Avalanche forecast

Northwest Coastal

Feb 11 – 12, 2013Avalanche Canada
View on map
Archived · expired 14 years ago

Avalanche danger

Wed
Thu
Alpine
4 · High
Treeline
3 · Considerable
Below
2 · Moderate
Open full map

Highlights

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.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–6
    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.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–4
    Rapid loading from new snow and winds will lead to touchy slab avalanche conditions, especially in exposed areas.

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..

Regions covered