Professional Observation
Basic Information
Observation Details
Observation Date:
March 1, 2021 - March 4, 2021Submitted:
March 5, 2021Observer:
WAC - Caleb MerrillZone or Region:
Northern WallowasLocation:
Big Sheep DrainageSigns of Unstable Snow
Recent Avalanches?
None ObservedCracking?
IsolatedCollapsing?
None ExperiencedSnow Stability
Stability Rating:
GoodConfidence in Rating:
ModerateStability Trend:
ImprovingBottom Line
During 4 days in the Big Sheep drainage, we encountered just about every type of snow surface conditions. Above treeline on North through East aspects, one could find windslab, "windboard", and cross loaded surfaces. Lower elevation protected north facing terrain held soft turnable snow. Solar aspects offered a melt freeze surface with a high level of variability in its supportiveness. Cornices were large and drooping over leeward start zones. In protected shady areas (N-E aspects) near treeline, pockets of Surface Hoar was forming (2-5mm).
The upper snowpack seems to be consolidating well around the 2/22 rain crust, however my uncertainty lies within a layer that is 10 cm (4") below the rain crust (approximately 50 cm (20") from the surface. No propagation was experienced in Extended Column Tests, however planar results were observed on this layer in compression tests once the 2/22 crust was impacted with moderate force.
Manageable Wet Loose Avalanches and lingering stubborn windslabs were our main concern through our backcountry travel. Avoidance of these predictable avalanche problems was our strategy.
Media
Advanced Information
Weather Summary
Cloud Cover:
Mostly SunnyWind:
Light , SWMost of the snow available for transport was moved around on 3/1 and 3/2, loading mostly North through East aspects. Temperatures rose throughout the week, topping out in the upper 30's on Thursday.
Avalanche Observations
A D2.5 avalanche was observed near Pete's Point that looked to be a large windslab. Timing unknown.
Snowpack Observations
North and East aspect pits near 8k':
ECTN (no propagation) failing on density changes above 2/22 Rain Crust.
Moderate Resistant Planar Compression test results in layers above 2/22 Rain Crust.
Moderate BREAK result through 2/22 Rain Crust
Hard Resistant Planar result on layer 10 cm below 2/22 Rain Crust
Avalanche Problems
| Problem | Location | Distribution | Sensitivity | Size | Comments |
|---|---|---|---|---|---|
Wet Loose
|
|
Layer Depth/Date: up to 40 cm Solar Aspects, more active in the afternoon |
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Wind Slab
|
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Layer Depth/Date: up to 50 cm North through East Aspects Near and Above Treeline |
Terrain Use
We used a "cautiously stepping out" mindset for the week.
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