Avalanche Forecast

Issued: Mar 5th, 2013 9:49AM

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

swerner, Avalanche Canada

Kootenay Boundary.

Summary

Confidence

Good

Weather Forecast

Tonight and Wednesday: A low pressure system moves inland to the South of the border. Light-moderate precipitation will begin this evening over the Southern ranges. Ridgetop winds light from the SE. Alpine temperatures near -5 and freezing levels 1300 m. Thursday: Mainly cool and dry with some clouds. Ridgetop winds light from the NW. Alpine temperatures near -7 and freezing levels at 1200 m. Friday: The ridge will remain over the region with mainly dry, sunny conditions. Ridgetop winds light from the NW. Alpine temperatures near -7 and freezing levels at 1300 m.

Avalanche Summary

On Monday, natural slab avalanche activity occurred up to size 2 on N-E aspects and above 2000 m. Numerous natural loose dry avalanches also occurred up to size 1.0 from steeper terrain features.

Snowpack Summary

In much of the region, up to 80 cm recent snow overlies older interfaces comprising of surface hoar and sun crusts. The storm slab above these interfaces has the potential for wide propagations and surprisingly large avalanches.Wind slabs and new cornice development exist at ridgelines and on lee slopes. These are likely sensitive to human triggers. A strong melt-freeze crust exists at 1700 m and below and is generally bridging any deeper instabilities. The average treeline snow depths sit near 250 cm.

Problems

Wind Slabs

Recent snow and wind have formed touchy wind slabs on all aspects. Rider triggering is likely, especially on lee slopes that have been wind loaded.

Avoid lee and cross-loaded terrain near ridge crests.>Be alert to conditions that change with elevation.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

The presence of weak layers buried in the upper snowpack means there is a risk of triggering surprisingly large slab avalanches.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 6

Valid until: Mar 6th, 2013 2:00PM