Avalanche Forecast

Issued: Mar 29th, 2013 10:14AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Loose Wet, Cornices and Persistent Slabs.

mpeter, Avalanche Canada

Kootenay Boundary.

Danger could INCREASE TO CONSIDERABLE with intense radiation on south and west aspects, especially at treeline and below. Be aware of how the warm weather is changing the snowpack.

Summary

Confidence

Good

Weather Forecast

Saturday/Sunday: The high pressure system digs deeper! Winds remain light under clear, sunny skies. Alpine temperatures climb to 5 degrees each afternoon with freezing levels reaching 2600m.Monday: The ridge should begin to break down. Skies will remain mostly clear, light westerly winds should begin to blow and alpine temperatures will climb to just above freezing.

Avalanche Summary

On Wednesday, numerous loose wet avalanches up to size 2 were reported East through West aspects at all elevations. Be aware of overhead hazards such as cornice fall. It is likely that natural loose wet, or wet slab avalanche activity will persist through the weekend.

Snowpack Summary

Large cornices loom over many slopes. Cornice fall can act as a large trigger on slopes below, and may trigger a deeper instability if it exists. The upper 10-30cm of surface snow has become moist up to 2300 m, and melt-freeze crusts exists on solar aspects. On Northerly aspects surface hoar growth (up to 12 mm) and surface facetting is occurring.A cohesive slab overlies an old crust (down 50-60 cm) which exists up to ridge top. The crust appears to have gained some strength in most places, and some test results are showing resistant planar fracture characteristics. This layer may be harder to trigger, but should remain on your radar. It may be triggered by larger loads or skiers or riders hitting the sweet spot from a thinner snowpack area. With the weekend warm-up, wet slab avalanches may initiate naturally on this crust. Deeper down, another buried surface hoar layer sits approximately 80 cm. In some places it may not be a concern due to the thick supportive crust that lies above it. Because snowpack variability exists, it is important to dig down and test weak layers before diving into your line.

Problems

Loose Wet

Solar aspects are likely to see loose wet avalanches when the sun comes out and temperatures start to warm.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

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

Elevations: All elevations.

Likelihood

Very Likely - Certain

Expected Size

1 - 4

Cornices

With solar radiation and warm daytime temperatures, cornices may become unstable. There is a chance the weight of a cornice dropping onto the slope below could trigger an avalanche on the Mid-March crust.

Extra caution needed around cornices with current conditions.>Avoid areas with overhead hazard.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

2 - 5

Persistent Slabs

Slab avalanches have been reactive to human triggering. The weak interface being the Mid-March crust down 40-60 cm below the surface. It may be more reactive in areas that have been slightly affected by the wind.

Be aware of thin areas that may propagate to deeper instabilites.>Dig down to find and test weak layers before committing to a line.>Plan escape routes and identify safe zones before committing to your line.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely

Expected Size

2 - 6

Valid until: Mar 30th, 2013 2:00PM