Avalanche Forecast

Issued: Mar 25th, 2016 9:06AM

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.

triley, Avalanche Canada

Purcells.

Special Public Avalanche Warning in effect for this region for the Easter Long Weekend.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain on Saturday

Weather Forecast

Mostly clear overnight with light westerly winds and freezing down to valley bottoms. On Saturday, a mix of sun and high cloud with light southwest winds and freezing levels rising to 1700 metres. Cloud and light precipitation developing by Sunday morning with freezing down to at least 1000 metres. On Sunday, cloudy with 3-5 cm of snow and freezing levels rising up to 1300 metres. Light snow and light winds continuing on Monday, before the next ridge of high pressure brings back the clear skies.

Avalanche Summary

No new slab avalanches reported. One natural cornice fall on Friday released size 2.5 and gouged to ground in some parts of the runout. We had a report on Monday of a skier remote triggered avalanche size 2.5 from 200 metres away on a southeast aspect at 2320 metres, believed to have released on the February 27th weak layer. I suspect that warming and strong solar have resulted in loose wet avalanches in steep alpine and treeline terrain. Natural cornice falls are expected during the melt period of the melt-freeze cycle.

Snowpack Summary

Thin new wind slabs have formed in the alpine and at treeline. Cornices continue to be described as large and fragile, and may fail with additional loading from forecast snow, or from high daytime temperatures. 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 weak 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.

Problems

Persistent Slabs

Sudden planar results in snowpack tests suggest that triggering this layer may result in wide fracture propagations and large avalanches. Avoid convex un-supported terrain features.

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

Likely

Expected Size

3 - 5

Loose Wet

Loose wet avalanches may release naturally from steep sun exposed slopes. Heavy moist or wet snow can pile up and push you into a terrain trap.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Mar 26th, 2016 2:00PM