CODOS Update March 18, 2022: CODOS Tour - The Good, the Bad, and the Ugly — Colorado Dust-on-Snow Program (original) (raw)

Greetings from Silverton,

A theme quickly emerged this week while digging snow profiles on the CODOS statewide tour. There are two buried old surface crusts throughout the state’s snowpack and above and below these crusts is snow of very poor structure (see CAIC). When stepping off your skis to dig a profile you sink into the snow at least to your waist. Upon these two crusts lie the dust, if it was deposited, from the last two dust-on-snow events (D2 and D3). These dust events that ushered in productive storms were promptly buried by the ensuing snowfall on February 21 (D2) and March 4 (D3).

The Good: The dust laden storms that struck the snowpack so far this year have originated out of the Southwest and didn’t have the energy (dust load, storm track, etc) to carry the dust to Northern Colorado. We did not observe dust in the snow at locations approximately north of the latitude of Hoosier Pass. At Hoosier there is very noticeable light dust and at Loveland Pass that layer is not noticeable. The delineating latitude is approximate because there are reports of a stark dust layer from event D2 in Eagle County. We noted a distinct dust layer at McClure Pass and it is likely dust was carried directly north a bit farther before dropping out. We did not observe dust at Rabbit Ears, Loveland Pass, Berthoud Pass, or Willow Creek Pass. So far this season northern basins have a clean snowpack and near normal SWE and currently fall into the “good” category.

The Bad: I don’t want to be judgy, how about “misguided”. The GunnisonBasin and northmost San Juan Mountains received a good dose from D2/D3 before the events dissipated traveling northward. The severity is not light by any means, but as of now appears to fall squarely in the moderate category. At Park Cone, McClure, and Spring Creek, which are typically a more shallow snowpack, D2/3 are not very far under the surface, about 2” SWE covers both layers (see table below). Elsewhere with deeper snowpack it is a good bit farther down due to greater snow accumulation. In terms of SWE at the CODOS sample sites, which are located in slightly different locations than the nearby SNOTELS, the above sites seem to have more snow for this time of year than in recent past, although looking at the SNOTEL data it is a mixed bag (see SNOTEL plots at bottom of page).

Senator Beck Study Basin (SBB), which includes Swamp Angel, is on the cusp but for now will fall into this general category of moderate conditions (although that can easily change with just one more DOS event). SBB is located at the headwaters of the Uncompahgre, San Miguel, Dolores, and Animas watersheds. Dust conditions worsen the farther down these watersheds you travel.

The Ugly: Beauty is in the eye of the beholder, but if a dust free snowpack is considered ideal then areas of Colorado that are struggling are the Rio Grande, San Miguel, Dolores, and Animas. It is pretty remarkable the difference in dust severity going from Molas Pass over to Red Mt Pass. At Molas, all three dust layers are pretty bad and really jump out at you. At Senator Beck Study Basin (Red Mt Pass), D1 is extremely faint and D2/3 appears in middle/upper class of moderate severity. Before April the CODOS team intends to dig profiles further down the southern watersheds to assess in further detail this dust severity gradient. For the Rio Grande Basin, read the summary below, it is in a class of it’s very own.

Since joining Center for Snow & Avalanche Studies I have yet to place a region in the category of “maximum dust conditions” of the three general categories of “minimum”, “average”, and “maximum”. I have come close with some areas categorized as “upper end of average”, but we have yet to see the dust severity (either as one severe event or cumulative events) that we saw during the “maximum” years of the past. It appears this season the basins mentioned in this category will fall under “max’ dust. In the Dolores, for example, it stems from three equally bad dust layers (see pics below). In the Rio Grande it is warranted based on the severity of D2 in that region (again please see pics).

We have at least a couple weeks left of the accumulation season and hopefully it will include more snow sans dust. March/April/May is when we receive the most dust-on-snow events. Any more dust deposition will exacerbate current conditions particularly in Central/Southern Colorado. How the existing dust will affect snowmelt timing and rates will depend on spring weather. If we have a wet spring with regular storm events that keep adding to the snowpack and keep dust layers temporarily buried, the dust will be less of a factor as these “albedo resets” will slow snowmelt. This scenario is unlikely as the forecast for the next few months is dry and warm. And, the worst of the dust is located in the uppermost portion of the snowpack, 2”-6” SWE currently cover the dust in the central/southern mountains. Once exposed it will greatly darken the snow surface unless covered by regular snowfall.

A summary for each CODOS site is below. If you want more details, please see snow profile forms here. And feel free to email or call the CSAS office with questions.

Off topic, you likely heard about the big Sahara dust storm, if not see this Washington Post article.

SWAMP ANGEL (Red Mt Pass): March 11

On March 11 we measured 18.7” SWE as 74.4” snow depth at Swamp Angel. Nearby Red Mt SNOTEL reports essentially the same. There was 2.2” SWE over D3 and 5.5” over D2. D1, which occurred on December 26, is farther down the snowpack and is very faint at SBB but much more severe in other areas of the southwest mountains.

The first photo below was taken by Chris Bilbrey with CAIC on March 4 in the Columbus Basin. Three separate dust layers came out of the Feb storm cycle in this area - this is the only area where this has been observed - where we observed just the one layer elsewhere. This is much more severe than at SBB, and that is not counting D1 which is bad in La Plata, Dolores, San Miguel, etc.