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Archived

Avalanche Forecast

Mar 12th, 2017–Mar 13th, 2017
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
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: Northwest Coastal.

Avoid avalanche terrain on Monday. A large natural avalanche cycle is expected.

Confidence

High -

Weather Forecast

SUNDAY NIGHT: Intense storm continues with another 20-30 cm of snow, extreme southwest winds, and freezing levels climbing.MONDAY: Another 10-20 cm during the day, extreme southwest winds, freezing levels peak at about 1000 m with alpine temperatures around -2 C .TUESDAY: The next pulse brings 10-30 cm starting late Monday night, strong southwest winds, freezing level dropping with alpine temperatures around -5 C.WENDESDAY: Lingering flurries with 10-20 cm, moderate southwest winds, alpine temperatures around - 7 C.

Avalanche Summary

No new avalanches were reported on Saturday. On Friday, a size 3 persistent slab avalanche was triggered on southwest slope by wind-loading on the February facets. There was also a report of a remotely skier-triggered avalanche on a small convexity, another sign persistent weak layers are primed for triggering.The current storm has all the ingredients for large widespread storm slabs. On top of that, it will also trigger very large persistent slab avalanches on buried weak layers.

Snowpack Summary

By Monday morning storm snow totals may reach 40-80 cm with deeper deposits in lee terrain. Rising temperatures will make the storms slabs very reactive. The new snow will also stress a weak interface from February composed of facets, crust, and surface hoar buried over a metre deep. This layer has produced avalanches and alarming snowpack test results on a regular basis for the past week. The lower snowpack is strong, with the exception of basal facets in shallow snowpack areas around Bear Pass and Ningunsaw.

Avalanche Problems

Storm Slabs

Large natural storm slab avalanches are expected in all avalanche terrain on Sunday.
Travel in avalanche terrain is not recommended with current conditions.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely - Certain

Expected Size: 2 - 3

Persistent Slabs

The new snow will also trigger large avalanches on a reactive weak layer buried over a metre deep.
Be aware of the potential for full depth avalanches due to deeply buried weak layers.Avoid all avalanche terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 2 - 4