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Archived

Avalanche Forecast

Mar 6th, 2017–Mar 7th, 2017
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
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
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
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Lizard-Flathead.

A week of heavy snowfall and strong winds has left large storm slabs and cornices primed for human triggering. Avoid overhead hazards and stick to mellow terrain.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

We're looking at occasional flurries and cool temperatures throughout the forecast period. TUESDAY: Flurries with up to 5 cm of new snow, 20-40 km/h southeast winds, alpine temperatures around -9 C. WEDNESDAY: Flurries with 5-10 cm of new snow, 20-30 km/h east winds, alpine temperatures around -8 C. THURSDAY: Cloudy with scattered flurries and up to 3-5 cm of new snow, 30-50 km/h east winds, alpine temperatures around -12 C.

Avalanche Summary

Cornices are large and remain easy to trigger. See here for a great MIN post from Sunday illustrating just how surprising the results can be.Several size 1.5 to 3 natural and explosives triggered avalanches were reported on Saturday. Aspects were east through northwest, from 1500m to ridgetop.A widespread natural avalanche cycle occurred on Friday night, with many size 2-3 cornice triggered avalanches on north and east aspects. Natural activity is expected to taper off, but storm slabs will remain possible for human triggering.

Snowpack Summary

Another 10-20 cm of snow fell on Sunday into Monday, bringing the weekly total to over 115 cm. Strong southwest winds have extensively redistributed the snow and formed large brittle cornices.The new snow came in "upside down" (heavier, denser snow over lighter snow) and is rapidly settling into a slab which sits over a variety of old surfaces including surface hoar, facets, stiff wind slabs, sun crusts, and a rain crust below 1900 m.Isolated basal weaknesses may still exist in shallow snowpack areas and appear to isolated to north-northeast aspects in the alpine.

Avalanche Problems

Storm Slabs

Storm slabs remain likely for rider triggering, especially on leeward slopes and behind terrain features that are wind loaded.
Avoid leeward slopes as a thicker, reactive slabs will likely exist.The new snow will require several days to settle and stabilize.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 3

Cornices

Always look up and avoid exposure to overhead cornices.
Do not travel on slopes that are exposed to cornices overhead.Stay well back from cornices.

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

Elevations: Alpine.

Likelihood: Likely

Expected Size: 1 - 3