Avalanche Forecast

Issued: Mar 28th, 2016 8:29AM

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

pmarshall, Avalanche Canada

Purcells.

Expect avalanche danger to rise during the day, particularly on sun-exposed slopes. Plan to start your day early and move away from large sun-drenched slopes during the heat of the day.

Summary

Confidence

Moderate

Weather Forecast

WEATHER SUMMARY: It will be a sunny and warm week! Temperatures will steadily climb each day with the freezing level reaching at least 2500 m by Thursday (treeline temps near +5). Ridge winds should be generally light from the NW-NE.

Avalanche Summary

There was one report of a size 2 natural cornice fall on Sunday that did not trigger a slab below. No new slab avalanches were reported on Saturday or Sunday. 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 on Friday 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. Southerly aspects should go through a daily melt-freeze cycle throughout the week. 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. Cornices continue to be described as large and fragile, and may fail with forecast warming and strong sunshine this week. Conservative terrain without overhead hazard is a good strategy for avoiding the persistent slab problem.

Problems

Persistent Slabs

Intense spring sun and rising temperatures could reactivate buried persistent weaknesses in the upper snowpack.

Be aware of the potential for large, deep avalanches due to the presence of a few different persistent weak layers.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Cornices

Tread cautiously near large overhanging cornices. Weak cornices could pop off naturally, potentially triggering large slabs on the underlying slope.

Cornices become weak with daytime heating. >Do not travel on slopes that are exposed to cornices overhead.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

3 - 6

Loose Wet

Expect loose wet slides on steep sunny slopes in the afternoon. A wet sluff in motion could trigger deeper weaknesses creating large destructive slabs.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

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

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Mar 29th, 2016 2:00PM