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Avalanche Forecast

Archived

Dec 23rd, 2021–Dec 26th, 2021

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Waterton Lakes.

The storm has arrived bringing 20 cm snow high winds and warm temps. Over the next few days expect to see storm slabs become more reactive as more snow continues to load weak layers.

Weather Forecast

Friday: Overcast and snowing up to 20 cm. Light NE winds. Alpine temps high -12. Freezing levels valley bottom

Saturday: Overcast and snowing 15 - 20 cm.  Light NE winds. Alpine temps high -16. FL valley bottom.

Sunday: Overcast with flurries, amounting to 5 cm. Light NE winds. Alpine temps high -30. FL valley bottom.

Snowpack Summary

20 cm new snow and variable winds are creating storm slabs and crossloading features.  Warm temps are promoting cohesion of storm slabs. New snow overlies a series of previous windslabs 20-60 cm thick in AL/TL. This sits atop facets above Dec 4 crust. A 20-60 cm thick Nov MFcr complex completes the snowpack to ground. HS at TL is 110 - 170.

Avalanche Summary

No new avalanches reported in park with very limited visibility in the last few days. Operation north and west of the park are reporting several wind slabs up to size 2. If you go out into the mountains please share your observations on the Mountain Information Network.

Confidence

Intensity 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.

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.