Avalanche forecast

Purcells

Mar 1 – 2, 2013Avalanche Canada
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Archived · expired 14 years ago

Avalanche danger

Sun
Mon
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    2–6
    Loading from new snow and wind may add reactivity to persistent buried surface hoar layers. In deeper snowfall areas, resulting avalanches may be large.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–5
    Recent new snow and wind have created new slabs, which may be particularly touchy on slopes in the lee of the wind.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    Accumulated precipitation and rising freezing levels may initiate loose wet avalanches from steeper terrain features  below treeline. Initial indicators include snowballing and moist snow surfaces.

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

As an upper trough moves towards the California coast cutting off the moisture supply of the pineapple express. This will reduce accumulations and winds over the region. Saturday: Light precipitation amounts accompanied by light-moderate ridgetop winds from the SW. Alpine temperatures near -2 and freezing levels rising to 1900 m in the afternoon with a moderate to high diurnal trends. Sunday: Light precipitation accompanied by moderate ridgetop winds from the NW. Alpine temperatures near -8 and freeing levels falling to 1000 m. Monday: No significant precipitation expected. Ridgetop winds will blow light from the South. Alpine temperatures -9 and freezing levels near 1300 m in the afternoon.

Avalanche Summary

A few skier triggered slab avalanches were  remotely triggered on Friday up to size 1.5, running far and fast. On Thursday, slab avalanches to size 1.5 were ski cut and failed naturally. Recent explosives testing in the southern portion of the region producing slab avalanches to size 2.5 isolated to the storm snow.

Snowpack Summary

Moderate amounts of new snow has fallen adding to an ongoing storm snow instability, particularly on the west side of the region where accumulations have been highest. The variably reactive February 12th and 15th surface hoar layers now exist up to 80cm below the surface and seem most prevalent on the west side of the region. This interface may also be reactive on solar aspects where a sun crust exists. A surface hoar layer buried on February 23 is still on the radar of some operators. This layer has been less likely to trigger by skiers, but may still be sensitive to large loads like avalanches in motion or cornice fall. The mid and lower snowpack are generally well settled and strong.

Regions covered