Avalanche Forecast

Issued: Mar 5th, 2014 9:01AM

The alpine rating is high, 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.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

Wednesday night: 10-15cm of new snow / Strong southwest winds / Freezing level at about 900mThursday: 10-15cm of snow / Moderate southwest winds / Freezing level at about 1200mFriday: About 10cm of snow / Moderate to strong southwest winds / Freezing level at about 1500mSaturday: 20-30cm of snow / Moderate to strong southwest winds / Freezing level 1600-2000m

Avalanche Summary

A size 2 persistent slab avalanche was remotely triggered from a distance of 10m on Monday. The avalanche failed on the February 10th interface. In addition, numerous natural storm slab avalanches to size 2 were reported at all elevation bands in the region, although I suspect observations have been limited due to steady snowfall. I expect avalanche activity to increase in size and frequency with forecast weather.

Snowpack Summary

A punchy storm slab overlies small surface hoar in sheltered areas, a sun crust on solar aspects and wind slabs at higher elevations. The height of the storm snow may exceed 60cm in some areas, but in exposed terrain these new accumulations have been pushed into much deeper deposits by generally moderate southwest winds. Ongoing snowfall, wind and warming will add to the reactivity and destructive potential of this developing storm slab.There is ongoing concern a mix of weak surfaces which were buried on February 10th. This persistent interface lies between 80 and 140cm 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, large and destructive human triggered avalanches are still possible, particularly with the increased load of the new snow.For the most part, the mid and lower snowpack are strong and well consolidated.

Problems

Storm Slabs

Ongoing snowfall, wind and warming have added to the reactivity and destructive potential of a punchy storm slab which overlies a number of potentially weak layers. In many areas conservative terrain selection has become critical.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

A deep, dense slab overlies a variety of weak layers which are still producing surprise avalanches with the potential for wide propagations. The likelihood of triggering this weakness may increase with the load of the new snow.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Mar 6th, 2014 2:00PM