Avalanche Forecast

Issued: Mar 22nd, 2013 10:18AM

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

triley, Avalanche Canada

Purcells.

Expect conditions to be very aspect dependant. It is Winter on Northerly aspects with dry snow and very large cornices. And it is Spring on Southerly aspects with moist snow above old crusts.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Saturday

Weather Forecast

Overnight and Saturday: Mostly clear overnight with alpine temperatures dropping down to -13.0. Light Easterly or Northeasterly winds are expected. Freezing levels rising to about 1300 metres during the day.Sunday: A ridge of High pressure will be centered over the Interior ranges bringing Light Southwest winds and daytime highs of about -6.0 in the alpine. Strong solar radiation and freezing levels rising to about 1500 metres.Monday: The ridge is expected to move Eastwards during the day, but mostly sunny conditions should continue during the day.

Avalanche Summary

Explosives control in several parts of the region resulted in some large cornice falls that released some slab avalanches in the tracks that were restricted to the recent storm snow.

Snowpack Summary

Moist snow may be found on solar aspects up to about 2000 metres. New melt/freeze crusts are developing due to cold clear nights and periods of strong solar radiation during the day. The new storm slab is about 30-50 cms deep, with wind transported pockets that are about 70 cms deep. New cornice growth is reported to be poorly bonded and breaks off easily with light triggers. A weak layer of surface hoar and/or a crust is buried down about 70-120 cms in the alpine and treeline elevations. This surface hoar layer is producing variable results in snow profile tests, and continues to be a concern for professionals.

Problems

Storm Slabs

New storm slabs may take a couple of days to settle and bond to the old surfaces. Periods of strong solar radiation may release the storm slab where it is sitting on a buried crust.

The new snow will require several days to settle and stabilize.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Extra caution needed around cornices with current conditions.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

Storm snow, wind loading or cornice fall may overload a persistent weakness buried in the upper snowpack. This could lead to surprisingly large avalanches.

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

3 - 6

Valid until: Mar 23rd, 2013 2:00PM