Avalanche Forecast

Issued: Mar 12th, 2014 9:50AM

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.

ghelgeson, Avalanche Canada

South Columbia.

The current snowpack presents a serious challenge. Check out our latest blog for a look into the recent avalanche cycle and our best guess into what the future holds.

Summary

Confidence

Poor - Freezing levels are uncertain

Weather Forecast

Synopsis: A ridge of high pressure dominates the pattern for most of Thursday giving way to a pacific front Friday. Freezing levels are forecast to remain at spring like heights for the period (1300m - 2000m). Look for clearing skies Saturday. There is very little consistency from one model to the next at this time, thus my confidence in this forecast is quite poor.Thursday: Freezing Level: 1300m - 2000m; Precip: nil; Wind: Light, SW | Mod W at ridgetop.Friday: Freezing Level: 1200m - 2000m; Precip: 4/15mm - 4/20cm; Wind: Light, SW | Mod SW at ridgetop.Saturday: Freezing Level: 800m - 1900m; Precip: 0/4mm - Trace/5cm; Wind: Mod, W | Strong SW at ridgetop.

Avalanche Summary

On Monday explosive 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.The action continued into Tuesday with skier and explosive triggered avalanches to size 3. Natural avalanches to size 2 were also observed.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

50 - 120 cm 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 80 and 250cm 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.

Dig down to find and test weak layers before committing to a line.>Be cautious as you transition into wind affected terrain.>Watch for terrain traps where small amounts of snow will acumulate into deep deposits.>Avoid areas with overhead hazard.>

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.

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

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. >Extra caution needed around cornices with current conditions.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 4

Valid until: Mar 13th, 2014 2:00PM