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Avalanche Forecast

Archived

Nov 30th, 2021–Dec 1st, 2021

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Northwest Coastal.

Reactive storm slabs are likely. 

Continued snowfall and cranking wind is keeping the avalanche danger HIGH. Be patient as the recent storm snow needs time to settle and stabilize. 

Confidence

Moderate - Uncertainty is due to difficult to forecast freezing levels.

Weather Forecast

Freezing levels will drop faster and cooler in the Northern half of the region. 

Tuesday Night: 10 – 15 mm of precipitation falling as snow in the alpine and rain at lower elevations. Freezing levels dropping to 900 m with alpine temperatures near -3. Ridgetop wind remains strong from the southwest.

Wednesday: 10-15 mm of precipitation and freezing levels dropping to 800 m. Alpine temperatures near -2. Ridgetop wind strong from the southwest.

Thursday: Snow 10-20 cm. freezing levels 300 m and alpine temperatures near -7. Ridgetop wind strong from the southwest. 

Avalanche Summary

Natural avalanche activity will likely continue with more snow and strong southwest wind on Wednesday. 

On Tuesday morning several size 2 storm slabs were reported. They ran naturally during the storm.

Over the weekend, several large natural storm slabs (size 2-3) were reported in the last 24 hours in the alpine as well as some small wet snow avalanches near the rain line.

Snowpack Summary

Strong southwest wind and 30-60 cm of recent storm snow fell at upper elevations building new and reactive storm slabs. This new snow sits on buried wind slabs in the alpine. Lower elevation snow became moist with the rain, however; with freezing levels falling by Tuesday night (400 m- 700 m) a crust will likely form. 

Treeline snowpack depths are estimated to be around 200-300 cm and a prominent crust can be found near the base of the snowpack. 

In the Northern part of the region (Bear Pass) two weak layers of surface hoar have been reported in sheltered areas at treeline.  

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • Avoid the runout zones of avalanche paths. Avalanches could run full path.
  • The new snow may require another day to settle and stabilize.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.