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Avalanche Forecast

Archived

Nov 28th, 2021–Nov 29th, 2021

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

Regions

North Rockies.

Unprecedented early season storms demand an extra conservative approach to mountain travel. This is a time to measure your exposure to avalanche terrain extremely carefully. By Tuesday it will be time to avoid it entirely.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Sunday night: Cloudy with continuing flurries bringing 5-15 cm of new snow. Possibility of localized enhanced accumulations. Moderate to strong west winds.

Monday: Clearing then clouding over in late afternoon. Moderate west winds, increasing overnight. Treeline high temperatures around -3.

Tuesday: Cloudy with increasing flurries bringing 10-20 cm of new snow, increasing overnight. Strong to extreme southwest wind. Treeline high temperatures around 0C with freezing levels rising to 1800 metres.

Wednesday: Cloudy with continuing snowfall bringing 10-20 cm of new snow and storm totals to 40-80 cm. Light to moderate southwest winds. Treeline high temperatures around -3 with freezing levels reaching 1500 metres.

Avalanche Summary

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 was caught in an avalanche and did not survive. This section will be updated as we receive additional information.

A Mountain Information Network incident report was posted on the same day and in the same general area as this fatal incident. It's unknown if the MIN report is describing this fatal incident or not. In either case, the photo and data in the MIN report provides valuable information about conditions in the region.

Saturday, a rider was caught in an avalanche in the Pine Pass area. Search and rescue response is ongoing, but no other details were available at the time of publishing. 

There is evidence that an avalanche cycle occurred in the north of the region on Thursday. Avalanches ranged from size 1 to size 2.5, with the majority starting around treeline. 

A steady storm pattern in the region has given the snowpack little time to stabilize between snowfalls, which means similar conditions will almost certainly prevail on Monday.

Snowpack Summary

Recent winds have scoured exposed ridges, and loaded lee slopes with reactive wind slabs. This trend continued over Sunday night with yet another dose of snow and wind.

In areas sheltered from the wind, new storm slabs have been forming on all aspects.

At elevations below treeline that saw rain earlier in the week, the new storm snow will be covering a crust that formed overnight on Friday. 

Recent observations suggest snow depths below treeline are around 75-100 cm with very little snow below 1400 m. Expect the alpine snowpack to be 150 cm or more.

 

In the Pine Pass area, expect to find a deeper snowpack than the rest of the region. The last storm dropped up to 80 cm of snow there over 2 days. 

The lower snowpack mostly 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.

Terrain and Travel

  • Use careful route-finding and stick to moderate slope angles with low consequences.
  • Avoid freshly wind loaded terrain features.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.

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.