Avalanche Forecast

Issued: Mar 23rd, 2013 9:07AM

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

Avalanche Canada triley, Avalanche Canada

Very large cornices have been falling off naturally and triggered by people moving near them. Expect cornices to continue to fall during this period of sunny weather.

Summary

Confidence

Good

Weather Forecast

Overnight and Sunday: Some convective energy may cause localised flurries with little accumulation overnight. Convective energy should be reduced on Sunday as the High pressure system moves over the Interior. Expect mostly sunny skies with light Southwest winds and freezing levels rising to about 1300 metres. Strong solar radiation may cause moist snow up to 2100 metres on Southerly aspects.Monday: The surface ridge of High pressure should stay mostly intact as it slides a bit to the East. Expect mostly sunny skies with light Southwest winds and freezing levels rising to about 1400 metres.Tuesday: Some cloud is expected to drift into the interior from a weak disturbance on the coast. There is a chance of flurries that may accumulate a couple of cms.

Avalanche Summary

Very large cornices released naturally and with explosives in several parts of the region. Some cornice falls caused a slab approximately 120 cms deep to release in the track or the fan. Loose dry snow sluffing was reported from shaded aspects in the alpine.

Snowpack Summary

Cornices are reported to be very large and weakly bonded. Natural cornice falls are a concern during daytime warming. Cornices may also be triggered easily by travelling near them. Slopes with corniced entrances, or exposed to cornice falls should be avoided with these conditions. Dry windslabs may be found on Northwest thru Northeast aspects at higher elevations. These wind slabs are reported to be improving their bond to the old surface, but may continue to be triggered by skiers and riders. Loose moist or wet snow may fall naturally out of very steep terrain on sun exposed slopes. Small loose snow avalanches may trigger the recent storm snow slab where it is moist from solar heating and sitting on a planar sliding surface like an old sun or rain crust. The weak layer of buried surface hoar from March 10th is down more than a metre in most places, and is reported to require hard forces to result in resistant failures in snow profile tests. Some shallow snowpack areas in the region report a weak facetted base layer that continues to be a concern for human triggering.

Problems

Storm Slabs

An icon showing Storm Slabs
Recent storm slabs and wind slabs may continue to be triggered by human activity. Periods of strong solar radiation may release the storm slab where it is sitting on a buried crust.
Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Cornices

An icon showing Cornices
Large cornices may fall off naturally during periods of strong solar radiation. Cornices may also be triggered by people travelling near to them.
Do not travel on slopes that are exposed to cornices overhead.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine.

Likelihood

Likely

Expected Size

2 - 5

Persistent Slabs

An icon showing Persistent Slabs
A deeply buried weak layer of surface hoar may be triggered by large loads like cornice failures or storm slab avalanches in motion.
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Mar 24th, 2013 2:00PM