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Avalanche Forecast

Feb 20th, 2012–Feb 21st, 2012
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
4: High
The avalanche danger rating below treeline will be high
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
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
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: South Coast.

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

The arrival of the next frontal system should come Monday night into Tuesday bringing light-moderate snowfall amounts which will intensify later Tuesday into Tuesday night.Tuesday: New snow up to 15cm. Ridgetop winds 40-50km/hr from the West. Treeline temperatures near -3, with freezing levels up to 1500m. Wedneday: Snow amounts 5-10cms. Ridgetop winds from the West reaching 70-90km/hr, slowly dying to 40-60km/hr in the afternoon. Freezing levels falling to 1000m. Thursday: Trace amounts. Ridgetop winds from the NW 50-70km/hr.

Avalanche Summary

Coquilhalla Area: Skier triggered size 1 was reported. This occurred on an East aspect, @ 1845m. The crown was 20cm deep, and 10m wide. Another skier triggered avalanche size 1.5 occurred on a North aspect @ 1460m. This was below treeline in a gully feature. Both avalanches failed on the buried weak layer that exists below the new storm snow. No injuries reported.Duffy Lake area: On Saturday a size 2 rider triggered avalanche was reported, to see more details visit our incident report database: https://avalanche.ca/cac/library/incident-report-database/view/ffa0801e-2d0e-48e8-b480-5b6068d5a8bb

Snowpack Summary

Over the weekend up to 20cm of new snow fell over the Duffy Lake area. The Coquihalla has seen up to 40cm. This new snow has buried a variety of old snow surfaces that formed during a sunny dry spell over the past 2 weeks. These surfaces include: melt-freeze crusts on all aspects below 1700m and on steep solar aspects higher up, surface hoar (feather like crystals), old wind slabs, and facets (sugary crystals), which exist on north aspects as well as around crusts. The surface hoar seems to be most prominent in sheltered treeline locations and below, and most likely found in the north and central parts of the region. We may see these buried weak layers become naturally reactive with forecast snow and wind, and likely susceptible to rider triggers. Generally below this sits a well settled snowpack, with treeline snowpack depths near 250cm. For insight on incremental loading, and the "Tipping Point" check out our latest Forecaster's Blog.

Avalanche Problems

Wind Slabs

Moderate-Strong winds will blow around the new snow creating wind slabs on lee slopes. As these slabs build, they will increase the load on buried weak layers. These weak layers are likely to reach threshold, and the avalanche danger will rise.

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

Elevations: Alpine.

Likelihood: Likely - Very Likely

Expected Size: 1 - 5

Persistent Slabs

New snow up to 15cm expected on Tuesday, with an additional 10cm overnight. Amounts look to be higher in the Coquihalla area. This new snow may create touchy storm slabs that sit on a variety of buried weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 5