Avalanche Forecast

Issued: Apr 7th, 2014 9:40AM

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

jfloyer, Avalanche Canada

South Rockies.

These blog posts about warming and cornice hazard are very relevant right now.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Tuesday

Weather Forecast

Warm weather is expected to persist through Tuesday before a pulse of precipitation associated with the passage of a cold front is expected Tuesday night, followed by a drop in temperature. Tuesday: Warm. Sunshine expected in the morning, becoming cloudy in the afternoon. Freezing level as high as 2800 m. Winds starting light, becoming moderate SW. Tuesday night: 2-5 mm of rain/sleet/snow with strong SW winds. Wednesday: Lingering flurries in the morning, becoming dry and bright later. Freezing level around 1800 m. Light NW winds. Thursday: Dry. Cloudy with some sunny breaks. Freezing level around 2200 m. Light westerly winds.

Avalanche Summary

Loose moist avalanches up to size 1.5 were reported that entrained surface snow in the track, but did not step down to deeper weak layers. Little or no overnight freeze on Monday night with additional warming on Tuesday may result in large avalanches stepping down to deep layers.

Snowpack Summary

In the Smith Basin area there is 140 cm below treeline and the top 40 cm was found to be moist and well consolidated. The March crust below was decomposing at this location. The February deep persistent weak layer was down 80 cm and well preserved. Higher up at about 2300 metres the height of snow was a little over two metres. The March crust was not intact at this location and did not result in any shears in snow profile tests. The February deep persistent weak layer (DPWL) was down 100 cm and was a well defined layer of softer facetted snow below the hard (pencil) snow of the well settled mid-pack. Hard sudden collapse shears were recorded at the interface of the February DPWL. In the Elk Valley South the height of snow at 1900 metres was 430 cm. The snow was dry and loose above 1700-1800 metres and moist below where loose wet slides had released on solar aspects. There was a 2-3 cm supportive crust on Southerly aspects above 1900 metres, and no crust on shaded North aspects.

Problems

Wet Slabs

At higher elevations, recent storm snow could easily shed during periods of intense sunshine when no refreeze occurs overnight. At lower elevations, glide cracks have been reported and should be avoided.

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: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Deep Persistent Slabs

Avalanches releasing on the deeply buried weak layer from early February are still a concern. Strong solar radiation, cornice falls, new loading, or storm slab avalanches in motion are all possible triggers.

Caution around convexities or areas with a thin or variable snowpack.>Consider the consequences of the terrain if an avalanche steps down to a persistent weakness.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Cornices

Cornices are a danger in themselves, but also have the potential to trigger a slab avalanche on the slope below. See this blog post for a story about a recent near miss.

Give cornices a wide berth when travelling on or below ridges.>Do not travel on slopes that are exposed to cornices overhead.>

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

Elevations: Alpine.

Likelihood

Likely

Expected Size

1 - 5

Valid until: Apr 8th, 2014 2:00PM