Sawtooth Avalanche Center

Pro Field Report

Basic Information

Observation Details

Observation Date:
December 7, 2021
Submitted:
December 9, 2021
Observer:
SAC - VandenBos (off duty)
Zone or Region:
Galena Summit and Eastern Mtns
Location:
North Fork Big Wood (6,250-11,200', all aspects)

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
None Experienced
Collapsing? 
None Experienced

Snow Stability

Stability Rating: 
Very Good
Confidence in Rating: 
Moderate
Stability Trend: 
Steady

Advanced Information

Weather Summary

Cloud Cover:
Clear
Wind:
Moderate , NW
New/Recent Snowfall:
trace

Beautiful blue and cold day. Didn't feel like ambient temperatures climbed above ~30 F at upper elevations. Steady NW winds blowing at upper elevations, restricted to ridgelines.

Avalanche Observations

None observed, beyond D1 wet loose dribbles from previous warm weather.

Snowpack Observations

Snowpack in this area seems to be tracking pretty well with other snowpacks I've observed in the region this season. Solar aspects have been completely burned off, often up to at least 9,000'. Where snow exists on these aspects it is pretty thoroughly cooked, with multiple thick, icy, crusty layers dominating the snowpack. Surfaces on solars are very icy, many are presenting as variably thick water-ice crusts. The major wind event on 12/5-6 was able to rip up some of these crusts (often exposing older crusts below). This wind produced a significantly more variable snow surface at upper elevations and in quite a bit of middle elevation terrain as well. I suspect this will help mute the sensitivity of the surface at upper elevations on the average, but will probably make it harder to assess individual slope stability.
As you wrap away from sunny aspects and toward the northern half of the compass the snowpack becomes increasingly concerning. On shaded slopes there are several sets of crusts in the upper snowpack interspersed by layers of facets. The worst faceting is occurring below the surface crusts, but in most areas the entire pack seems to be in a faceting regime. The cold weather isn't helping. The lack of a slab on top of this weak snow makes it hard to assess how it will behave as it gets loaded, but I'd imagine we will see a fair bit of avalanche activity if we throw a big punch of water at this snowpack.

Sweet, sweet firnspiegel crust at 9,800' on E aspect in the North Fork of the Big Wood River. The shiny surface is a thin, water-ice crust. The dull snow is the drifted remnants of the ~1cm snow "storm" from 12/6.