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Archived

Avalanche Forecast

Feb 25th, 2013–Feb 26th, 2013
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
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
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Northwest Coastal.

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Synopsis: A frontal system will hit the coast early on Tuesday spreading moderate snow and increasing winds. This is followed closely by a second system late Wednesday.  Tuesday: Light to moderate snowfall – 10-15 cm. The freezing level is around 600 m and winds increase to very strong from the south-southeast. Wednesday: Unsettled with light snow during the day and heavier snow in the evening (~15 cm). The freezing level is steady near 600-700 m and winds remain strong from the south-southwest. Thursday: Moderate to locally heavy snow. The freezing level climbs closer to 1000 m.

Avalanche Summary

Better weather on Sunday allowed for more observations of a fairly widespread natural avalanche cycle in higher alpine terrain. Slabs were reported to be size 2-3 and were primarily from wind loaded features. On Sunday, the storm and wind slabs were still reactive to ski cuts to size 1.5 and explosive control to size 3. Loose moist avalanches were also observed on steep southerly aspects when the sun came out.

Snowpack Summary

Mild temperatures have promoted rapid settlement of the recent storm snow. Strong southwest winds also created deep and weak wind slabs in exposed lee terrain and cross-loaded gully features. This new snow fell on a crust, old wind slab, and/or surface hoar depending on aspect and elevation. One recent snowpack test near Shames resulted in a hard "pops" shear on the buried surface hoar, down around 60 cm at the time. Most areas are reporting that the snow has bonded well to the underlying melt-freeze crust. Cornices that now loom over many features may become weak with continued growth and/or daytime warming. The mid and lower snowpack layers are generally well settled and strong. The exception seems to be the Bear Pass area where basal facets are still reported.

Avalanche Problems

Wind Slabs

It may be possible to trigger deep storm slabs in steep terrain, particularly in exposed lee and cross-loaded features (north through east facing slopes).
Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.>

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 5

Cornices

Cornices have grown large and weak and may pop off with continued growth or during periods of mild sunny weather.
Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 2 - 5