during the initial storm that brought the dust and subsequent storms. It is possible D1 might exist a couple feet below the surface at an old surface layer.

Grand Mesa (March 19): We did not do a snow profile at the usual location due to inclement weather closing the access road. We did do a hasty pit at a representative location on Grand Mesa. No obvious dust observed. If there is light dust present it is ~2’ below surface where we observed an accumulation of local debris underneath a melt/freeze crust.

Park Cone (March 19): No dust visible in snowpack. Evidence of heavy snowmobile traffic in NRCS snow course and CODOS study plot. Snow depth = 3.4’. SWE = 9.3”.

Spring Creek (March 20): No obvious dust observed. Signs of heavy snowmobile traffic in study area. Snow depth = 3.6’. SWE = 11.8”.

Wolf Creek (March 20): Very dusty layer 2.8’ below snow surface. Snow depth = 6.5’. SWE = 24.7”.

Rabbit Ears Pass (March 21): No dust observed. Snow depth = 6.9’. SWE = 28.4”.

Willow Creek Pass (March 21): No dust observed. Snow depth = 3.4’. SWE = 10.8”.