Avalanche Forecast

Issued: Feb 12th, 2015 8:42AM

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

pgoddard, Avalanche Canada

Purcells.

Think twice before getting on a steep alpine face today. Large avalanches are still possible.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Temperatures are very warm (freezing level peaking near 2700 m) on Thursday and Friday, before cooling on Saturday with the passage of a cold front. Light precipitation is expected on Friday, followed by 5-10 mm precipitation on Saturday. This tapers to flurries on Sunday. Winds are light to moderate SW, changing to NW on Saturday as the front passes through.

Avalanche Summary

Natural avalanche activity has been tapering since last weekend's storm cycle, but skiers and explosives were still producing large avalanches on Wednesday: A skier triggered a size 2 persistent slab avalanche on the mid-Jan layer in the Dogtooth range and went for a ride. Explosives also triggered a size 3 slab which started with a cornice failure, then ripped out to ground. Explosives triggered a size 2.5 avalanche on the November crust/facet layer in an area that had previously slid and then reloaded. A very large natural slab was also observed just outside the region near Invermere (look for the blue pin on the bulletin regions map to get the full report). Clearly the snowpack is still capable of producing destructive avalanches, so tread carefully.

Snowpack Summary

At high elevations, 40-60cm of rapidly settling snow sits over the late-Jan crust/surface hoar layer. Rain has recently soaked the snow surface up to around 2000m and moist snow is reported to at least 2200m. Overnight cooling may be forming a weak surface crust at some elevations. Strong SW winds have left wind slabs on lee alpine features. The mid-January surface hoar is typically down 50-80cm and has been very reactive in some areas. The mid-December weak layer is down around 1m but its reactivity has been isolated recently. The mid-November weak layer of crusts and facets can still be found near the bottom of the snowpack. It has generally been unreactive but one explosive triggered avalanche occurred on it recently in a reloaded area that had slid previously.

Problems

Persistent Slabs

Large persistent slab avalanches have been releasing this week. There is still a real possibility of triggering one of these beasts with the weight of a person or snowmobile. A cornice fall or wind slab could also trigger a persistent slab.

Avoid common trigger points like convexities or areas with a thin or variable snowpack.>Use conservative route selection, stick to moderate angled terrain with low consequence.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 5

Wind Slabs

Wind slabs may be lurking on lee and cross-loaded features in the alpine. Cornices are weak with warm temperatures and may collapse.

Be cautious as you transition into wind affected terrain.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Loose Wet

Warm temperatures and drizzle have weakened the snowpack, especially at low elevations.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Be cautious of sluffing in steep terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Feb 13th, 2015 2:00PM