Avalanche Forecast

Issued: Mar 20th, 2013 10:54AM

The alpine rating is high, 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

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

Overnight and Thursday: Winds becoming Westerly moderate to strong overnight as the snow continues to fall across the region. Expect another 5-15 cms overnight and another 5 cms during the day. Alpine temperatures should drop down to near -10.0, and the freezing level should be at valley bottoms.Friday: Unsettled weather with mostly cloudy skies and strong to very strong gusty Northwest winds. Continued cool temperatures in the alpine and freezing levels rising to about 1000 metres during the day.Saturday: A ridge of High pressure is moving into the region bringing light West winds, clearing skies, and alpine temperatures in the -10.0 - -15.0 range.

Avalanche Summary

A couple of natural cornice falls were reported size 3.0 that released old storm snow slabs from the sloped below. Some skier controlled pockets of wind transported snow were reported up to size 1.5

Snowpack Summary

Strong winds and new snow have developed new storm slabs on all aspects and at all elevations. Wind transported snow has created thick pockets of wind slab in the lee of alpine winds. New cornice growth may be extensive and weak, causing natural cornice falls. Buried sun crusts on Southerly aspects continue to produce planar fractures in snow profile tests down about 80-100 cms. Large avalanches releasing on the March 10th weak layer are still a concern.

Problems

Storm Slabs

An icon showing Storm Slabs
New storm slabs continue to develop due to new snow and strong winds. Deep pockets of wind transported snow continue to develop at higher elevations. It may take several days for the new snow to settle and bond.
The new snow will require several days to settle and stabilize.>Avoid freshly wind loaded features.>Extra caution needed around cornices with current conditions.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
The new load of storm snow may trigger the buried weak layer of surface hoar from March 10th that is now down about 100 cms. Large loads like cornice fall are expected to continue to trigger this layer.
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 6

Valid until: Mar 21st, 2013 2:00PM