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Avalanche Forecast

Dec 6th, 2019–Dec 7th, 2019
Alpine
4: High
The avalanche danger rating in the alpine will be high
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
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
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

Regions: North Columbia.

Storm snow will continue to accumulate Friday night and through Saturday as a frontal system stalls over the region. This will raise the avalanche danger to HIGH.

Confidence

No Rating - Uncertainty is due to the timing, track, & intensity of the incoming weather system.

Weather Forecast

Friday Night: Snow, 10-20 cm, alpine temperature -3 C, moderate southwest wind.

Saturday: Snow, 10-15 cm, alpine temperature -4, moderate southwest wind.

Sunday: Sunny with cloudy periods, alpine temperature -10, moderate north wind.

Monday: Sunny with cloudy periods, alpine temperature -8, moderate northwest wind.

Avalanche Summary

Recent reports indicate skier triggered and natural storm slab avalanches to size 2, and cracking on small, supported slopes. There were also a few reports persistent slab avalanches failing on a layer of surface hoar (down 60-80 cm) at treeline elevations. Expect to see an increase in storm and persistent slab avalanches as the new snow continues to accumulate through Friday night and Saturday.

Snowpack Summary

25-45 cm of new snow falling over the past 36 hours has added to the 30-50 cm of storm snow from early in the week. All this new snow has covered a thick layer of faceted crystals, previously wind-affected surfaces, and/or surface hoar in sheltered areas around treeline and below.

A layer of surface hoar (feathery crystals) may be found in sheltered areas around treeline down 50-80 cm. In some areas this may be sitting on a crust.

A variety of crusts from late October are buried deeper in the snowpack. Total snow depths range from 120-150 cm around tree line.

Avalanche Problems

Storm Slabs

Storm slabs will develop through Friday as snowfall accumulates around the region, adding to snow from early this week. Expect new storm slabs to develop, and be wary of recently developed slabs hiding under fresh snow.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 2.5

Persistent Slabs

A buried weak layer of surface hoar and possibly a crust can be found in the middle of the snowpack. While difficult to trigger, avalanches failing on this layer would be large.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood: Possible

Expected Size: 1 - 2