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Avalanche Forecast

Mar 11th, 2013–Mar 12th, 2013
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
1: Low
The avalanche danger rating below treeline will be low
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
1: Low
The avalanche danger rating below treeline will be low
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.

The current storm track has the bulk of the incoming precipitation hitting the South and Central Coast. If the track slides a little further north we could see much more snow and higher avalanche danger.

Confidence

Poor - Track of incoming weather is uncertain for the entire period

Weather Forecast

Synopsis: A steady southwest flow will drive a series of disturbances onto the BC coast this week. There is some uncertainty regarding the track timing of each pulse of heavy precipitation. Currently it looks like Terrace and south will see decent precip amounts, but northern areas may be considerably drier. Tuesday: 5-10 cm. The freezing level is around 500 m. Winds are moderate to strong from the southwest. Wednesday: 5-10 cm. The freezing level is steady around 500 m and winds increase to strong from the southwest. Thursday: Moderate to locally heavy snow. The freezing level should rise to 1000-1200 m.

Avalanche Summary

Several natural size 1-2 wind slabs were observed out of exposed north and east aspects. There was also a report of a remotely triggered size 2 hard wind slab from an exposed NE aspect at treeline. This slide most likely failed on the recently buried surface hoar layer.

Snowpack Summary

Light to locally moderate amounts of new snow now overlie a variety of old surfaces which include: a crust at lower elevations and on solar aspects; old wind slabs in exposed areas, and fairly widespread large surface hoar. Moderate to locally extreme west/southwest winds have redistributed the new snow into soft and hard wind slabs in exposed terrain. I would expect the new snow to be quite reactive, especially where it overlies the surface hoar which was buried on March 9th. This interface is likely to be one to watch as the overlying slab develops.The mid snowpack layers are generally well settled and strong. Facets at the base of the snowpack may resurface as a concern now that spring warming is on the doorstep and full-depth releases are becoming more likely (primarily in the northern part of the region).

Avalanche Problems

Wind Slabs

Light snow and strong winds have created new wind slabs in exposed terrain. Wind slabs may be particularly reactive in areas where they overlie a weak layer of buried surface hoar.
Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>Choose well supported terrain without convexities.>

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 4