Avalanche Forecast

Issued: Feb 11th, 2013 3:00PM

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

jfloyer, Avalanche Canada

Northwest Coastal.

The focus of the snowfall is along the extreme coast. The high rating for Tuesday may be a bit aggressive in areas with less than 20 cm new snow.

Summary

Confidence

Fair - Intensity of incoming weather is uncertain on Tuesday

Weather Forecast

Synopsis: A frontal system is moving across the area bringing moderate to heavy snowfall Monday night and into Tuesday. By Wednesday, a ridge of high pressure sets up, which should hold until Thursday afternoon.Monday night: 5-10 cm new snow overnight with strong SW winds and freezing level around 700m.Tuesday: 10-20 cm new snow, with strong to extreme SW winds gusting to 80km/h at ridgetop. Freezing level around 1000m.Wednesday: Dry, with a mix of sun and cloud. Freezing level falling to valley bottom. Moderate NW winds in the morning, diminishing through the day.Thursday: Dry until the afternoon, with cloud increasing through the day. SW winds starting light, increasing to moderate through the day.

Avalanche Summary

Loose snow avalanches were reported on solar aspects from Sunday. Small avalanches (size 1) were human-triggered in wind slab deposits on Saturday.

Snowpack Summary

Recent weather has been relatively benign, with generally light snowfall adding 5-10cm at a time. Relatively light winds have accompanied these snowfall pulses with some stronger outflow winds closer to the coast. At elevations below 1300 m you might find a crust close to the surface from recent warm temperatures and/or rain.In the upper snowpack, various melt-freeze crusts remain a concern. Depending on your location, you may encounter crusts as shallow as 40cm and as deep as 110cm. Recent compression tests show both resistent and sudden planar results and an extended column test indicated a propensity for propagation if the layer was triggered. It is certainly worth keeping these layers on your radar in regards to distribution and reactivity in the areas that you are riding. The mid and lower snowpack is generally well settled..

Problems

Storm Slabs

Rapid loading from new snow and winds will lead to touchy slab avalanche conditions, especially in exposed areas.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Avoid freshly wind loaded features.>Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 4

Persistent Slabs

Various crust layers in the upper snowpack (location specific) still show sudden results and a propensity for propagation in snowpack tests. Local investigation to test distribution and reactivity is a good idea before committing to steep slopes.

Assess start zones carefully and use safe travel techniques.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 6

Valid until: Feb 12th, 2013 2:00PM