Avalanche Forecast

Issued: Mar 6th, 2014 9:08AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Storm Slabs and Persistent Slabs.

jlammers, Avalanche Canada

South Columbia.

This weekend's weather forecast includes higher freezing levels and rain to mid-mountain elevations. This will have a destabilizing effect on the snowpack with avalanches increasing in size and frequency.

Summary

Confidence

Fair - Freezing levels are uncertain on Friday

Weather Forecast

Thursday Night: Up to 10cm of snow / Moderate westerly winds / Freezing level at surfaceFriday: Light snowfall / Moderate to strong southwest winds / Freezing level at 1000m climbing to about 1800m in the eveningSaturday: 10-15cm of snow at higher elevations / Moderate to strong southwest winds / Freezing level at about 2000mSunday: Up to 30cm of snow at higher elevations / Moderate to strong southwest winds / Freezing level up to about 2000m

Avalanche Summary

Several natural storm slab avalanches to size 2.5 were reported on a variety of aspects and elevations on Wednesday. Numerous size 3 storm slab avalanches were also reported on south facing alpine terrain. These avalanches formed in response to new snow and wind. I would expect more of this with the potential to step down to deeply buried persistent weaknesses with forecast precipitation and rising freezing levels over the weekend.

Snowpack Summary

Up to 80cm of recent storm snow overlies small surface hoar in sheltered areas, a sun crust on solar aspects and wind slabs at higher elevations. In wind exposed terrain these new accumulations have been pushed into much deeper deposits by generally moderate southwest winds. Forecast snowfall, wind and warming will add to the reactivity and destructive potential of this developing storm slab.There is ongoing concern for a mix of weak surfaces which were buried on February 10th. This persistent interface lies between 80 and 180cm below the surface, and includes surface hoar, well developed facets and a mix of hard surfaces which remain widespread at all aspects and elevations. Although natural avalanche activity has tapered-off at this interface, it remains sensitive to remote triggers in isolated terrain and may see a significant "wake-up", particularly with the increased load of the new snow and forecast rain.For the most part, the mid and lower snowpack are strong and well consolidated.

Problems

Storm Slabs

A punchy storm slab overlies a number of potentially weak layers. Expect increased reactivity in wind-exposed terrain. Warming and light rain may also have a significant destabilizing effect at elevations below the snow line.

Good day to make conservative terrain choices.>Be cautious as you transition into wind affected terrain.>Be alert to conditions that change with elevation.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

A mix of weak, persistent layers buried about a month ago have not gone away. This weekend's forecast warming and rain may kick start this weakness with potential for very large and destructive avalanches.

Avoid convexities or areas with a thin or variable snowpack.>Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Mar 7th, 2014 2:00PM