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Avalanche Forecast

Archived

Jan 17th, 2022–Jan 18th, 2022

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

Regions

Glacier.

Storm slabs on surface hoar turned things "electric" Monday afternoon, especially below treeline. Be wary of steep, gladed lines that did not avalanche during the storm.

Tuesday's sun may naturally trigger S'ly-facing slopes...heads up!

Weather Forecast

A brief ridge will build over the Interior, bringing sunshine, colder temps, and light mtn-top winds.

Tonight: Clearing with flurries, trace ppt, Alp low -11*C, light/gusting strong SW winds

Tues: Sunny periods, Alp high -10*C, light winds

Wed: Cloud with sun/flurries, Alp high -8*C, light SW winds

Thurs: Snow, 20cm, Alp high -5*C, mod/strong SW winds

Snowpack Summary

25-40cm of new snow, coupled with warm temps and mod/strong SW winds, has built storm slabs. The Jan11 surface hoar layer, down 40-60cm, has been extremely touchy with this new load, with numerous natural avalanches starting on this layer. The Dec 1 crust is buried up to 2m deep with weak, faceted snow above and below it.

Avalanche Summary

A natural avalanche cycle involving low elevation (below treeline) storm slabs occurred around noon Monday, with several sz 3's coming close or hitting the highway. Suspect Jan 11 surface hoar layer was sliding layer.

Treeline and above is currently in a natural cycle, with numerous sz 2.5-3's failing on all aspects in the highway corridor.

Confidence

Track of incoming weather systems is uncertain

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.

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.