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Avalanche Forecast

Archived

Feb 13th, 2020–Feb 14th, 2020

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Lizard-Flathead.

New snow and continuing southwest wind should resupply our wind slab problem for Friday. Monitor the depth and reactivity of new snow as you travel and increase caution around areas that are being actively wind loaded.

Confidence

High -

Weather Forecast

Thursday night: Cloudy with flurries bringing 5-10 cm of new snow. Moderate to strong southwest winds.

Friday: Mainly cloudy with continuing light flurries and about 5 cm of new snow. Moderate west winds. Alpine high temperatures around -8.

Saturday: Cloudy with scattered flurries bringing a trace to 5 cm of new snow, increasing a bit overnight. Moderate southwest winds, becoming strong at ridgetop. Alpine high temperatures around -7.

Sunday: Cloudy Cloudy with easing flurries bringing up to 5 cm of new snow. Light west winds. Alpine high temperatures around -7.

Avalanche Summary

New avalanche observations from Tuesday were limited to a few small (size 1) wind slabs able to be skier triggered in crossloaded gully features. Observations into the alpine were limited by poor visibility. Wednesday's reports showed a transition to small dry loose releases.

On Monday control work produced a cornice failure from a northeast facing ridge, a couple of size 2 wind slabs on a northwest facing feature at 2000 m and small stubborn wind slabs to size 1.  

Last Saturday storm slab avalanches to size 2 were widespread as a result of more active weather. They ran naturally and were intentionally triggered by avalanche control work on all aspects.

Snowpack Summary

15 to 25 cm of storm snow from last weekend is on a positive stabilizing trend, with mainly small wind slabs resulting from a mix of northeast and more recent southwest winds remaining as surface instabilities. This recent snow rests on previously wind affected snow and a thick rain crust that exists up to roughly 2100 m. In many areas this capping crust extends to mountaintops. 

Sheltered areas now have 15-30 cm of snow above the crust. The bottom 20 cm of the snowpack consists of basal facets and decomposing crusts that have not been an active avalanche problem since December, but could reemerge as a problem after sustained warming.

Terrain and Travel

  • Caution around slopes that are exposed to cornices overhead.
  • Small avalanches can have serious consequences in extreme terrain. Carefully evaluate your line for wind slab hazard before you commit to it.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.