Avalanche Forecast

Issued: Nov 23rd, 2015 8:36AM

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

Avalanche Canada swerner, Avalanche Canada

Avalanche hazard is on the rise with new snow and wind. Given the very limited information on hand to create this bulletin, I would tread cautiously and take the time to gather snowpack information as I go. Check out the MIN, give and get info!

Summary

Confidence

Poor - Due to the number and quality of field observations

Weather Forecast

The first arctic outbreak of the season brings outflow winds, modified cold air and additional snow falling to valley bottom through Tuesday. A blocking high pressure system will likely keep things cold and dry through the forecast period.Monday night/ Tuesday: New snow 10-20 cm overnight. Ridgetop winds blowing moderate from the N-NE and temperatures at treeline elevations hovering around -10.0.Wednesday/ Thursday: Freezing levels will remain at valley bottom with average treeline temperatures near -7.0. Light winds will continue from the N-NE direction

Avalanche Summary

On Monday, numerous skier controlled storm slabs up to size 1 were reported. With continued snow and wind throughout the day and overnight I suspect a natural avalanche cycle is happening as I write this. The new storm snow will need some time to settle out and adjust to the old snow surfaces. New snow, wind, weak layers and direct action avalanches are obvious indications for avalanche hazard to rise. However, the tricky part may be yet to come, when this storm settles out and people are chomping at the bit to get out. Rider triggered avalanches are still likely, and it's the deeper, early season persistent weak layers in which most of my uncertainty lies.

Snowpack Summary

New storm snow amounts range from 15-25 cm. Initially, the storm arrived with strong southwest winds leaving lee slopes with deeper deposits. This new snow will likely have a poor bond to the old surfaces that comprise of surface hoar, crusts (potentially up to 2100 m) and some dry facetted snow above that. Forecast changing winds (outflow from the north) will likely redistribute the new snow on opposite slopes possibly building wind slabs that could catch you by surprise. Snowpack depths are highly variable across the region; however, slopes below treeline are below threshold for avalanche activity. Where the near-surface crust is robust (>1cm thick), the upper snowpack has gained strength and avalanches failing on deeper layers have become much less likely. I'd be extra cautious in areas where the near-surface crust is thin or has not formed (I'm thinking high alpine terrain or northern parts of the region).

Problems

Storm Slabs

An icon showing Storm Slabs
New storm slabs continue to build and may have a poor bond to the old snow. Natural avalanches are likely. Changing winds will redistribute new snow adding complexity to the avalanche problem, touchy wind slabs may exist on all aspects.
The recent storm snow may take several days to settle out. Stick to mellow slopes and use a cautious approach to terrain while gathering information along the way.>Stay off recent wind loaded areas.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Valid until: Nov 24th, 2015 2:00PM