Avalanche Forecast

Issued: Mar 20th, 2022 4:00PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs.

Avalanche Canada wlewis, Avalanche Canada

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North Rockies.

Wind loaded features remain the primary concern. 

Slab avalanches may propagate wider than you expect where they sit over buried weak layers. 

Summary

Confidence

Moderate - Uncertainty is due to the complexity of the snowpack’s structure.

Weather Forecast

SUNDAY NIGHT: Mostly cloudy with 3-8 cm overnight. Freezing levels between 500-1000 m. Light southwest winds.

MONDAY: Flurries continue with light southwest winds. Freezing levels rise to 1800 m, alpine highs of +2. 

TUESDAY: Freezing levels remain high, reaching toward 2500 m. Up to 10 mm of rain is expected. Strong southwest winds. Alpine high of +6 expected.

WEDNESDAY: 5 cm forecast with freezing levels dropping to 1500 m over the day. Moderate southwest winds. Alpine high of 0. 

Avalanche Summary

Avalanche activity has been tapering off over the week, with a natural cycle observed last on Wednesday. Explosive control also produced size 3 storm snow avalanches. Reactivity now appears limited to slab avalanches in wind loaded features, up to size 2, and some loose dry sluffing out of steep terrain. 

Small loose wet avalanches were seen on all aspects below the freezing line the past 5 days, and on sun affected slopes at all elevations. Even short bursts of spring sunshine can have a significant effect on the snowpack. 

Snowpack Summary

Up to 80 cm over recent storm snow sits over a weak surface hoar layer in sheltered terrain, and on a sun crust on south facing slopes. The surface hoar hasn't shown activity in avalanches observations since Wednesday, however snowpack tests still indicate it is weak and reactive. The most concern is in wind loaded features, of the Pine Pass and the Renshaw area. 

At higher elevations consistent southwest winds are creating deeper deposits on north through east facing features. Below 1500 m, moist snow or a melt-freeze crust likely exists from recent rain and warm temperatures.

The mid and lower snowpack is generally well-settled and strong in most areas, with multiple crusts throughout. 

Terrain and Travel

  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

Problems

Wind Slabs

An icon showing Wind Slabs

Moderate southwest winds have formed wind slabs at higher elevations. 

These slabs may be surprisingly deep and propagate widely where they are sitting on a weak layer of surface hoar in sheltered treeline terrain features, or a sun crust on south facing slopes.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Mar 21st, 2022 4:00PM

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