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Avalanche Forecast

Dec 21st, 2019–Dec 22nd, 2019
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
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
3: Considerable
The avalanche danger rating in the alpine will be considerable
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: Lizard-Flathead.

Precipitation is forecast to continue into Sunday. As a result avalanche danger will remain at HIGH.

Confidence

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

Saturday: Snow, accumulation 15-30 cm. Alpine temperature -2 C. Moderate to strong southwest wind. Freezing level 1600 m.

Sunday: Flurries, accumulation 10-15 cm. Alpine temperature -4 C. Moderate southwest wind. Freezing level 1500m.

Monday: Scattered flurries. Alpine temperature -4 C. Moderate west wind. Freezing level 500 m.

Tuesday: Mainly cloudy. Alpine temperature -4 C. Moderate west wind. Freezing level 500 m.

Avalanche Summary

Snow accumulation over the past 3 days has overloaded deeply buried weak layers. As a result avalanches have the potential to reach the end of their runouts. Expect storm slabs to remain touchy on Sunday as the new snow continues to accumulate at upper elevations. On Friday and Saturday there were reports of widespread avalanche activity in the recent storm snow. Explosives controlled avalanches size 3 persistent slab avalanches were running on weak layers 150 cm deep at treeline on Saturday.

Snowpack Summary

Snowfall at upper elevations has covered a previously variable and wind-affected surface and is expected to continue to develop touchy storm slabs. Expect the surface snow at lower elevations to be moist or wet due to rain.

Crust layers from November and October can be found 40-100 cm below the surface. These layers produced large avalanches with explosive triggers around Dec 13-14, but since then have appeared to gain strength, but may become overloaded with all the recent snow.

Snowpack depths range between 60-130 cm at higher elevations and taper rapidly below treeline.

Terrain and Travel

  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.

Avalanche Problems

Storm Slabs

Snow at upper elevations keeps coming. Storm slabs continue to build through Saturday night. Expect to see wet snow avalanches at lower elevations due to rain below 1500m.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1.5 - 3

Storm Slabs

Snow and/or rain has continued accumulate over the past 3 days and is likely overloading deeply buried weak layers.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 2 - 3.5