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Avalanche Forecast

Dec 19th, 2020–Dec 20th, 2020
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
3: Considerable
The avalanche danger rating below treeline will be considerable
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

Regions: Lizard-Flathead.

New snow, strong wind and rising freezing levels will combine to make dangerous avalanche conditions. Staying out of avalanche terrain and away from overhead hazards is recommended.

Confidence

Moderate - Uncertainties in both the snowpack structure and the weather forecast limit our confidence.

Weather Forecast

SATURDAY NIGHT - Snow, heavy at times 12-25 cm / southwest wind moderate, gusting to strong / alpine low temperature near -2 / freezing level 1200-1500 m

SUNDAY - Chance of flurries with sunny breaks / gusty southwest winds / alpine high temperature near 0 / freezing level 2000 m

MONDAY - Snow/Rain 10-20 cm / southwest wind, 30-40 km/h gusting to 85 km/h / alpine high temperature near 0 / freezing level up to 1700 m 

TUESDAY - Periods of of snow, possibly heavy at times / moderate east winds / freezing levels initially high, but dropping at tail end of storm

Avalanche Summary

On Saturday explosives produced results up to size 2 on the early December crust. On Friday there were a few natural size 2 wind slab avalanches reported in the alpine.

Please consider sharing your observations on the Mountain Information Network. Thank you to those that have already submitted this winter!

Snowpack Summary

Strong wind from the southwest and fresh snow has likely formed new reactive storm slabs. Depending on aspect and elevation 60-100 cm now sits on the early December crust. This crust may have persistent weak, and facetted crystals above and below it. 

Deeper in the snowpack are two hard melt-freeze crusts that formed in November that may have some weak crystals around them. There is uncertainty if and where in the region this may be a problem. Without any recent avalanche activity, it appears that this layer is dormant for the time being.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
  • Don't let the desire for deep powder pull you into high consequence terrain.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

Avalanche Problems

Storm Slabs

New storm snow has likely formed reactive slabs. Strong southwest wind will create deeper slabs on leeward slopes that could produce larger avalanches. Avalanches may entrain moist snow if the runouts extend into below treeline elevations.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 2.5

Persistent Slabs

Depending on elevation and aspect, 50-100 cm of snow currently sits above a buried crust from early December. Sugary, facets above and/or below the crust may weaken the bond and the persistent slab may become reactive, especially to human triggers. 

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1.5 - 3