Avalanche Forecast

Issued: Apr 11th, 2015 8:39AM

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

ghelgeson, Avalanche Canada

Purcells.

While it feels like spring in the valley, the alpine has returned to winter. Stay on your toes as a potentially touchy storm/wind slab likely exists at upper elevations.

Summary

Confidence

Fair

Weather Forecast

SUNDAY: Freezing level starting at 1000m rising to 1700m. Light W/SW winds at treeline, Moderate W winds at ridge-crest. Scattered cloud. Isolated flurries, no significant precipitation expected.MONDAY: Freezing level starting around 1300m, rising to 2000m. Light SW winds at treeline, moderate SW winds at ridge-crest. Few clouds in the morning building to overcast in the afternoon. Scattered afternoon flurries with 2 to 10cm of snow possible Monday night.TUESDAY: Freezing level around 1400m. Light W/NW winds at treeline, moderate NW winds at ridge-crest. 1 to 5cm of snow possible during the day. Broken cloud cover.

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

The region picked up around 5 to 15cm of snow Friday night accompanied by strong SW winds burying the old surface which consists of facets, surface hoar and crust. Prior to Friday nights storm the 10 to 25cm that fell the weekend of April 4th remained dry on north facing features above 2300m while corn was starting to form to ridge top on south facing aspects. East and west facing features had turned moist.Down 15 to 40cm you will find the supportive late-March crust that is thought to exist up to around 2100m. 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 45 to 75cm and the mid-February crust/facet/surface hoar layer is down 80 to 90cm. While weak layers formed earlier in the winter remain intact, they too are dormant at this time.

Problems

Storm Slabs

Snowfall Friday night was accompanied by strong SW winds, and these winds are expected to continue into Sunday. Fresh storm/wind slabs are sitting on crust, facets and/or surface hoar which may keep them touchy into early next week.

Wind slabs are likely most problematic immediately lee of ridge-crest. Use ridges or ribs to avoid pockets of wind loaded snow.>Avoid freshly wind loaded features.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Cornices

Ongoing winds are adding to the already large cornices that loom over many features, possibly increasing the likelihood of failure. A large cornice failure may be able to trigger a slab release on slopes below.

Be aware of the potential for cornice fall to trigger surprisingly deep slabs.>Extra caution needed on slopes that are exposed to cornices overhead.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

2 - 5

Loose Wet

There is potential for an active loose wet cycle Sunday as clouds begin to breakup while the freezing level creeps up to 1700m.

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

Likelihood

Likely

Expected Size

1 - 2

Valid until: Apr 12th, 2015 2:00PM