Avalanche forecast

Northwest Coastal

Feb 2 – 3, 2013Avalanche Canada
View on map
Archived · expired 14 years ago

Avalanche danger

Mon
Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
Open full map

Highlights

The "Danger Ratings" are based on 20 cm or more snow for Sunday accompanied by strong winds. If you receive less snow, consider the rating to be one step to high.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–5
    Strong SW winds will build fresh wind slabs on lee slopes and behind terrain breaks such as ridgelines and ribs. These may be reactive under the weight of a person and/or a machine. Hollow sounds, and cracking from beneath may indicate unstable snow.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–6
    Up to 80 cm sits above a persistent weakness comprising of a crust/facet/surface hoar interface. This interface may be found most reactive in sheltered areas over convex rolls or steep terrain. Dig down and see how reactive it is in your riding area.

Confidence

Fair - Forecast snowfall amounts are uncertain on Sunday

Weather Forecast

Sunday: A Pacific frontal system moves in bringing moderate to heavy precipitation amounts (25-40 mm). Ridgetop winds blowing strong from the SW. Alpine temperatures near -4.0 and freezing levels falling to 700 m. Monday: A trailing warm front moves onto the region bringing continued moisture and wind. Ridgetop winds will be strong from the South.  Alpine temperatures -5.0 and freezing levels falling to 500 m. Tuesday: Unsettled conditions prevail with cloudy skies and no significant precipitation. Areas in the north may see some sunny periods. Ridgetop winds will be light from the South. Alpine temperatures near -7 and freezing levels will fall to 200 m.

Avalanche Summary

On Friday, several natural loose, slab and glide avalanches were spotted from a heli flight up to size 2.5. I suspect loose wet avalanches continued in below treeline elevations.

Snowpack Summary

New storm snow will blanket wind slabs (NE-W) that built over the past week. With strong winds from the SW, fresh wind slabs will form on lee slopes and behind terrain features like ribs and ridgelines. Lingering beneath (down 50-80 cm) sits a persistent weakness comprising of surface hoar, facets, and /or a crust. Recent test done on these layers are producing hard results with sudden and resistant planar characteristics. The mid pack is generally well settled and strong, although basal facets remain a concern in the northern part of the region.

Regions covered