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Avalanche Forecast

Archived

Nov 28th, 2019–Nov 29th, 2019

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

Glacier.

The Winter Permit System is now in place, keep this in mind in your trip planning.  Cold temperatures and short days , plan accordingly.

Weather Forecast

A cold clear day is forecast with continued North through East winds bringing arctic air into the forecast area.  No precipitation is forecasted and freezing levels will stay well below valley bottom. It will be cold and clear tonight and right through to the weekend.

Snowpack Summary

Strong Northerly winds have redistribute last weekend's storm snow on alpine and treeline lee features, caution, reverse loading. Cold temperatures should soften former surface slabs in protected areas. The 2 main layers to watch for are the Nov 23rd Surface Hoar, buried 30-50-cm, and the Nov 17th interface.

Avalanche Summary

Limited natural avalanche activity observed yesterday, one size 1.5 slab release in Lone Pine in the highway corridor. Sunday's storm produced a decent natural avalanche cycle to size 3 in Rogers Pass. Avalanche activity has tapered off since the end storm.

Confidence

Due to the number of field observations

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.