Avalanche Forecast

Issued: Apr 9th, 2014 9:34AM

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

jfloyer, Avalanche Canada

South Rockies.

Summary

Confidence

Good

Weather Forecast

Thursday: Dry and sunny. Freezing level around 2300 m. Light NW winds. Friday: A mix of sun and cloud with the odd shower. Freezing level around 2100 m. Winds 20-30 from the west. Friday night: 5-10 mm precipitation expected as a mix of rain/snow. Light winds. Saturday: A mix of sun and cloud with occasional showers. Freezing level 1500 m. Light Winds.

Avalanche Summary

A size 3.0 avalanche in the Harvey pass area on April 4th was reported to have started from a cornice fall and stepped down to the February deep persistent weak layer.

Snowpack Summary

Very warm temperatures over the past few days and high freezing levels with no crust recovery have resulted in moist or wet snow at all elevations.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

Deep Persistent Slabs

Prolonged periods of warming, intense sunshine and/or cornice falls are the most likely triggers for deeply buried weak layers.

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

Daytime heating makes cornices droop and become unstable.

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

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Loose Wet

Warm weather and particularly strong solar radiation makes the snow surface unstable, increasing the likelihood of a loose wet avalanche.

Aspects: North, North East, East.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Apr 10th, 2014 2:00PM