Avalanche Forecast

Issued: Feb 9th, 2013 9:04AM

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

Avalanche Canada swerner, Avalanche Canada

Intensity from the sun can make the snowpack weaken and avalanche danger rise rapidly. Be aware of this and keep travel options open to adjust with this change.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Sunday

Weather Forecast

Sunday: As the ridge shifts to the East, the region will remain under a NW flow which will keep alpine temperatures cooler but under high solar influence. However, some areas may still see high cloud cover through the day. Ridgetop winds will blow Light out of the North. Treeline temperatures around zero degrees and freezing levels rising to 1600 m.Monday: The dominating ridge will be to retreat to the South allowing a more zonal flow to set up off the coast. Ridgetop winds will switch and blow moderate from the NW. Treeline temperatures will be near -2 and freezing levels near 1100 m.Tuesday: A cold front embedded in the zonal flow will move through the region bringing moderate precipitation amounts accompanied by strong winds from the SW. Treeline temperatures will fall to -5 and freezing levels will be near 1200 m.

Avalanche Summary

Over the past couple of days a natural avalanche cycle was seen in some of the SE areas of the region. Crowns were 40-50 cm deep and avalanche size was 2-2.5. There was also a report of Natural Cornice fall triggering a slab size 2.5 on the slope below. This occurred on an East aspect and failing on the Jan. 23rd crust.

Snowpack Summary

20-40 cm of new snow is sitting on wind slabs and recently buried weak layers. Old storm snow has settled into a dense slab that sits on a persistent weak interface deeper (40-80 cm down) in the snowpack. Crusts, surface hoar and facets that were buried around January 23rd are acting as those weak interfaces. Use extra caution on large open slopes, cutblocks and convex rolls at and below treeline where buried surface hoar may be preserved.Wind slabs continue to develop and stiffen on lee slopes and behind terrain features like ridgelines and ribs. There is a lot of new snow out there available for wind transport.The mid-pack is generally well settled and strong and the average snowpack depth at treeline elevations is near 200 cm. Watch the duration and intensity of the sun in your local riding area, it may weaken the upper snowpack. Cornices have grown and could threaten the slopes below.

Problems

Wind Slabs

An icon showing Wind Slabs
Wind slabs continue to be a concern on lee slopes and behind terrain features like ridges and ribs. They could be triggered under the weight of a person. Looming cornices may threaten slopes below, especially if the sun comes out and the temps rise.
Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
New storm snow adds to the depth (50-80 cm) of the slab that is sitting on a variety of old surfaces comprising of surface hoar, crusts and facets. Persistent slabs continue to be reactive to rider triggers and can be difficult to predict.
Good group management is essential to manage current conditions safely.>Use extra caution on open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Feb 10th, 2013 2:00PM