Avalanche Forecast

Issued: Mar 14th, 2014 9:56AM

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

rbuhler, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

The next storm system is expected to reach the north coast on Saturday morning. Heavy precipitation and strong winds are expected for Saturday and Sunday. Conditions should be milder to the north of the region. A ridge of high pressure should build on Monday.Saturday: Precipitation 15-20mm, freezing levels am: 600m pm: 1200m, ridgetop wind 40-60 km/h S-SWSat. Night/Sunday: Precipitation 15-25mm, freezing levels am: 1200m pm: 500m, ridgetop wind 40-60 km/h S-SW in the morning, easing during the dayMonday: Light flurries, freezing levels am: 300m pm: 600m, ridgetop wind light SW

Avalanche Summary

Widespread natural avalanche activity up to size 4 was reported on Tuesday and Wednesday. Many very large events were reported with avalanches running full path. Natural activity has tapered off on Thursday but we received reports of explosive and human-triggered avalanches up to size 3. A remotely triggered size 3 avalanche occurred on the early Feb persistent weak layer. This was triggered from 150m away and was 50-200cm deep.

Snowpack Summary

Storm slabs continue to build. At the end of the last storm pulse, the storm slab was up to 1m thick in the north of the region. The south of the region had less snowfall and the slab is roughly 60cm thick. These slabs generally sit on a weak layer which may consist of any of the following: hard wind slabs or wind-scoured slopes in exposed terrain, a thick layer of faceted snow on sheltered, shady slopes, isolated surface hoar on sheltered, shady slopes, and sun crust on steep solar aspects. Snow below 1000-1200m has been wet and been through several melt-freeze cycles. The mid February weak layer of surface hoar or a crust/facet combo is typically buried over 1.5m deep. This layer continues to react in snowpack tests, primarily on sheltered north aspects at or below treeline. The weight of the new snow and rain has the potential to reactivate this layer resulting in large, destructive avalanches. Basal facets and/or depth hoar remain an isolated concern in shallow snowpack areas in the northern part of the region.

Problems

Storm Slabs

Heavy snowfall and strong winds will continue to build storm slabs on Saturday. Strong forecast SW winds should quickly form new wind slabs on leeward aspects.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

3 - 6

Deep Persistent Slabs

The weak layer from early Feb is down roughly 1.5m and continues to be reactive in isolated areas. Heavy triggers such as storm avalanches or cornice falls have the potential to trigger this deep layer which would resulting in very large avalanches.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Be aware of thin areas that may propogate to deeper instabilites.>Avoid lingering in runout zones.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 7

Valid until: Mar 15th, 2014 2:00PM