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Avalanche Forecast

Mar 11th, 2017–Mar 12th, 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
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
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

Regions: Northwest Coastal.

Large avalanches will be widespread for the next few days as the coast gets slammed by a hefty storm.

Confidence

High -

Weather Forecast

SATURDAY NIGHT: Storm intensifying with 10-15 cm of snow and 30-50 km/h south winds.SUNDAY: Stormy with about 20 cm of new snow, 60-80 km/h south winds, alpine temperatures climbing to -5 C.MONDAY: Another 20-30 cm of snow, 70-90 km/h southwest winds, alpine temperatures around 0 C and freezing levels climb to 1000 m.TUESDAY: More snow (15-25 cm), 60-80 km/h south winds, alpine temperatures around -2 C and freezing levels drop to 700 m.

Avalanche Summary

On Friday, wind-loading triggered a size 3 persistent slab avalanche on the February facets on southwest slope. Several cornice and ice falls were reported to entrain loose snow, but did not trigger any slabs. One remotely skier triggered avalanche was reported on a small convexity from 50 m away.The incoming storm has all the ingredients for widespread storm slabs. On top of that, it will also trigger large persistent slab avalanches on buried weak layers.

Snowpack Summary

Expect 20-30 cm of fresh snow on Sunday and thicker, stiffer, and more reactive deposits in lee terrain. The new snow will bury older lingering wind slabs formed by recent outflow winds. The load of the new snow will stress a weak interface buried about 50-80 cm deep composed of facets, crust, and surface hoar. This layer has produced avalanches and alarming snowpack test results on a daily 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 storms slabs will develop rapidly in the upcoming days.
Avoid avalanche terrain during periods of heavy loading from new snow and wind.Travel in avalanche terrain is not recommended with current conditions.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 2

Persistent Slabs

The new snow will likely trigger large avalanches on a reactive weak layer buried 50-80 cm deep.
Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 3