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Avalanche Forecast

Archived

Nov 30th, 2020–Dec 1st, 2020

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.

Wind spikes today mean windslabs will remain an active avalanche problem for the next couple of days.

Weather Forecast

A weak frontal system gives flurries and a spike in winds today. Then a ridge of high pressure gives clear skies and warm temps for the rest of the week.

Today: Flurries (5cm), Alpine High -7 C. Ridge wind (RW) mod SW (gusting strong), Freezing level (FzL) 900m

Tonight: Cloudy. Low -11 C. RW moderate NW

Tuesday: Sunny. High -1 C. FzL 2500m

Snowpack Summary

Surface hoar up to 8mm has grown on the surface at and below treeline. Variable wind effect at ridgetops from SW winds. A layer of small rounding surface hoar has been found down 40-60cm in isolated areas at treeline. The Nov 5 crust is now between 90 and 140cm down which remains within the triggerable range for skiers and riders in some areas.

Avalanche Summary

An avalanche reported on Mt Swanzy appears to have stepped down to the Nov. 5th weak layer. Numerous large natural avalanches occurred Friday night on all aspects in the hwy corridor, as well as in the backcountry. A skier triggered sz 1.5 in Avalanche Crest and a 2.5 in Quartz last week failed on surface hoar with wide propagation.

Confidence

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.