Avalanche Forecast

Issued: Apr 3rd, 2012 10:43AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Wind Slabs, Cornices and Loose Wet.

mbender, Avalanche Canada

Kootenay Boundary.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain on Wednesday

Weather Forecast

WEDNESDAY: Light to locally moderate amounts of precipitation. Moderate northerly winds with a freezing level of 1000-1200m. THURSDAY & FRIDAY: Broken skies with light flurries and light winds. Freezing levels remain steady at 1000-1200m.

Avalanche Summary

The region has been very active with avalanches the past 4 days. Natural, explosive and human triggered avalanches have been reported up to size 2.5. Reports come from all aspects, with a bias to north facing slopes. At lower elevations (where the surface is moist) these are running as loose events and at higher elevations the new snow is propagating as a slab. Remote triggering has also been observed.

Snowpack Summary

Up to 100cm of new snow has fallen since March 26. Shears within the upper storm snow are tightening with the persistent warm temperatures, although a reactive layer down 40-50cm remains. The March 26 interface is a melt freeze a crust on all aspects except true north treeline and alpine, where small surface hoar (5mm) is present in sheltered places. The bond at this interface is gaining strength, with lingering concerns on true south aspects where the crust is thickest and where the surface hoar lurks. At lower elevations, the consistent high freezing levels have kept the new snow heavy and moist. The deep, persistent early February surface hoar lingers in the snowpack giving sudden results in testing. Concern remains with heavy triggers (cornice), step down avalanches and rapid loading from intense precipitation, strong winds or sun.

Problems

Wind Slabs

The increased wind and new snow have formed windslabs in lee zones at ridgecrest. A small windslab event could step down to the deep, persistent weakness.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 6

Cornices

Cornices continue to grow. There is potential for triggering deep persistent slabs on underlying slopes.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 7

Loose Wet

Short periods of sun can be enough to cause avalanches to run on sun exposed slopes.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Apr 4th, 2012 9:00AM