Avalanche Forecast
Issued: Dec 13th, 2021 1:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
JSmith,
VIAC
Shifting winds continue to form fresh wind slabs that are possible to human trigger. Pay attention to changing conditions with elevation/aspect and avoid slopes that have been freshly wind-loaded.
Summary
Confidence
Moderate - Uncertainty is due to the limited number of field observations.
Weather Forecast
MONDAY NIGHT: Clearing skies / Light, northerly winds / Low of -7 C / Freezing level 500 m.
TUESDAY: Mostly sunny / Light, northwesterly winds / High of -1 C / Freezing level 600 m.
WEDNESDAY: Cloudy with flurries; 5-10 cm. / Strong, southerly winds / High of -1 C / Freezing level 600 m.
THURSDAY: Mix of sun and cloud / Moderate, northwesterly winds / High of 0 C / Freezing level 700 m.
Avalanche Summary
On Saturday, there were reports of numerous small (size 1-1.5) avalanches releasing 30-70 cm deep in the storm snow across a variety of aspects. See this MIN report from the Mt. Washington area for a helpful visual.
Snowpack Summary
An impressive storm over the weekend brought 50-90 cm of snow to the mountains. A gradual rise in temperature during the storm formed a crust layer that can be found in areas up to 1400 m. An additional 20-50 cm of snow has accumulated since temperatures cooled.Â
Strong southerly winds have had an ample supply of snow to drift into wind slabs at upper elevations. It remains possible to trigger these wind slabs in lee terrain features, such as down-wind of ridges and roll-overs.
Monitor for changing conditions as you move into wind-exposed terrain and pay attention to cracking or hollow sounds.
Below the early December crust layers, the snowpack is generally well-settled. With this storm event, a greater number of areas below treeline are exceeding threshold snow depths for avalanches.Â
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Be aware of highly variable recent wind loading patterns.
- Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
Problems
Wind Slabs
Strong southerly winds and recent snow have formed wind slabs in lee terrain features at upper elevations that may remain possible to human trigger. Shifting winds overnight on Monday may form fresh wind slabs that are more sensitive to triggering.
Aspects: North, North East, East, South West, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 14th, 2021 1:00PM
