Professional Observation
Basic Information
Observation Details
Observation Date:
December 29, 2019Submitted:
December 29, 2019Observer:
SAC - Martin StefanZone or Region:
Galena Summit and Eastern MtnsLocation:
Prairie PeakSigns of Unstable Snow
Recent Avalanches?
None ObservedCracking?
IsolatedCollapsing?
IsolatedSnow Stability
Stability Rating:
FairConfidence in Rating:
ModerateStability Trend:
SteadyBottom Line
The wind has done work on the snow at higher elevations, and our weak snowpack structure needs time to adjust to the new load.
Advanced Information
Weather Summary
Cloud Cover:
OvercastTemperature:
mid 20s estWind:
Moderate , NWModerate wind at ridgelines, but snow transport confined to exposed areas close to ridgetop where I was. Looking over the valley, the Boulders looked worse off. Big areas completely scoured, and probably considerable loading in other spots. Looked like drafts through the valleys too, so loading not just confined to ridges.
Snowpack Observations
Ongoing intermittent wind transport in exposed areas at mid to high elevations, but no large reactive wind slabs where I was. Mostly I found thin (5-15cm) finger to pencil hard slabs that were reactive, the thicker drifts did not respond to stomping or cutting.
My guess is that the shifting wind direction has partially negated the worst of it by first moving snow first in one direction and then in the other.
Where the wind had deposited significant amounts of snow at higher elevation 12/7 and 11/26 were clearly strained. In a sheltered spot at 9100ft NE with HS 85cm I had 12/7 as still well preserved SH at 50cm down giving ECTP24, PST30/100 (end), CPST 25/100 (end). I also had 11/26 65cm down as the nasty DH/MFcr/FC combination we have been seeing, giving CPST30/100(end). The slab on top of 12/7 was 4f-1f hard and definitely has some heft to it, and the pit mirrors very much what Ethan and Chris have seen elsewhere.
Avalanche Problems
| Problem | Location | Distribution | Sensitivity | Size | Comments |
|---|---|---|---|---|---|
Persistent Slab
|
|
Layer Depth/Date: 12/7 SH and 11/26 DH/MFcr/FC At higher elevation the thicker, stiffer wind drifted slab can potentially create large avalanches. |
Terrain Use
I avoided avalanche terrain where the wind had created fresh slabs and steep meadows at lower elevations.
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