Avalanche forecast

Lizard-Flathead

Mar 3, 2017Avalanche Canada
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Archived · expired 10 years ago

Avalanche danger

Fri
Sat
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Alpine temperatures rising to 0 degrees, more snow and wind is driving the danger rating to HIGH.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–2
    Reactive storm slabs continue to build and are primed for rider triggering. Looming cornices exist and failures could initiate slabs on the slope below.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–4
    There have been two natural deep persistent slab releases in the past week. Both of these avalanches were on northeast aspects in the alpine, and released to size 3 or larger.

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Friday: Snow amounts 10-20 cm by Friday afternoon. Ridgetop winds light with gusts up to 80 km/hr from the SW. Alpine temperatures near 0 and freezing levels rising to 1400 m by the afternoon. Saturday: Snow amounts 10-20 cm overnight Friday and tapering off Saturday. Confidence remains low in actual  amounts and timing. Rigetop winds gusting to 75 km/hr from the SW. Alpine temperatures near -1 and freezing levels 1200 m. Sunday: Unsettled conditions with a trace. Ridgetop winds generally light from the SW and freezing levels falling to 1100 m.

Avalanche Summary

Numerous explosive results up to size 1.5 were reported from the Lizard Range on Thursday. Loose dry avalanches were also noted from steeper terrain features at treeline and below. On Friday, alpine temperatures are expected to rise to 0 degrees with more forecast snow and wind. This recipe may create an upside down feel to the snowpack (denser slab). I suspect if the weather forecast is accurate we'll see another round of natural slab avalanches. This is also driving the danger ratings to HIGH.

Snowpack Summary

A metre of low density storm snow has fallen in the past week burying a variety of old now surfaces including surface hoar, facets (sugary snow), stiff wind slabs, sun crust on solar aspects and a widespread rain crust below 1900 m. The recent storm snow is reportedly showing a poor bond to these older snow surfaces. Strong winds from the SW are likely transporting the new snow onto leeward slopes, building thicker and stiffer slabs and promoting large cornice growth. Isolated basal weaknesses may still exist in shallow snowpack areas. These weak areas appear to be on north-northeast aspects in the alpine.

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