Avalanche Forecast

Issued: Jan 10th, 2014 9:18AM

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.

slemieux, Avalanche Canada

South Rockies.

Summary

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Tonight and Saturday: A strong low pressure system will track over the province tonight leaving moderate to heavy precipitation on the region tonight and tomorrow. Around 20-30 mm in water equivalent is forecasted. This will be accompanied by strong winds from the SW during the night and during the day tomorrow. Freezing levels are expected to rise to 1500 m tonight and lower to 1100 m tomorrow. Sunday: Another system is tracking through the province but is not expected to leaving light amounts of precipitation over the region. Moderate W winds should increase in speed during the day. Freezing levels are forecasted to rise back up but there is some disagreement between models.Monday: Light to moderate precipitation as a cold front moves across the interior with similar freezing levels.

Avalanche Summary

Multiple natural and skier triggered loose dry avalanches and slab avalanches up to size 1 were reported yesterday.

Snowpack Summary

The significant amounts of snow forecasted tonight and tomorrow, the strong SW winds redistributing this snow and warmer temperatures is increasing the avalanche danger for tomorrow. Windslabs lee of SW winds below ridgetop in the alpine and at treeline will be very touchy and the storm snow in sheltered areas will also need time to settle. Cornices will continue building and could fall with this additional load. Yesterday's 10-20 cm created some windslabs in the alpine lee of W-SW winds which could be hidden by the new snow that will fall tonight and tomorrow. When tested and observed, the surface hoar layer down 70 cm is showing signs of healing (grains are rounding and snowpack tests are not as planar as they have been previously).The facet/crust layer down 80-100 cm at treeline has been mostly reactive on E aspects and the depth hoar layer in the alpine is still concern especially where the snowpack is thinner.

Problems

Storm Slabs

New snow and wind loading will most likely create instabilities in the snowpack: Windslabs in the alpine and treeline lee of SW winds, sluffing in steeper terrain and possibly storm slab at all elevation and on all aspects.

The new snow will require several days to settle and stabilize.>Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Avoid avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

The forecasted load could awaken the deeper instabilities located down a meter and at the bottom of the snowpack.

Be aware of the potential for large, deep avalanches due to the presence of buried facet/crust layer and depth hoar layer.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Jan 11th, 2014 2:00PM