Avalanche forecast

Purcells

Mar 11 – 12, 2013Avalanche Canada
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Archived · expired 14 years ago

Avalanche danger

Wed
Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Forecasted amounts of precipitation spatially vary in the region. This forecast reflects areas that will receive the most amounts; possibly the East and South part of the region.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–6
    Persistent weak layers exist buried down 60-90 cm, comprising of surface hoar and a sun crust. It could be triggered by the forecasted precipitation and warm temperatures.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–4
    Precipitation and warm temps are expected in the days to come creating new storm slabs at all elevations and new wind slabs lee of strong SW winds in the alpine and treeline. The potential avalanche size is expected to increase as more snow piles up.

Confidence

Fair - Forecast snowfall amounts are uncertain for the entire period

Weather Forecast

Monday Night and Tuesday: The first of a series of systems approaching the interior is expected to start spreading precipitation over the region early Tuesday. Light to moderate precipitation amounts (more on the Eastern part of the region) are expected with strong SW winds . Freezing level will start rising to reach around 1600 m. and will stay high for the rest of the period.Wednesday: Precipitation easing off but still some moisture available. Winds are forecasted to be strong to extreme from the SW. Temperatures staying warm and freezing levels up to 1900 m. in the S part of the region. Thursday: Another burst of precipitation is expected with similar freezing levels and lighter winds switching from the SW.

Avalanche Summary

A couple natural slab avalanche size 2.5 were reported on W and SW slopes one of which was triggered by a loose avalanche. 

Snowpack Summary

Up to 5 cm of new snow is covering a variety of surfaces; a 2 cm thick suncrust on SE-S-SW facing slopes at all elevation, a melt-freeze crust all the way up to 1600 m. and some well developed surface hoar on shaded slopes above that elevation. The forecasted precipitation and warm temperatures will add a significant load to the snowpack (possibly from 20 to 50 mm in water equivalent until Thursday). I suspect that the variety of surfaces described previously will become gradually more reactive as the load add up starting tomorrow. This could also awake the 60-90 cm deep persistent surface hoar layer that has been less reactive to skier traffic lately creating a potential for very large avalanches.

Regions covered