Avalanche Forecast

Issued: Feb 19th, 2013 9:59AM

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

jlammers, Avalanche Canada

South Columbia.

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Wednesday: Mix of sun and cloud / Light north winds / Freezing level at 800mThursday: Light snowfall intensifying in the evening / Moderate south winds / Freezing level at 900mFriday: Heavy snowfall / Moderate to strong south winds / Freezing level at 1100m

Avalanche Summary

Explosives control produced a couple of size 2 avalanches in the region. I have limited info regarding these events. No other new avalanches were reported.

Snowpack Summary

Variable amounts of low density snow add to the recent storm slab that is between 20-50 cms across the region. These light accumulations may overlie wind slabs which formed a few days ago in the alpine and at treeline. The recent storm slab is expected to remain reactive where it is sitting on the weak surface hoar layer that was buried on February 12th. The recent storm slab has also been reactive on Southerly aspects where a sun crust formed during the period from February 8th-11th. Warming from solar radiation or future loading on the recent storm may cause another cycle of natural activity, or an increased sensitivity to human triggers. There are older weak layers 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

This storm slab is expected to continue to be reactive where it overlies a weak layer of surface hoar and sun crusts. Reactivity is likely to increase with exposure to solar radiation.

The recent snow will require several days to settle and stabilize.>Avoid sun exposed slopes when the solar radiation is strong.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 5

Wind Slabs

Recently formed wind slabs are hidden under a dusting of low-density snow. Watch for triggering in the lee of ridge crests and in gullies.

Be cautious as you transition into wind affected terrain.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 5

Persistent Slabs

There are older layers of buried surface hoar and crusts that are unlikely to be triggered by the weight of a skier or sledder, but may be triggered by large additional loads like cornice fall or a slab avalanche in motion.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely

Expected Size

3 - 6

Valid until: Feb 20th, 2013 2:00PM