Avalanche Forecast

Issued: Mar 27th, 2016 8:11AM

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

pmarshall, Avalanche Canada

Purcells.

Warming and sunshine will drive avalanche danger this week. Plan to start your day early and to avoid large sun-drenched slopes during the heat of the day.

Summary

Confidence

High

Weather Forecast

MONDAY: Cloudy with a chance of flurries early, then sunny breaks. The freezing level climbs to 1600-1800 m and winds are moderate from the N-NE. TUESDAY: Mainly sunny. The freezing level is around 2000 m and winds are light to moderate from the North. WEDNESDAY: Mainly sunny. The freezing level spikes above 2200 m. Ridge winds are generally light to moderate from the North.

Avalanche Summary

No new slab avalanches were reported on Saturday. Explosives control on Friday produced a few size 2-2.5 cornice releases, but none of these triggered slabs below. There was one report of a natural cornice fall that did trigger a size 2.5 slab, releasing at or near the ground in places.

Snowpack Summary

Thin new wind slabs have formed in exposed lee terrain in the alpine and at treeline. On solar aspects you might find a dusting of new snow on top of a melt-freeze crust. Buried persistent weak layers continue to be a concern for remote triggering in isolated areas where crusts are not strong enough to "bridge" the weakness. The late February surface hoar/crust layer is down 40-90 cm. This layer may continue to react to human triggers during periods of strong solar radiation and high daytime temperatures. Loose wet avalanches in motion, or cornice falls may step down to deeply buried weak layers. Conservative terrain without overhead hazard is a good strategy for avoiding the persistent slab problem. Cornices continue to be described as large and fragile, and may fail with forecast warming and strong sunshine this week.

Problems

Persistent Slabs

A buried persistent weakness, around 50-90 cm deep, could reactivate with strong spring sunshine and climbing temperatures this week.

Continue to seek out well supported conservative terrain as you plan your day in the mountains.>Be aware of the potential for large, deep avalanches due to the presence of a few different persistent weak layers.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Cornices

Natural cornice falls are likely during periods of strong solar radiation and warm daytime temperatures. Cornice falls may trigger deeply buried persistent weak layers.

Extra caution needed around cornices with current conditions.>Do not travel on slopes that are exposed to cornices overhead.>Cornices become weak with daytime heating. >

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

3 - 6

Valid until: Mar 28th, 2016 2:00PM