Avalanche Forecast

Issued: Nov 30th, 2021 4:00PM

The alpine rating is high, the treeline rating is high, and the below treeline rating is high. Known problems include Storm Slabs.

Avalanche Canada ahanna, Avalanche Canada

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Storm slabs will remain reactive Wednesday. Avoid avalanche terrain while the snowpack adjusts to the new snow load.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Highest snowfall amounts are concentrated around the Alberta elbow.

Tuesday night: 10-20 cm new snow. Strong to extreme southwest wind. Freezing level dropping 2000 to 1200 m.

Wednesday: 5-10 cm in the morning, clearing in the afternoon. Moderate to strong westerly wind. Freezing level 1000 m. 

Thursday: A mix of sun and cloud with isolated flurries. Moderate westerly winds. Freezing level valley bottom.

Friday: A mix of sun and cloud. Moderate southwest winds. Freezing level valley bottom.

Avalanche Summary

We suspect a widespread natural avalanche cycle to have occurred Tuesday night during the peak of the storm.

A fatal avalanche involvement occurred in the Hasler riding area on Saturday. We have preliminary information that indicates a party of four snowmobilers were in the area when one person triggered and was caught in an avalanche and did not survive. This section will be updated as we receive additional information.

Also on Saturday, a very large natural avalanche was reported to the Mountain Information Network from the Core Lodge riding area.

A Mountain Information Network report from Sunday provides valuable information about conditions in the region ahead of this week's storm.

Snowpack Summary

Storm totals are expected to be in the range of 20-50 cm. A spike in temperature Tuesday evening may have resulted in crust formation within the storm snow as high as 1800 m. Strong winds have likely resulted in deeply loaded pockets in lee terrain features at alpine and treeline elevations.

A steady storm pattern has given the snowpack little time to stabilize between snowfalls. Underneath around 1 m of all this recent storm snow lies a rain crust.

The lower snowpack consists of a series of early season crusts. These appear to be strong, but shallow alpine slopes along the eastern side of the Rockies towards Jasper may have weaker, faceted snow near the ground. Anywhere this type of basal snowpack condition exists is a serious concern with recent loading. There is potential for storm slab releases to trigger deeper snowpack layers and produce very large avalanches in these areas. 

Snowpack depths are anticipated to be approaching 3 m in the alpine and around 1 m at treeline. Pine Pass area is currently the leader for snowpack depths so far this season and is expected to be a focal point for the current storm as well.

Terrain and Travel

  • The new snow may require another day to settle and stabilize.
  • Only the most simple non-avalanche terrain free of overhead hazard is appropriate at this time.
  • Avoid areas with overhead hazard.

Problems

Storm Slabs

An icon showing Storm Slabs

Fresh storm slabs will be reactive on Wednesday.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely - Almost Certain

Expected Size

2 - 3.5

Valid until: Dec 1st, 2021 4:00PM