Avalanche forecast

Purcells

Feb 8 – 9, 2015Avalanche Canada
View on map
Archived · expired 12 years ago

Avalanche danger

Tue
Wed
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
Open full map

Highlights

Storm problems will persist on Monday, especially at higher elevations. Conservative decision making remains critical and travel in avalanche terrain is not recommended.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    2–5
    Buried persistent weak layers in the mid-pack have become reactive with heavy storm loading resulting in large avalanches. A dormant deep persistent weakness near the ground also has the potential to wake-up with the additional load.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    2–5
    Strong winds, heavy snowfall, and high freezing levels have created widespread storm slabs at higher elevations. Continued storm conditions will add to these highly reactive slabs.

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–5
    Continued rain at lower elevations may result in wet slab avalanches running to valley bottoms. Loose wet avalanches are expected from steep terrain features.

Confidence

Fair - Freezing levels are uncertain on Tuesday

Weather Forecast

The last major frontal system will reach the interior Sunday overnight. On Monday, the region is expected to see 5-15mm of precipitation. Freezing levels should drop to below 1000m Sunday overnight but should rise back to around 1800m on Monday. Alpine winds are expected to be moderate-to-strong from the SW. On Tuesday, things should dry out as a ridge of high pressure builds but mostly cloudy conditions are expected and lingering flurries are possible. Freezing levels should remain around 1500m and alpine winds should be light. A mix of sun and cloud is expected for Wednesday with unseasonably high freezing levels persisting. However, during the overnight periods, temperatures should drop and we should see spring-like diurnal temperature cycles.

Avalanche Summary

Widespread natural, human-triggered, and explosive controlled avalanches up to size 3 were reported on Friday and Saturday. This includes both storm slabs and persistent slabs.  Many avalanches started dry and ended wet, running to valley bottom.  On Sunday, a skier was involved in an accident in the Canyon Creek area.  The subject was caught in a size 2.5 persistent slab which resulted in serious injuries. The avalanche released on the mid-January surface hoar layer down around 80cm. On Monday, natural avalanches remain likely at upper elevations where storm and wind loading continue. At lower elevations which have seen rain, natural activity is less likely but remains possible. Human-triggering remains very likely at higher elevations on Monday.

Snowpack Summary

40-60cm of recent storm snow has fallen over the late-Jan weak layer at higher elevations. Rising freezing levels during the storm have created upside-down snow conditions and highly reactive storm slabs. Rain has soaked the snow surface up to around 2000m and moist snow is reported to at least 2200m. Strong SW winds have formed wind slabs in exposed leeward terrain features. The storm slab sits on an old rain crust at lower elevations, variable surface hoar, and/or wind affected surfaces at higher elevations. Multiple weaknesses within the storm snow are also expected.  The mid-January surface hoar is typically down 50-80cm and the mid-December weak layer is down around 1m. Both of these persistent layers have been reactive recently. The mid-November weak layer of crusts and facets can still be found near the bottom of the snowpack. It has been unreactive lately, but should remain on your radar, especially in shallow snowpack areas.

Regions covered