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 and Deep Persistent Slabs.

bcorrigan, Avalanche Canada

Purcells.

Warming temperatures and Solar radiation will play a leading role in the avalanche hazard in the coming days. Pay special attention to large mature cornices !

Summary

Confidence

Fair - Freezing levels are uncertain

Weather Forecast

Synopsis: A high pressure ridge will dominate the weather pattern for the next few days bringing warm temperatures and clear skies.Tonight: Clear with some cloudy periods, no precipitation, freezing level dropping to valley bottom. Ridge top winds light to moderate from the south west.Wednesday: Sunny with cloudy periods, no precipitation in the forecast, freezing level rising to 1800m. winds from the south west, light to moderate.Thursday: Cloudy periods, possibility of flurries, freezing level around 1500m. Light to moderate ridge top winds.Friday:Â Cloudy with isolated flurries, trace of precipitation, freezing level around 1600m, light, locally moderate south west ridge top winds.

Avalanche Summary

Large natural avalanches are still being reported throughout the forecast area.Â Explosives control has also produced some quite large results in some cases with wide propagations running full path over 1600 vertical metres. Cornice failures are beginning to show up on the reports, and yesterday a size 2.5Â 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. .

Snowpack Summary

The recent snowfall in now developing into a dense slab. In some deeper snowpack areas 80 to 100cm of storm slab overlies a weak surface hoar layer that has been preserved in sheltered areas. A buried sun crust exists on solar aspects and and 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 many 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 is settling 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.

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

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.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

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