Avalanche Forecast

Issued: Feb 20th, 2013 8:00AM

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

Sylvia Forest, Parks Canada

Glacier.

Don't let the lack of natural avalanche activity fool you today. Sunny skies may lure you to the big lines - but the Feb. 12 PWL is unpredictable, and tests indicate that it is very reactive in many locations. Watch for solar warming and cornices.

Summary

Weather Forecast

A ridge of high pressure will remain over the region bringing clear skies and dry conditions. Winds will remain light from the SW, with mild temperatures. Another frontal system will move in on Thursday, bringing cloud and light flurries. The main impulse of the next system will arrive on Friday, for the weekend.

Snowpack Summary

Hard and Soft slabs overly a weak layer of surface hoar, now buried 50-60cm.� This surface hoar is best preserved and reactive between 17-1900m, and is most reactive on solar aspects where it rests on a buried sun crust.� RB scores of 2 (whole block), and wide avalanche propagations confirm that this layer is becoming more reactive as it matures.

Avalanche Summary

Natural avalanche activity is tapering off in the park, however skiers are still able to pop out slabs in the backcountry. It seems that the weak layer we are tracking now requires a specific trigger, such as a cornice fall, a skier, or even a tree bomb.

Confidence

Due to the number of field observations

Problems

Persistent Slabs

A "persistent weak layer" (Feb 12 SH) is now down 50-60 cm from the surface, and is sporadically reactive to skier triggering. Wide propagations are possible, especially on sunny aspects where it sits on a sun crust, between 17-1900m.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Wind Slabs

Wind slabs persist in lee loaded features near ridge crests and roll-overs. These have the potential to step down to the Feb 12 PWL, creating larger avalanches in specific terrain features.

Avoid lee and cross-loaded terrain near ridge crests.Give cornices a wide berth when travelling on or below ridges.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Feb 21st, 2013 8:00AM