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Archived

Avalanche Forecast

Feb 23rd, 2020–Feb 24th, 2020
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: South Coast.

Recent snow rests on a weak layer so it may take longer than usual to bond to old surfaces and will likely remain reactive to human traffic. Continue to make conservative terrain choices while storm snow settles and stabilizes.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

Sunday night: Up to 5 cm new snow. Strong northwest wind. Freezing level 500 m.

Monday: Mix of sun and cloud. Moderate northwest wind.Freezing level 700 m.

Tuesday: 5-10 cm new snow. Moderate southwest wind. Freezing level 700 m.

Wednesday: Cloudy. Light to moderate northwest wind. Freezing level 1000 m.

Avalanche Summary

Although we have not received reports yet, a natural storm slab avalanche cycle is anticipated to have occurred Sunday during the storm with storm slabs sliding on the surface hoar/crust bed surface.

Snowpack Summary

30-60 cm of recent snow has been redistributed by strong southwest to northwest winds at upper elevations, and sits over a layer of surface hoar on a breakable crust. The surface hoar/crust combo makes an excellent bed surface for avalanches. The remainder of the snowpack is well-settled.

The snowpack depth varies from around 200 to 250 cm at the peaks of the North Shore mountains (1400 m) and rapidly decreases with elevation to no snow below 1000 m.

Terrain and Travel

  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.

Avalanche Problems

Storm Slabs

Storm slabs could reach 30 to 40 cm in thickness by midday Sunday, which overlies a weak layer of surface hoar crystals. Weather models are showing snowfall rates of up to 5 cm an hour Sunday morning. The snow will also fall with strong to extreme southwest wind, which will form slab properties within the snow quickly, particularly at treeline and alpine elevations. This is all a recipe for a natural avalanche cycle to occur on Sunday.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 2.5