Avalanche Forecast

Issued: Nov 28th, 2021 4:00PM

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

Avalanche Canada ahanna, Avalanche Canada

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Sunday's storm produced large natural avalanches. Storm slabs are likely to remain reactive Monday due to sustained warm temperatures. Continue to make conservative terrain choices at this time.

Summary

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

As the snowfall tapers Sunday night, we'll see a brief break Monday before yet another storm arrives Tuesday.

Sunday night: Flurries, 5-10mm tapering by morning. Wind easing to moderate and shifting west. Freezing level 1800 m.

Monday: Scattered flurries bringing a trace then clearing. Light to moderate westerly wind. Alpine temperature around -2 C. Freezing level 1700m.

Tuesday: 10-20 cm new snow. Moderate southwest wind increasing to strong. Freezing level 1600 m. 

Wednesday: 10-20 cm new snow. Strong southwest wind. Freezing level rising to 2300 m.

Avalanche Summary

On Sunday, a widespread natural storm slab avalanche cycle was observed up to size 3 and running to valley bottom along the Highway 1 corridor near Revelstoke. Explosive control work at alpine and treeline elevations produced storm slabs up to size 2.5, some notables entraining loose wet and running full path.

On Friday, a natural storm slab avalanche cycle was observed size 2-3. Multiple size 1 and 1.5 avalanches were triggered by explosives and skiers near Revelstoke. The Mountain Information Network received several reports of reactive storm snow. Whumpfing and cracking within the storm snow was seen on low and steep angle terrain, at treeline and above. By Saturday, avalanche activity had largely subsided, the only reports being a few small skier controlled soft slabs on convex rolls.

Snowpack Summary

Close to a meter of recent snow in the alpine is likely settling quickly in the warm temperatures. At lower elevations where recent precipitation fell as rain, the upper snowpack is wet and dense. This snow has seen redistribution by south to southwest winds at treeline and alpine elevations. In some areas a rain crust may exist at the interface between recent storms.

The mid November crust is up to 5cm thick and found down 60-150cm with faceting below the crust. The lower snowpack contains several early season crusts which appear well bonded.

Snowpack depths exceed 300cm at treeline and alpine elevations, while below 1600m depth decreases rapidly with elevation. 

Terrain and Travel

  • Use conservative route selection and resist venturing out into complex terrain.
  • Stick to simple terrain and be aware of what is above you at all times.
  • Avoid lingering or regrouping in runout zones.

Problems

Storm Slabs

An icon showing Storm Slabs

Large (size 2-3) natural storm slab avalanches were observed Sunday. Storm slabs are likely to remain reactive Monday due to sustained warm temperatures.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Nov 29th, 2021 4:00PM

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