Avalanche Forecast

Issued: Mar 19th, 2013 8:03AM

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

Parks Canada Sylvia Forest, Parks Canada

The main concern today is storm snow slabbing up.  Sunny skies and strong solar radiation could result in increased avalanche activity.  Tomorrow a strong system is expected to bring more snow and loading to the area.

Summary

Weather Forecast

An upper ridge will build over the province today, bringing dry but windy conditions.  Freezing levels will rise to 1500m, and solar radiation will become a factor.  Another low will move into the area on Wednesday bringing moderate to heavy precipitation and strong SW winds.

Snowpack Summary

Intense but intermittent flurries yesterday with locally very strong winds has added more load to the snowpack.  Up to 35 cm of snow is beginning to slab up, especially in the alpine.  Below 2000 meters, this storm snow sits on a sun crust formed on March 16.  The mid-pack remains well settled.  The Feb 12 PWL can still be found, but is stubborn.

Avalanche Summary

Numerous new slab avalanches were noted yesterday, associated with the new storm snow and strong winds, in the alpine and treeline.  Several skier triggered avalanches were triggered in the Hermit area two days ago to size 1.0. These were low density slabs sliding on a crust down 15cm with surprisingly wide propagation running far and fast.

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Wednesday

Problems

Storm Slabs

An icon showing Storm Slabs
Convective snow flurries with strong winds yesterday added load to the storm slab problem above treeline. Below 2000 meters, a buried rain crust is providing an ideal bed surface for new snow avalanches at lower elevations.
Avoid lee and cross-loaded terrain near ridge crests.Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Wind Slabs

An icon showing Wind Slabs
Moderate south winds and new snow available for transport mean that you could expect windslabs on lee terrain above treeline.  Cornices are growing larger.
Avoid lee and cross-loaded terrain near ridge crests.Pay attention to overhead hazards like cornices.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
It will likely take a large trigger, like a cornice or another avalanche to trigger the surface hoar/crust layer from February 12, now down 1-1.5m. The resulting avalanche would be very large and destructive if triggered.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

3 - 4

Valid until: Mar 20th, 2013 8:00AM