Avalanche Forecast

Issued: Feb 23rd, 2013 9:57AM

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

Weather Forecast

Sunday: Heavy snowfall developing late in the day and continuing overnight / Strong west winds / Freezing level at 900mMonday: Light snowfall / Light northwest winds / Freezing level at 800mTuesday: Mix of sun and cloud / Light southwest winds / Freezing level at 800m

Avalanche Summary

A size 2 slab avalanche occurred on Friday in the north of the region and resulted in a fatality. The avalanche occurred on a northeast aspect at treeline, More details will follow as they are released by the RCMP.

Snowpack Summary

Up to 50cm of new snow and wind have created potent new storm slabs which are likely to be most reactive in wind-exposed terrain. These heavy accumulations add to the 25 to 55cm of snow which overlie the weak surface hoar layer which was buried on February 12th. The additional weight of the new snow and wind affect is expected to add reactivity to this persistent weakness which remains a primary concern for professionals in the region. This interface has also shown reactivity on southerly aspects where a sun crust formed during the period from February 8th-11th. There are older weak layers (surface hoar, crusts on solar aspects, facets) that are now buried down around 60-80 cms and also at about 110 cms. These layers have been unlikely to trigger by skiers, but they may still be sensitive to large loads like avalanches in motion or cornice fall.

Problems

Storm Slabs

A storm forecast for late Sunday will add to recent heavy accumulations. Watch for increased reactivity in wind-affected terrain.

Good day to make conservative terrain choices.>Be cautious as you transition into wind affected terrain.>Choose conservative lines and watch for clues of instability.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 5

Persistent Slabs

Storm loading has added additional stress to a persistent weak layer of surface hoar or a sun crust which now lie up to 100cm below the surface. Triggering this weakness may result in surprisingly large avalanches.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Avoid exposure to overhead avalanche terrain, as large avalanches may reach the end of runout zones.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 6

Valid until: Feb 24th, 2013 2:00PM