Avalanche Forecast

Issued: Feb 12th, 2015 7:45AM

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

Peter, Avalanche Canada

South Rockies.

Warm temperatures and sunny breaks are on the menu for Friday. Use caution in steep open terrain and around large overhanging cornices.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

Friday: Cloudy with sunny breaks. The freezing level is between 2500-3000 m. Ridge winds are light to moderate from the west. Saturday: Cloudy with possible light snow. The freezing level lowers to around 1500 m. Winds are generally light from the W-NW. Sunday: Mainly cloudy with light snow. The freezing level is around 1200-1500 m.

Avalanche Summary

Observations have been essentially non-existent in recent days. This likely speaks more to a lack of observers rather than actual conditions. I'm confident recent storm loading has produced large storm slab avalanches at higher elevations, while loose wet or wet slab avalanche activity occurred at lower elevations where rain fell.

Snowpack Summary

The rain line during recent heavy precipitation generally hovered around 1700m, although there were periods where rain fell into the alpine. Above that elevation, heavy accumulations of moist, dense snow have been pushed by strong southwest winds into much deeper deposits on the lee side of ridgecrests and terrain breaks. This recent storm snow overlies a hard crust, which may have overlying surface hoar that was buried late January. The mid-December crust/facet/surface hoar weakness may be persisting in the mid to lower snowpack at higher elevations.

Problems

Storm Slabs

Warm temperatures and sunny breaks on Friday could destabilize the recent snow resulting in natural slab or loose wet activity in steep terrain.

Be alert to conditions that change with elevation.>Choose conservative lines and watch for clues of instability.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Cornices

Warm temperatures could make large cornices unstable. Not only are they a hazard in themselves, but they could also act as a heavy trigger for large slab avalanches on the slope below.

Give cornices a wide berth when travelling on or below ridges.>Cornices become weak with daytime heating, so travel early on exposed slopes.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 4

Deep Persistent Slabs

A deeply buried week layer which formed in December should still be treated with suspicion. Not much is known about the current reactivity of this potentially destructive layer, but I'd use extra caution in steep, unsupported alpine terrain.

Be aware of the potential for very large, deep avalanches due to the presence of buried surface hoar or a facet/crust layer.>Avoid steep convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

Valid until: Feb 13th, 2015 2:00PM