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Archived

Avalanche Forecast

Feb 27th, 2017–Feb 28th, 2017
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
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
3: Considerable
The avalanche danger rating at treeline will be considerable
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
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Northwest Coastal.

Fresh and reactive storm slabs will build over the forecast period. Rider triggers are likely, especially where buried surface hoar exists or on leeward slopes that have thicker slabs due to wind loading.

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

A change in the weather pattern is upon us as the upper jet shifts to a westerly flow allowing a series of Pacific frontal systems to track across the Coastal Regions.Tuesday: Snow 10-25 cm with heavier amounts being more coastal. Alpine temperatures near -6 and ridgetop winds moderate-strong from the SW. Wednesday: Cloudy with snow amounts 5-15 cm. Alpine temperatures near -8 and ridgetop winds moderate with strong gusts from the SW.Thursday: Snow amounts  5-15 cm. Alpine temperatures high of -3 accompanied by gusty (90 km/hr) ridgetop winds. Freezing levels rising to 700 m.

Avalanche Summary

On Sunday no new natural avalanche activity was reported, however; several skier triggered wind slabs up to size 1.5 were triggered in alpine elevations.  Changing wind directions and new storm snow will likely develop new wind slabs in the alpine.

Snowpack Summary

A recent addition of up to 10 cm of new snow has not dramatically changed the snowpack structure, but Saturday night's storm buried a new layer of surface hoar which will get buried deeper after tomorrows snowfall. At this time it is unknown how well preserved this surface hoar. A variety of surface conditions exist including isolated wind slabs, pockets of soft snow (15 to 25 cm deep), sun crusts, and surface hoar. A supportive rain crust exists below 1000 m. A layer of surface hoar that was buried on February 10th can be found buried 30 to 60 cm deep at tree line elevations and has been reactive in some recent snowpack tests. Below this layer, the snowpack is generally settled and strong. The exception is shallow snowpack areas around Bear Pass and Ningunsaw where basal facets remain an ongoing concern.

Avalanche Problems

Storm Slabs

New storm slabs will build with forecast snow and wind. They may be more reactive on leeward slopes that see deeper deposits due to wind loading. The new storm slabs may also be more reactive in locations where buried surface hoar exists.
Use caution in lee areas. Wind loading could create slabs.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.Minimize exposure to avalanche terrain during periods of heavy loading from new snow, wind, or rain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 2