Pro Field Report

Basic Information

Observation Details

Observation Date:
December 5, 2020
Submitted:
December 5, 2020
Observer:
SAC - Vandenbos (off duty), Linnet
Zone or Region:
Sawtooth and Western Smoky Mtns
Location:
Fishhook (Mostly northern portion of the compass, 6,500' to 9,800' and low elevation solars)

Signs of Unstable Snow

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

Snow Stability

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

Bottom Line

Found weak snow near the ground on upper elevation slopes on the northern portion of compass. This snow returned unstable snowpack test results.

Advanced Information

Weather Summary

Cloud Cover:
Clear
Wind:
Light , SW

Light S-SW winds on upper elvation ridgelines, calm otherwise. Strong temperature inversion continues to make for relatively mild temperatures up high and very cold air down in the valleys.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Comments Photo
1
N
This thin wind slab failed in the Sawtooths during the wind event at the beginning of January.

Observed a very small wind slab in the alpine that had likely failed during the wind event last week. No other avalanche activity observed. N facing slope at 9,300'

Snowpack Observations

Found some fairly ugly, dry DH near base of snowpack on N facing slope at 8,900'. Cups averaged 2-3mm with some grains up to 4mm. DH was sitting on 1F+ to P- crust, which was somewhat irregular thanks to slope roughness. Produced ECTP30 down 80-90cm. Did a single CPST which produced a CPST 70/100 END. I'd flag this result as unrepresentative as the weak layer was interrupted by talus in places and it was tough to get the saw to track well. Was pressed for time and did not perform repeat tests. Based on the appearance of DH, the fact that we've already seen some activity on this interface in the Sawtooths I don't think we are out of the woods yet with this snow.

11/17 interface is dusty and obvious in pit wall but is not producing signs of instability at this point. There is a crust at this interface where I dug.

Low elevation snowpack is also particularly concerning in the Sawtooths. The combination of a stout rain crust down 20-30cm under an impressively weak facet stack capped with well developed 2-8cm SH seems likely to produce some avalanche activity in areas that don't often generate avalanches. This style of snowpack exists anywhere the inversion is overlapping the rain crusts. Of course, we need a load to get this going, but there is starting to be some light at the end of the tunnel on that front.

Terrain Use

Navigation choices based both on presence of weak snow near the ground and thin, stiff wind slabs from last week. With thin snow cover and lots of boulders sticking out of the snow still the consequences of even small slides could be high.