Pro Field Report
Basic Information
Observation Details
Observation Date:
December 27, 2021Submitted:
December 28, 2021Observer:
SAC - VandenBos, WielandZone or Region:
Galena Summit and Eastern MtnsLocation:
Baker Creek (6,700-9,200', E-NE-N-NW)Signs of Unstable Snow
Recent Avalanches?
YesCracking?
IsolatedCollapsing?
None ExperiencedSnow Stability
Stability Rating:
FairConfidence in Rating:
LowStability Trend:
SteadyMedia/Attachments
Advanced Information
Weather Summary
Cloud Cover:
OvercastTemperature:
estimated in single digits FWind:
Moderate , NWCalm to light winds increasing to moderate and switching to W/NW with frontal passage in the afternoon. Snowfall started at this same, S-1 to S1 with 1-2cm of accumulation by the end of the day.
Avalanche Observations
We observed several D2 avalanches at upper and middle elevations that had failed within the past day or two. Our visibility was poor and we could not see very much terrain.
Snowpack Observations
My main curiosities for the day were: the presence of weak layers in the upper snowpack, depth of snowpack and stiffness of slab overlying 12/11 weak layer, and pattern of natural activity. The snowpack where we traveled was a bit shallower than what I had observed at the south of Baker Creek the day before (~150cm vs ~180cm). Both of our two big storm events dropped a bit more snow at the mouth of Baker Creek. The slab that I observed today was ~100cm thick with 30-40cm of F- snow at the top, then grading from 4F to 1F+/P- at the base. The weak layer here is well developed and is not visually showing signs of healing, yet. On a N-facing slope at 8,100', this slab produced ECTP 26 and 31, and CPST 38/100 and 33/100 both to END.
There is a very subtle layer in the upper snowpack that exists within the storm snow from the previous 5 days. In this location it is 30cm down, at the mouth of Baker it is 50cm down. Reports from Lake Creek indicate a similar layer about 50cm down. In my pits on Butterfield and Baker this layer is poorly defined and did not produce unstable snowpack test results, but did produce rough breaks in ECTs in the low teens and was apparent in shovel shear. I couldn't make out a specific grain, my guess is that this could be either a product of the lull on Christmas Eve (seems a bit shallow for that) or some variety of crystal change that occurred with the passage of one of the fronts a bit later in the storm. Worth monitoring.
Winds picked up in the afternoon and were drifting snow at upper elevations. We observed extensive cracking along the backside of a cornice on an upper elevation ridge, with cracks extending at least 100m and opening up to 15 cm wide.
Avalanche Problems
| Problem | Location | Distribution | Sensitivity | Size | Comments |
|---|---|---|---|---|---|
Deep Persistent Slab
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Weak Layer(s):
Dec 11, 2021 (FC)
Comments: Rose shaded based on this and previous obs on this layer. Have been feeling comfortable thinking of this as a deep persistent problem for a bit now, am starting to feel comfortable describing it that way in fx. |
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Wind Slab
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Terrain Use
Continuing to avoid avalanche terrain where 12/11 exists.