Avalanche Forecast

Issued: Apr 10th, 2015 10:30AM

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

ghelgeson, Avalanche Canada

Purcells.

If alpine storm snow totals exceed 10cm, the alpine danger rating will likely rise to Considerable.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

FRIDAY NIGHT: 1 to 2mm of precipitation possible, less than 5cm total snowfall expected. Strong SW winds.SATURDAY: Freezing level hovering around 1500m. Moderate SW winds at treeline, Strong SW/W winds at ridgetop. 2 to 3mm precipitation, 2 to 6cm of snow possible. Overcast.SUNDAY: Freezing level starting at 1000m rising to 1500m. Light SW winds at treeline, Moderate W winds at ridgetop. Scattered cloud. Isolated flurries, no significant precipitation expected.MONDAY: Freezing level around 1500m. Light SW winds at treeline, moderate SW winds at ridgetop. Few clouds in the morning building to overcast in the afternoon. Scattered afternoon flurries, no significant precipitation expected.

Avalanche Summary

Several cornice falls have been reported in the last few days, some of which have triggered slabs on slopes below, some which have not.

Snowpack Summary

Surface faceting is beginning to work on the 10 to 25cm cm generated by convective snow fall last weekend. The atmosphere has been unusually calm and wind effect is very isolated. This snow remains dry on north facing features above 2300m while corn is starting to form to ridge-top on south facing aspects. Moist snow is reported everywhere else. Just below this snow you will likely find the the late-March crust which is supportive to around 2000m. Moist snow underneath the late-March crust is ubiquitous in most of the region.Persistent weak layers in the mid-pack remain a lingering concern, although they seem to have gone dormant for the time being. In the north of the region, the mid-March crust/facet layer is down 40-60cm and the mid-February crust/facet/surface hoar layer is down about 80 cm. While weak layers formed earlier in the winter remain intact, they too are dormant at this time.

Problems

Wind Slabs

A relatively small amount of snow Friday night and Saturday accompanied by strong SW winds will likely result in the development of thin fresh wind slabs. These slabs are expected to be most sensitive immediately lee of ridge-crest.

Use ridges or ribs to avoid pockets of wind loaded snow.>Avoid freshly wind loaded features.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Cornices

Increased winds Friday night and Saturday will add to the already large cornices that loom over many features, potentially increasing the likelihood of failure. Cornice failure has the potential to release slabs on slopes below.

Extra caution needed on slopes that are exposed to cornices overhead.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 5

Valid until: Apr 11th, 2015 2:00PM