Avalanche Forecast

Issued: Mar 12th, 2014 9:53AM

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

bcorrigan, Avalanche Canada

Purcells.

The hazard may go higher than forecast below tree line with daytime heating, especially on solar aspects. Be aware of large, mature cornices. For more insight into what's going on, check out the latest:Forecasters Blog.

Summary

Confidence

Fair - Freezing levels are uncertain

Weather Forecast

Synopsis: The ridge of high pressure holds for the next few days with clear skies and warm spring-like conditions. There is a possibility of moisture by the weekend.Tonight: Clear periods, freezing level around 1000 metres. ridge top winds light, occasionally gusting to strong from the west.Thursday: Sunny with cloudy periods, freezing level around 1300m. Light ridge top winds occasionally gusting to moderate.Friday:Â Cloudy with sunny periods, light precipitation in the north, up to 15cm in the south, freezing level around 1600 metres, winds from the southwest , light to moderate, occasionally gusting to strong.Saturday:Â Cloudy with scattered flurries. freezing level around 1400 metres, ridge top winds light, occasionally gusting to strong

Avalanche Summary

Large natural avalanches are still being reported throughout the forecast area. Explosives control has also produced some quite large results in some cases with wide propagations running full path over 1600 vertical metres.Â RecentlyÂ size 2.5 avalanche was triggered by snowboarders at 2600 metres on a south east aspect. Neighboring forecast regions have reported large avalanches initiating in the new storm snow, then stepping down to deeper layers, some running full path to the ground. Cornice failures triggering large avalanches have been reported.

Snowpack Summary

The recent snowfall has now developed into a dense slab. In some deeper snowpack areas 80 to 100cm of storm slab overlies a weak surface hoarÂ and facet layer that has been preserved in sheltered areas. A buried sun crust exists on solar aspects and and touchy wind slabs have formed at tree line and above. On lee slopes these accumulations have been pushed into much deeper deposits by moderate to strong southwest winds. Warming has added cohesion to the slab and wider propagations are now being reported. With rising temps and solar radiation, moist snow surfaces have been reported into the alpine. Wet avalanches on solar aspects have also been reported. There is ongoing concern for a mix of weak surfaces which were buried on February 10th. This persistent interface lies between 60 and 160cm below the surface, and includes surface hoar, well developed facets and a mix of hard surfaces which remain widespread at all aspects and elevations. In parts of the forecast area, large destructive avalanches are still a very real concern with ongoing reports of natural avalanches running full path. Weak basal facets exist in many areas, but without a large load, triggering now is unlikely.

Problems

Storm Slabs

Recent storm snow has settled into a dense slab that overlies a variety of weak layers. Warm temperatures will set the stage for natural and rider triggered avalanches, use caution in recently wind loaded terrain. Cornice hazard is a real concern.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Choose conservative lines and watch for clues of instability.>Be cautious as you transition into wind affected terrain.>Be alert to conditions that change with elevation.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Deep Persistent Slabs

Additional loading and rising temperatures make the possibility of triggering deep layers more likely. A cornice failure could produce a large enough load to trigger deeply buried weak layers.

Choose conservative lines and watch for clues of instability.>Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.>Avoid areas with overhead hazard.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

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