Observation: Snake Creek

Observation Date
12/12/2020
Observer Name
B
Region
Salt Lake » Big Cottonwood Canyon » Brighton Perimeter » Snake Creek
Location Name or Route
Snake Creek Canyon
Weather
Sky
Overcast
Precipitation
Light Snowfall
Wind Direction
Northwest
Wind Speed
Moderate
Weather Comments
Most of the morning and afternoon saw overcast skies with intermittent snow squalls with accumulations during the day around 7 cm. Winds were sustained in the Moderate category on the ridge lines and not getting down in the drainages. Wind Blown and or Transport was Light on the ridges, but definitely creating Soft Wind Slabs, and sculpting in exposed terrain. Temperatures remained in the single digits throughout the day.
Snow Characteristics
New Snow Depth
7"
New Snow Density
Low
Snow Surface Conditions
Powder
Faceted Loose
Wind Crust
Melt-Freeze Crust
Snow Characteristics Comments
The day started out with 7 inches of new snow from over the last 18 hours. Still a mixed bag out there with much of the Southerly facing terrain void of snow before this event. Minor aspect adjustments to get slightly off due South when combined with Low Slope Angles allowed for moderately safe riding on SSE and ESE aspects. On these aspects there was a thin hard m/f crust that allowed you to keep off the ground, and hopefully away from any buried obsticals. Definitely the best riding was on Low Angle Slopes when on the Lower Half of the compass. The off aspects and those on the upper half of the compass had a bottomless feeling. Yet the critical component was finding terrain that didn't have old pre-storm tracks.
Red Flags
Red Flags
Recent Avalanches
Heavy Snowfall
Wind Loading
Cracking
Poor Snowpack Structure
Red Flags Comments
The poor snowpack structure that has been developing is now buried and in places that had any Wind Loading it was easy to initiate Cracking. In these locations the Collapsing appeared to be occurring directly below the Ambient Crust Layer that was the surface snow before todays event. Of Note: during one period when there was minimally adequate visibility it was possible to see recent/new debris that had appeared to release from the V Tree area. Unfortunately this period of visibility was short and poor, so no photos available. Most likely there had been a Natural Release as a result of Cross Loading in the steeper areas of the Chute/Cliffs. Size appeared to be D1.5.
Avalanche Problem #1
Problem
Wind Drifted Snow
Trend
Increasing Danger
Problem #1 Comments
At this point in time Wind Slab as described above appears to the most likely Avalanche Problem/Issue, and it is probably still increasing in trend in the Upper Elevation/Ridgeline Terrain.
Avalanche Problem #2
Problem
Persistent Weak Layer
Trend
Increasing Danger
Problem #2 Comments
As the depth and load from the new snow increases, the Poor Snowpack Structure that is Widespread will come more into play. During the morning hours it appeared that the New Snow did not have enough weight to overload the fragile pre-existing snowpack in sheltered terrain. Yet as stated above, in any areas where the Winds had minimally aided in increasing the new load, the PWL's were very sensitive. When the 7 inches of new snow changed to 14 inches of soft slab from cross and upslope loading the weak layers were reactive. Of Note, it was also easy to initiate Cracking on 30 to 33 degree slopes; and Hasty Pits and Hand Shears easily initiated clean shears at the interface of the New Snow and the pre-storm NSF's. Also of concern are the variety of PWL's that can be found out there. Crust Facet Sandwiches on SSE, ESE, SSW and WSW are just a few of the areas that are housing unusually weak snow; and of course E, N and W aspects have typical weak structure for this time of the year.
It appeared that the Danger today was Moderate and with any continued precip and or winds the Danger for Sunday may rise to Considerable experiencing any kind of increasing loads. With this in mind, at some point, Remote Triggering from a distance may be a real concern.
Today's Observed Danger Rating
Moderate
Tomorrows Estimated Danger Rating
Considerable
Coordinates