Avalanche Forecast

Archived

Nov 25th, 2020–Nov 26th, 2020

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

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 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

Glacier.

It dumped last night! 30cm in the alpine will freshen things up, but winds will create reactive soft slabs.

Use caution in the lee of alpine and tree-line features. These surface slabs could provide enough mass to trigger the deeper persistent slab.

Weather Forecast

Unsettled in the wake of yesterday's cold front, expect flurries with gusty winds.

Wed: Isolated flurries with trace amounts, mod W winds, Alp high -9*C

Thurs: Isolated flurries,-9*C, mod SW winds

Fri: Flurries, 5cm, mod/strong SW winds, Alp high -3*C

Snowpack Summary

30cm overnight with SW'ly winds increasing in the last few hours will be forming storm slabs in alpine lee and exposed features. The Nov 5th crust complex (3-10cm thick) is now buried over 1m deep and can be found up to 2500m on all aspects; with facets above and below, this is an active weak layer that will persist for a long time.

Avalanche Summary

With 30cm overnight and increasing SW'ly winds, expect a natural avalanche cycle from steep alpine features (Macdonald, Tupper, N Cheops). Where the new storm slabs dig down to the Nov 5 crust/facet layer, large avalanches to sz 3 can be expected.

If you observe an avalanche or have useful snowpack info, please post to the MIN on the AvCan site.

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.