Avalanche Forecast

Issued: Feb 12th, 2014 8:18AM

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

Avalanche Canada slemieux, Avalanche Canada

If new snowfall amounts are greater than 10 cm, consider the danger rating to be higher than posted at treeline and below treeline.

Summary

Confidence

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

Weather Forecast

Tonight and Thursday: A weaker system will move across the province late tonight giving another round of precipitation over the region. Expect around 10 cm accumulation. Freezing levels should rise to 1500 m briefly and winds should blow strong to extreme from the south and then switching from the west. Friday: Moderate precipitation is forecasted with the passage of another system with similar winds and freezing levels.Saturday: After a bit of a break between systems, the steady stream of low pressure  systems will keep coming in. Expect another pulse of precipitation later during the day with similar strong winds and freezing levels.

Avalanche Summary

Several slab avalanches size 2-2.5 were triggered by explosives today in the southern part of the region. Numerous skier triggered slab avalanches size 1 were reported yesterday in the recent snow. Some of these slabs ran on the late January crust on east and south aspects or on the surface hoar interface on north and northwest aspects. There was also some sluffing out of steep terrain. Expect more and bigger avalanches with the incoming weather.

Snowpack Summary

10 cm of new snow is expected tomorrow adding to the ~25 cm already fallen. Extreme winds will most likely overload lee slopes likely producing large natural avalanches on east and northeast aspects in the alpine and at treeline. Rising temperatures during the day could also weaken the storm snow on all aspects, at all elevations.The storm snow is sitting on a variety of weak layers that formed during the recent cold snap; surface facets, a new surface hoar layer on shady aspects, a crust on solar aspects or hard windslabs in the alpine. 30-50 cm below the surface, exists a surface hoar or suncrust layer has been reactive to skier traffic even since it has been buried in late January. Anticipate that there is a good chance that avalanches will step down to this deeper buried weak layer, resulting in bigger than expected storm avalanches.The mid snowpack is strong and supportive. Deeper persistent layers have been dormant, however, they could wake up in the near future with the increasing load.

Problems

Storm Slabs

An icon showing Storm Slabs
Loading from the weight of new snow, windloading from extreme winds and rising temperatures could possibly trigger natural slab avalanches tomorrow especially on northeast and east aspects. Loose snow avalanches are also a concern.
Avoid avalanche terrain during periods of heavy loading from new snow and wind.>Minimize overhead exposure; avalanches triggered by windloading may reach run out zones.>Be aware of the potential for larger than usual storm avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

2 - 5

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