Avalanche Forecast

Issued: Mar 11th, 2013 10:33AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs and Persistent Slabs.

Avalanche Canada triley, Avalanche Canada

A warm and wet storm is developing. Strong winds, a heavy storm load, and rising temperatures are increasing the avalanche danger.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Tuesday

Weather Forecast

Overnight and Tuesday:  A warm front is forecast to move into the interior overnight bringing cloud and strong Westerly winds. Moderate snow fall amounts are expected to begin by early morning and become heavy during the day. Freezing levels are expected to rise to about 1200 metres.Wednesday:  Continued warm and wet. Moderate to heavy precipitation with strong Westerly winds and freezing levels rising to about 1500 metres.Thursday: Unsettled weather with continued light to moderate precipitation and moderate Westerly winds.

Avalanche Summary

Some thin new pockets of wind slab were released from ski cutting or accidentally while skiing. There was one report of a size 2.5 natural slab avalanche on a West aspect in the Selkirks at 2200 metres. This avalanche was interesting because it failed on a planar slope that had previously released from higher on the slope during the last storm. I expect that the new storm will continue to trigger the deep weak February 12th layer in isolated areas with the right combination of preserved surface hoar, old sun crusts, where no avalanches released after the last storm.

Snowpack Summary

New wind slabs are developing above a new surface hoar layer on shaded aspects and a sun crust on solar aspects. The weak layer of surface hoar that was buried on February 12th is now down about 100-150 cm and was not triggered by cornice falls over the weekend. Some areas report that the February 12th surface hoar is rounding and getting harder to shear in snow profile tests, but continues to give planar shears when it does fail. Avalanches failing on the February 12th layer have become a low probability/ high consequence situation.

Problems

Storm Slabs

An icon showing Storm Slabs
A new storm slab is expected to develop due to forecast new snow and wind. This new storm slab may be sitting on a weak layer of surface hoar that developed during the recent clear weather.
The new snow will require several days to settle and stabilize.>Avoid freshly wind loaded features.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 5

Persistent Slabs

An icon showing Persistent Slabs
A weak layer of buried surface hoar down about 100-150 cm may be triggered by the load of new storm snow and wind.
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

4 - 7

Valid until: Mar 12th, 2013 2:00PM

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