Avalanche Forecast

Issued: Mar 16th, 2013 10:12AM

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

jlammers, Avalanche Canada

South Columbia.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Sunday

Weather Forecast

Saturday night and Sunday: Moderate snowfall becoming light on Sunday / Moderate southwest winds becoming light and northwesterly with strong gusts / Freezing level at 800mMonday: Light snowfall / Light west winds with strong gusts / Freezing level at 700mTuesday: A mix of sun and cloud with snowfall developing late in the day / Light southwest winds / Freezing level at 1200m

Avalanche Summary

A widespread natural slab avalanche cycle to size 3.5 was reported on Thursday and Friday.Â Avalanche activity occurred on all aspects and elevations. At lower elevations where rain fell, wet slabs and full-depth glide crack releases were observed. At higher elevations, activity occurred within the recent storm snow, or at the March 10th surface hoar interface.

Snowpack Summary

At treeline and above, light amounts of new snow overlie deep and cohesive storm slabs that formed with heavy snowfall, strong southwest winds and warm temperatures. Widespread cornice development has also taken place. At lower elevations rain penetrated the snowpack, and below 1400m the snowpack was reported to be isothermal. The recent storm snow overlies a weak layer of surface hoar or a sun crust that were buried on March 10th. Some areas had strong winds before the surface hoar was buried, so its distribution may be specific to sheltered and shaded terrain features. Some professionals are still expressing concern for the layer of surface hoar buried on February 12th. This interface is now well over 1.5m below the surface and triggering has become unlikely.

Problems

Storm Slabs

New snow accumulations are forecast to add load to an existing storm slab problem which has produced destructive avalanches in recent days. Expect increased reactivity in wind-affected terrain or in areas where buried surface hoar exists.

Be wary of slopes that did not previously avalanche - even on low angle terrain.>Avoid exposure to cornices and overhead avalanche terrain, as large avalanches may reach the end of runout zones.>Be alert to conditions that change with elevation.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 6

Cornices

Recent stormy weather has formed large and potentially weak cornices. Cornice falls may be highly destructive, and could also trigger large avalanches on the slope below.

Extra caution needed around cornices with current conditions.>Pay attention to overhead hazards like cornices.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 6

Valid until: Mar 17th, 2013 2:00PM