Avalanche Forecast

Issued: Mar 11th, 2014 9:29AM

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

Cariboos.

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 1500m on Wednesday, 1400m on Thrusday, and about 1600m on Friday.

Avalanche Summary

On Monday evidence of a natural avalanche cycle to size 3.5 was observed. The activity likely occurred on Sunday with many of the avalanches releasing on the February 10th interface. Large cornice fall was also reported in the region. A report also came in about a close call on Sunday. A ski touring party had 1 partial burial and a full burial by what sounds like a size 3.5 avalanche in the Ozalenka Valley south of McBride. The slab thickness was about 100cm and the avalanche covered about 8 hectares. Everybody walked/skied away from the incident.Looking forward, more natural activity may occur on solar aspects with forecast sunny breaks and warming.

Snowpack Summary

Up to 80cm of snow fell over the past week. This storm slab overlies small surface hoar crystals in sheltered areas and a sun crust on previously sun-exposed slopes. The storm snow may be strengthening somewhat, although it may continue to be reactive in wind exposed terrain or where it overlies the buried crust. Low elevation terrain and sun-exposed slopes are likely seeing a daily melt-freeze cycle. Cornice development has also been significant.There is ongoing concern for a mix of weak surfaces which were buried on February 10th. This persistent interface lies about a metre below the surface, and includes weak surface hoar, well developed facets and a mix of hard surfaces which remain widespread at all aspects and elevations. Potential triggers at this point include a surface slab in motion, a large cornice fall, or intense solar warming.For the most part, the mid and lower snowpack are strong and well consolidated. Weak basal facets exist in some areas, but triggering is unlikely.

Problems

Storm Slabs

Recently formed storm slabs may become less likely to trigger, but solar warming may reactivate natural activity. Storm slabs may be particularly reactive on sun-exposed slopes where they likely overlie a buried crust.

The new snow will require several days to settle and stabilize.>Be alert to conditions that change with elevation.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3

Deep Persistent Slabs

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

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - 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.

Give cornices a wide berth when travelling on or below ridges.>Cornices become weak with daytime heating. >Do not travel on slopes that are exposed to cornices overhead.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 4

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