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Avalanche Forecast

Archived

Dec 30th, 2020–Dec 31st, 2020

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

Regions

Glacier.

If we get the 10cm of new snow, and moderate wind; the hazard in the Alpine may rise to considerable.

Weather Forecast

A weak warm front draped over Rogers Pass bringing light precipitation (5-10cm) today and tonight. Freezing levels will remain near valley bottoms. Mountain top winds could reach moderate. The front will also slowly fizzle out tonight. Flurries tomorrow with the FL rising to 1100m, and light SW winds. Friday through the weekend is looking STORMY!

Snowpack Summary

Approximately 25cm of new snow has fallen over the last few days, burying another surface hoar layer. Reports that the new snow is relatively right side up, with isolated storm slabs that are stubborn to trigger. This interface will become touchy in the coming days as it gets overloaded with storm snow and warm temperatures.

Avalanche Summary

There were MIN reports of skiers triggering loose dry avalanches up to size 2 in steep terrain, and one small storm slab in an immediate lee at treeline.

There was a natural size 2.5 storm slab from steep North facing terrain on Mt Macdonald.

Several very large avalanches last week failed on the early December crust, facet/surface hoar combo.

Confidence

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.