Pro Field Report
Basic Information
Observation Details
Observation Date:
February 7, 2021Submitted:
February 8, 2021Observer:
SAC - VandenBos (off duty)Zone or Region:
Banner SummitLocation:
Langer Area (6,500-9,400')Signs of Unstable Snow
Recent Avalanches?
YesCracking?
IsolatedCollapsing?
IsolatedSnow Stability
Stability Rating:
FairConfidence in Rating:
ModerateStability Trend:
SteadyAdvanced Information
Weather Summary
Cloud Cover:
OvercastWind:
Moderate , NWNew/Recent Snowfall:
15-20cmWinds blowing MgS, digging well down into terrain that is generally sheltered. Highway was drifted almost to the centerline with 1-2' drifts in places.
Avalanche Observations
Saw evidence of small wind slabs that had failed naturally (thin crowns and small, recent debris piles). No evidence of slides failing on deeper weak layers, but visibility was pretty bad.
Snowpack Observations
Went looking for the behavior of 1/27 interface and the effect of the wind. 1/27 is buried ~75 cm down, but is difficult to differentiate in many places. Too deep and subtle for handpits to be effective. Dug two pits at ~7,000' and two around 8,000' on solar and shaded aspects. Did not find any thick layers of standing surface hoar, but did find some SH xtals at this interface. Did not get propagating results in any of my ECTs, just a mixture of ECTNs with hard force (on solars, where coupled with a crust) and ECTXs (on shaded slopes). In one pit dug at 8,200' the 1/27 interface manifested itself as nothing more than a dusty stripe with some pine needles and produced ECTXs. HS ranged from 160cm on lower elevation pits on solars to over 200cm on higher elevation shaded slopes.
It was about as windy as I've seen the Banner Summit area, with drifts covering almost one lane of the highway on the drive north from Stanley. After I left the highway, the wind was moving snow at all elevations, but only really building slabs in exposed middle and (mostly) upper elevation terrain. Wind slabs that I encountered were stubborn to unreactive, with some producing short cracks and others doing nothing at all when stomped on. Impressive cornice formation at upper elevations provided me with some good slope testers - I was able to safely kick off some multi-hundred pound chunks of snow that produced no results when they impacted the slope below aside from some short cracks.
Avalanche Problems
| Problem | Location | Distribution | Sensitivity | Size | Comments |
|---|---|---|---|---|---|
Wind Slab
|
|
Layer Depth/Date: down 30-60cm Comments: Rose filled out based on where I encountered the problem at its worst. Sensitivity between stubborn and unreactive. |
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Persistent Slab
|
|
Weak Layer(s):
Jan 27, 2021 (FCsf)
Comments: Rose filled out based on where I would suspect problem to be at its worst. |
Terrain Use
Off duty tour, felt comfortable on supported slopes in the low 30s without sensitive wind slabs. Might have convinced myself to push slope angle up a bit in similar terrain, but I don't mind low angle pow. Plenty of wild, steep skiing to be done later.