Avalanche forecast

Purcells

Apr 3 – 4, 2012Avalanche Canada
View on map
Archived · expired 14 years ago

Avalanche danger

Thu
Fri
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
Open full map

Highlights

The forecast storm is expected to be short and intense. The avalanche danger is expected to reach high by the afternoon or early evening.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    3–5
    Forecast new snow and strong southwest winds are expected to develop new windslabs on the alpine and at treeline. Windslab avalanches may trigger storm slabs resulting in large avalanches.

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    3–6
    Large cornices are expected to develop new growth with forecast snow and wind. Cornice falls may trigger slopes below resulting in very large avalanches.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    2–6
    Forecast new snow is expected to add a new load to the storm slabs that are already a metre deep in some parts of the region. This new load may cause natural avalanches or easily triggered avalanches.

Confidence

Fair - Forecast snowfall amounts are uncertain on Wednesday

Weather Forecast

A low pressure system is forecast to move into the region on Wednesday morning from the south bringing heavy precipitation combined with strong southeast winds. Strong southwest winds are expected to diminish to moderate southeast at the beginning of the storm, and then become light easterly by Wednesday evening. Moderate precipitation is expected to continue overnight and into Thursday. About 20 mm of precipitation are expected on Wednesday, and another 10-15 mm is expected overnight and Thursday. The high freezing level from Tuesday should begin to drop overnight and hover about 1200 metres on Wednesday, and stay there for most of Thursday.

Avalanche Summary

There were some explosive controlled avalanches up to size 3.0 that released in the storm snow down about 70 cm on various aspects. Avalanches releasing on the deeply buried mid-February surface hoar are becoming less likely. Avalanches may step down to the weak layer of facets or depth hoar on a crust that was buried in October.

Snowpack Summary

The recent storms have added up to about a metre of snow in the region. High freezing levels have consolidated the storm snow into a cohesive slab that may be propagated remotely. The storm snow slab is sitting on top of a sun crust that was buried on March 27th on southerly aspects, and above wind affected surfaces that may be facetted on northerly aspects. Forecast new snow will add another load that may cause another cycle of natural avalanches or easily triggered avalanches. Cornices are reported to be very large in the region, and new cornice growth is expected with forecast new snow and strong southerly winds. The mid snowpack is well settled and strong. There is a weak layer of facets or depth hoar in shallower snowpack areas that may fail with initial warming of the snowpack. There is also a weak layer of of facets or depth hoar above a crust at higher elevations where there was already snow in October.

Regions covered