Avalanche Forecast

Issued: Jan 11th, 2014 9:35AM

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

Avalanche Canada slemieux, Avalanche Canada

Strong winds from the West are expected to keep loading lee slopes tomorrow and possibly trigger large avalanches.

Summary

Confidence

Fair - Freezing levels are uncertain on Tuesday

Weather Forecast

Tonight and Sunday: The tail of the system exiting is expected to leave more precipitation tonight. Light to moderate amounts are forecasted for tonight (10 mm in water equivalent) and none during the day tomorrow with strong winds from the W. Freezing levels should fall to valley bottom tonight. There could be some clearings in the morning tomorrow. Monday: Another warm front is pushing in bringing light to moderate amount of precipitation during the night between Sunday and Monday, strong Westerlies and freezing levels rising to 1800 m. Tuesday: A ridge building over the regions should bring dryer and warm temperatures.

Avalanche Summary

A natural avalanche cycle happened today with the new snow and warming up of temperatures. Several natural avalanches up to size 2.5 occurred yesterday and today on all elevation and all aspect. Yesterday, multiple skier triggered avalanches up to size 1.5 were also reported yesterday in the storm snow on E and NE aspects. Yesterday, explosive control in the southern part and central part of the region produced up to size 2.5 avalanches on SE and SW aspects that propagated quite wide.

Snowpack Summary

Windloading lee of strong westerly winds in the alpine and at treeline will keep avalanche conditions dangerous tomorrow.  The new windslabs will most likely be very touchy and could possibly be triggered naturally. The ~30 cm of snow from the last storm is expected to have to potential to sluff in steep sheltered terrain.  Under the new snow, a surface hoar layer is sitting on a sun crust on S facing aspects in some locations and could be buried around 40 cm. The persistent weak layers (PWL) are a concern to avalanche professionals as they have been producing sudden planar results and show good propagation potential when tested in the last week. The end of November facet/crust or surface hoar layer down 90 cm (or 50 cm where snowpack is very thin) and the depth hoar or basal facetting are the most worrisome layers. The additional load from the strong winds tomorrow could make them reactive again.

Problems

Storm Slabs

An icon showing Storm Slabs
Windslabs will keep developing lee of strong W winds and is be the main concern for tomorrow. Beware of the possibility of sluffing in steep sheltered terrain and of storm instabilities that could linger.
Be cautious as you transition into wind affected terrain.>Avoid avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Travel on ridgetops to avoid wind slabs on slopes below.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
Deep persistent instabilities could still be lingering in the snowpack and be triggered by a large load such as the windloading that is forecasted.
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar, facet/crust and depth hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Jan 12th, 2014 2:00PM