Avalanche Forecast

Issued: Feb 5th, 2015 8:45AM

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

ghelgeson, Avalanche Canada

Northwest Coastal.

Extreme wind and heavy snowfall should ramp up Thursday evening. Only the most conservative non-avalanche terrain is appropriate this weekend.

Summary

Confidence

Fair

Weather Forecast

Extreme southerly winds in the alpine along with strong east through south winds below treeline are expected through the forecast period. The freezing level should stay right around 600m and a few significant shots of precipitation are expected. 10 to 40 cm are possible Thursday night, another 10 to 40cm are expected Friday with 5 to 25cm on tap for Friday night. Fore a more detailed look at this dynamic weather pattern visit avalanche.ca/weather

Avalanche Summary

On Wednesday, (before the storm) a size 2.5 wind slab avalanche was reported from a steep SE facing feature at 1300m. I suspect there will be more activity to report on in the next few days.

Snowpack Summary

35- 60cm of new snow has fallen in the last few days. Strong winds have redistributed this snow in exposed terrain forming winds slabs in leeward features and stripping exposed slopes. The late-January crust is typically down 100-140cm in the south of the region and about half this depth in the north. Tests are indicating that this interface is generally well bonded but isolated avalanches have been reported to have released on this layer recently. The mid-January rain crust and/or surface hoar layer is down over 150cm in the south and has generally become inactive. It may still be a concern in thinner snowpack areas. The November crust/facet combo near the bottom of the snowpack is thought to be generally well bonded. However, this deep and destructive layer is still reported to be reactive in the far north of the region.

Problems

Storm Slabs

Significant snowfall and extreme winds are expected to drive a large natural avalanche cycle that will likely last through Saturday. Probably best to stay out of avalanche terrain while the storm is raging.

Storm slab avalanches in motion have the potential to step down resulting in large avalanches.>Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Persistent Slabs

This storm system should be a good test for the more deeply buried weak layers. With up to a meter of new snow expected in the alpine by Saturday afternoon, I wouldn't be surprised to see storm slabs step down to one of the persistent weaknesses.

Be aware of thin areas that may propogate to deeper instabilites.>Be aware of the potential for large, deep avalanches due to the presence of buried crusts and/or surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Feb 6th, 2015 2:00PM