Avalanche Forecast

Issued: Mar 8th, 2014 8:17AM

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

Avalanche Canada bcorrigan, Avalanche Canada

Summary

Confidence

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

Weather Forecast

Synopsis:  An intense frontal system with subtropical moisture is just now arriving on the BC coast. Warm air preceding the Pacific frontal system has already arrived pushing freezing levels up to 2000 metres in some parts of the forecast area.Tonight: Cloudy with flurries and trace to 10cm of precipitation. Strong SW winds and freezing levels climbing to 1700m.Sunday: Cloudy, snow flurries, possibility of 5 to 10 cm of snow, winds gusting to strong at ridge tops, freezing levels may climb to 2000m.Monday: Mix of sun and clouds, trace of precipitation in the forecast, light to moderate winds at ridge tops, freezing level drops to around 1500m. Tuesday:  Sunny with cloudy periods, no precipitation in the forecast, light winds at ridge top, freezing level down to around 1400m.

Avalanche Summary

Storm slab avalanches continue to be reported running naturally. Most of the storm snow avalanches are size 1.5-2.0, however one was reported to be size 3.0 where the storm slab is now 80 cm thick. Explosives control released some large avalanches down to the early February persistent weak layer. There were also a couple of accidentally triggered storm slab avalanches, one that buried a sledder on a northwest aspect in the alpine. Expect natural avalanche activity to continue over the weekend with the continued forecast of new snow and wind.

Snowpack Summary

Recent snowfall amounts have been highly variable throughout the region. In some deeper snowpack areas over 80cm of storm snow overlies a weak surface hoar layer that has been preserved in sheltered areas. A sun crust exists on solar aspects and and there are wind slabs in exposed terrain. On lee slopes these accumulations have been pushed into much deeper deposits by generally moderate southwest winds. Warming has added cohesion to the slab and wider propagations can be expected. At lower elevations rain has likely moistened snow surfaces. 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 some areas destructive avalanches are still a very real concern with ongoing reports of natural triggering, whumpfing and sudden/easy snowpack test results. The mid and lower snowpack are generally strong and well consolidated. Weak basal facets exist in many areas, but triggering has now become unlikely.

Problems

Storm Slabs

An icon showing Storm Slabs
The storm slab is settling and becoming more dense with increasing load and warming temperatures.  Strong south west winds will redistribute the new snow into wind slabs at tree line and above on north and northeast aspects.
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

Persistent Slabs

An icon showing Persistent Slabs
The Feb. 9th persistent weak layer  has been re-awakened in some parts of the forecast area by the new load of storm snow. An avalanche that steps down to this layer will produce a large and destructive avalanche event.
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.>Avoid areas with overhead hazard.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Mar 9th, 2014 3:00PM