Avalanche Forecast

Issued: Mar 2nd, 2013 10:16AM

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

ghelgeson, Avalanche Canada

Cariboos.

The storm may be over, but the mountains are currently primed for skier/sledder triggered avalanches.

Summary

Confidence

Fair

Weather Forecast

Synopsis: The pineapple express will continue to deliver moisture laden air and significant precipitation through Saturday night before things begin to dry out on Sunday/MondaySaturday Night: 10/15 cm/mm snow/rain. Freezing level around 1400 at Sunset, steadily lowering through the night. Moderate to Strong SW winds.Sunday: Freezing level starts at 450m rising to 900m during the day. No precipitation expected. Cloudy skies. Winds switch to the NE, mod at treeline, strong at ridge top. Monday: Freezing level at valley bottom. No preicp. Clear skies. Winds light and variable.Tuesday: Freezing level at valley bottom, rising to 500m during the day. No significant precip. Cloudy skies. Winds become more organized out of the south as another deep upper low approaches the province.

Avalanche Summary

Visibility has been limited, as a result we don't have much in the way of avalanche observations from Friday. On Thursday, natural avalanches up to size 3.5 were observed on north and south aspects from 1500 m to 2200 m.

Snowpack Summary

This latest storm is really packing a punch, it's laid down around a meter of snow at this point, much of which is heavy and moist. The snow surface became wet as snow gradually turned to rain to approximately 1800 m in the south of the region and 1500 m in the north. I expect a crust to develop at lower elevations as temperatures drop Saturday night. Strong southwest winds have redistributed the new snow into deep wind slabs on exposed lee slopes and cross-loaded gully features. The February 12 persistent weak layer (crust, and/or surface hoar) is now down 60-100 cm. It is primed for triggering and has been reacting readily to both natural and human triggers on all aspects and a wide range of elevations. Deeper persistent weak layers from early February and late January continue to show planar failures when moderate to hard forces are applied in snow pack tests. These deeper layers have not been reactive to the weight of a rider, but they could potentially be triggered during or immediately after the present storm system, further increasing the potential size of avalanche events.

Problems

Storm Slabs

Natural activity should taper off Sunday, but conditions remain primed for human triggering due to to the presence of a deeply buried weak layer.

Avoid exposure to overhead avalanche terrain, as large avalanches may reach the end of runout zones.>Avoid paths that have not avalanched recently.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

3 - 7

Persistent Slabs

Additional loading from snow and wind, or the weight of a rider could be enough to trigger the February 12 persistent weak layer.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

3 - 7

Cornices

The storm has left many large cornices in it's wake on lee slopes, many of which are teetering on the brink of failure. Cornice fall has the potential to initiate large destructive avalanches.

Do not travel on slopes that are exposed to cornices overhead.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Valid until: Mar 3rd, 2013 2:00PM