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Archived

Avalanche Forecast

Mar 11th, 2013–Mar 12th, 2013
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
2: Moderate
The avalanche danger rating below treeline will be moderate
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: South Coast.

The avalanche danger will rise throughout the day on Tuesday as snow accumulates, winds increase, and the freezing level rises.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain for the entire period

Weather Forecast

Synopsis: A steady southwest flow will drive a series of disturbances onto the south coast this week. There is some uncertainty regarding the timing of each pulse of heavier precipitation, but it’s fairly certain to be a wet and mild week. Overnight and Tuesday: Moderate precipitation – 10-20 cm. The freezing level will rise to around 1500 m by Tuesday afternoon. Winds are strong from the south-southwest. Wednesday: Moderate to locally heavy precipitation – 15-20 cm. The freezing level climbs to 1800 m. Winds remain strong from the south-southwest.  Thursday: Moderate precipitation continues. The freezing level starts near 1600 m but could drop later in the day or by Friday morning.  

Avalanche Summary

Thin wind slabs to size 1.5 were skier triggered on steep north facing slopes on Saturday and Sunday. They were reported to have released on surface hoar buried on March 9th. There was a report of a size 2 skier triggered slab avalanche on a steep southwest apsect in the Steep Creek area (Duffey Lake). This incident happened a few days ago, but highlights the lingering potential for triggering large slab avalanches.

Snowpack Summary

A dusting of new snow overlies a variety of old surfaces which include: a crust at lower elevations and on solar aspects, faceted powder on shaded slopes, and surface hoar. The surface hoar, which was reported from the north of the region, has already been reported to be reactive where it was buried by wind slabs formed by strong southwest winds on Saturday.Between 50 and 80cm below the surface is a layer surface hoar which was buried on February 20th. Triggering this layer has become difficult, but heavy snow or rain this week could be enough new load to awaken this layer in specific areas. Below this the snowpack is generally well settled and strong.

Avalanche Problems

Storm Slabs

New snow may not bond well to the previous snow surface, which includes surface hoar, a sun crust, and older wind slabs. Expect the new snow to be most touchy where it is deposited into dense wind slabs in exposed north through east facing terrain.
Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Be cautious as you transition into wind affected terrain.>Choose conservative lines and watch for clues of instability.>Avoid exposure to overhead avalanche terrain, as large avalanches may reach the end of runout zones.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 4