Avalanche Forecast

Issued: Mar 11th, 2014 9:38AM

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

jlammers, Avalanche Canada

South Columbia.

Elevated danger ratings will persist, especially with forecast warm temperatures. If solar radiation is strong the avalanche danger may exceed posted levels.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

The current dry ridge of high pressure will break down somewhat allowing for increased cloud and isolated flurries on Wednesday evening. The ridge is expected to rebuild on Thursday with mainly clear skies before an upper trough bring light snowfall on Friday. Winds should remain light with moderate gusts from the west/northwest. Freezing levels should hover around 1800m on Wednesday, 1700m on Thrusday, and about 1500m on Friday.

Avalanche Summary

On Monday explosives control produced storm and deep persistent slab avalanches to size 3.5 which occurred on all aspects at treeline and above. On the same day a splitboarder triggered a size 2.5 storm slab on a west aspect in the Revelstoke area. No injuries were reported. In the southeast corner of the region a vehicle remotely triggered a size 2.5 slab avalanche from the ridge above. The February 10th interface was responsible for this event.Last Saturday's avalanche fatality occurred in the Keefer Lake area northeast of Cherryville. The avalanche, which occurred in a cut block at about 1700m, involved 3 sledders who were in a party of 6. 2 of the men were able to inflate their airbags and were partially buried. The deceased was reportedly not able to inflate his airbag, and was buried approximately 5m below the surface.

Snowpack Summary

In some areas over 80cm of recent storm snow overlies small surface hoar in sheltered areas and a sun crust on previously sun exposed slopes. In wind exposed terrain these new accumulations have been pushed into much deeper deposits by generally moderate southwest winds. The recent storm snow may be particularly reactive in high elevation lee terrain or on sun-exposed slopes where it likely overlies the buried crust. Low elevation terrain and sun-exposed features are likely seeing a daily melt-freeze cycle. At ridgetop cornices are large, unsupported and waiting for the right trigger.The mix of weak surfaces which were buried on February 10th is still reactive. This persistent interface lies between 100 and 200cm below the surface, and includes surface hoar, well developed facets and a mix of hard surfaces which remain widespread at all aspects and elevations. This deeply buried layer continues to fail with remote triggers in isolated terrain. Likely triggers include a surface avalanche in motion, a cornice fall and solar radiation.For the most part, the mid and lower snowpack are strong and well consolidated.

Problems

Storm Slabs

Storm slabs may become less likely to trigger in some areas, but solar warming may reactivate natural activity. Storm slabs may be particularly reactive in lee alpine terrain or on sun-exposed slopes where they likely overlie a buried crust.

The new snow will require several days to settle and stabilize.>Be cautious as you transition into wind affected terrain.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 4

Deep Persistent Slabs

The early February weak layer may be less likely to trigger, but remote triggers continue in isolated terrain. Very large avalanches may result from a storm slab in motion, a cornice fall or intense solar radiation.

Avoid convexities or areas with a thin or variable snowpack.>Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Cornices

Recent storms have formed large cornices which are likely unstable. Cornices may be destructive by themselves and could also become a trigger for an avalanche on the slope below.

Extra caution needed around cornices with current conditions.>Cornices become weak with daytime heating. >Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 4

Valid until: Mar 12th, 2014 2:00PM