Avalanche Forecast

Issued: Apr 9th, 2013 10:24AM

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

pgoddard, Avalanche Canada

Purcells.

Avalanche danger will vary from place to place depending on local snowfall amounts and freezing levels. The heaviest precipitation is expected in the west.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain for the entire period

Weather Forecast

Tuesday night/ Wednesday: 10-30 cm snow. Strong to extreme W winds. Freezing level around 1500 m overnight, rising to near 2000 m in the south (~1700 m in the north). Thursday: Light snow. Moderate to strong NW winds. Freezing level around 1600 m. Friday: Light snow. Light S winds. Freezing level around 1500 m.

Avalanche Summary

An avalanche cycle of slabs up to size 3 occurred during last weekendâ€™s storm. Many of these events were on NE-NW aspects above about 2400 m. Several size 2 skier-remote triggered slabs were also reported on Sunday. These failed on surface hoar buried below the storm snow. They occurred on W-NE aspects above 2500 m. Little activity was reported on Monday.

Snowpack Summary

Up to 50 cm recent storm snow is sitting on a variable interface, consisting of a crust, moist snow, surface hoar or facets. The surface hoar or facet interface is mainly found on high-elevation northerly aspects. It has recently been very touchy, with remote skier-triggering occurring. Forecast precipitation will add to this storm slab problem and create new wind slabs at high elevations, and weaken the snowpack with rain at low elevations. Large cornices are likely to increase in size and become more prone to failure during Wednesdayâ€™s storm.

Problems

Storm Slabs

New snow and wind will create new storm slabs at high elevations, which may overload a weakness buried in the upper snowpack, creating large avalanches.

Avoid exposure to avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Avoid steep slopes below cornices.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 5

Loose Wet

Loose wet avalanches and glide slabs may fail naturally in response to rainfall at low elevations.

Watch for wet loose or slab activity with forecast rain and/or warm temperatures.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Valid until: Apr 10th, 2013 2:00PM