Avalanche Forecast

Issued: Apr 22nd, 2014 9:08AM

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

esharp, Avalanche Canada

Purcells.

This forecast was build on limited field reports. If you head out into the mountains please tell us about the conditions you found. Send your observations to forecaster@avalanche.ca

Summary

Confidence

Poor - Due to the number of field observations

Weather Forecast

Synopsis: Southerly flow will continue to generate precipitation over the southern interior, Thursday will see drier conditions before an approaching trough off the coast forces a southerly flow pattern again on Friday. Tonight and Wednesday: Light precipitation continuing through the night, tapering off Wednesday afternoon - trace to 10 cm cm of snow at upper elevations. / Moderate westerly winds / Freezing levels falling to 1500mThursday: Sunny with cloudy periods and chances of flurries / Light southerly winds / Freezing levels 2000mFriday: Flurries / light southeasterly winds / Freezing levels 2000m

Avalanche Summary

Small slabs have been recently triggered naturally and by skiers in areas where the upper snow is moist and sits above a crust. At lower elevations and on solar aspects small to large loose wet avalanche continue to be triggered on steep slopes. Cornices collapses have been reported during periods of daytime warming. Occasionally these heavy triggers have caused large deep slab avalanches on the slopes below.

Snowpack Summary

Snow line reached up to 2000m yesterday.A fresh crust on all but high elevation North aspects may now be buried up to 5 cm of new snow. Below this 10 to 30cm of snow overlies older melt-freeze crusts from earlier in the month. Wind slabs can be found in lee features on N and E aspects in the Alpine.Several persistent weak layers still exist in the highly variable snowpack of the Purcells:-The mid-March sun crust/surface hoar layer down 50-80cm and the early-March crust/facet/surface hoar layer down around 80-120cm seem to be laying dormant for the time being.-The mid-February crust/facet/surface hoar combo is typically down 60 - 120cm. Direct triggering of this layer has become unlikely, however, cornice fall, a smaller avalanche in motion or prolonged warming may wake this layer up. The resulting avalanche would be very large and destructive.- Weak basal facets can be found in many areas, however triggering this layer is unlikely.

Problems

Wind Slabs

Moderate winds have redistributed recent snow and wind slabs may be found in lee features on North aspects. Below 2200m these slabs may be sitting on a recent melt freeze crust

Be cautious as you transition into wind affected terrain.>The new snow will require several days to settle and stabilize.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Deep Persistent Slabs

The potential for very large deep slab avalanches needs to remain on your radar. Cornice fall, warming temperatures or a smaller wet or wind slab avalanche in motion could act as triggers.

Be aware of the potential for very large, deep and destructive avalanches due to the presence of deeply buried persistent weak layers.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

3 - 6

Valid until: Apr 23rd, 2014 2:00PM