Avalanche Forecast

Issued: Feb 24th, 2016 7:55AM

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

rbuhler, Avalanche Canada

South Columbia.

The snowpack is complex and quite variable right now. Buried weak layers remain reactive and conservative terrain selection remains critical. Extra caution is required during the heat of the day, especially on sun exposed slopes and around cornices.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

A ridge of high pressure keeps the region dry Thursday and Friday before a weak storm system arrives Saturday. Thursday is expected to be mainly sunny with light alpine winds from the southwest to west. Freezing levels are expected to drop below valley bottom overnight and reach 1700-2000m on Thursday afternoon. Friday is expected to be mainly sunny in the morning with increasing cloudiness during the afternoon. Alpine winds are expected to be light from the southwest but may increase during the afternoon and freezing levels are forecast to reach 2000-2500m. There is still a lot of uncertainty as to how warm it will get on Friday. A weak storm front is currently forecast to reach the region Friday overnight bringing 5-15cm of snowfall on Saturday.

Avalanche Summary

On Tuesday, numerous natural and skier triggered avalanches were reported.Â Natural activity includes one size 1.5 storm slab from a northeast aspect around 1900m and lots of size 1-2 loose dry avalanches from steep and rocky sun-exposed terrain.Â A large cornice released naturally as well as a piece of glacier ice.Â A skier triggered a size 1.5 loose dry avalanche which ran 200m.Â Ski cutting triggered several size 1 wind slabs on east-southeast aspects at 2200m which were typically 10cm thick.Â One size 1.5 wind slab was ski cut on a northeast aspect at 2150m which was 20-30cm thick. Explosives triggered several large cornices as well as some slabs 20-35cm thick. On Monday, numerous size 1-2 natural and human-triggered avalanches were reported in the region. This included storm slabs, wind slabs, cornices, and persistent slabs releasing on the early February surface hoar layer.

Snowpack Summary

New surface hoar growth is being reported on all aspects and elevations up to 10mm and a sun crust has formed on steep south facing slopes.Â A weak layer of surface hoar and/or a sun crust can be found 15-60cm below the surface.Â This layer is reported to be increasing in reactivity in the deeper snowfall areas as the recent low density storm snow continues to settle into a cohesive slab.Â The surface hoar and/or crust layer from early February is now down 60-100cm and has been responsible for some very large avalanches recently. This layer is expected to become most reactive during the heat of the day, especially on sun exposed slopes. Large cornices remain a concern and will become weak with daytime warming.Â

Problems

Persistent Slabs

A weak layer of surface hoar and/or a crust down 60-100cm remains susceptible to large triggers such as cornice falls or smaller avalanches stepping down. Wide fracture propagations are likely.

Caution around convexities or areas with a thin or variable snowpack.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Minimize exposure to sun exposed slopes when the solar radiation is strong.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 5

Storm Slabs

Lingering storm problems remain sensitive to human and solar triggering. This includes storm slabs over a layer of surface hoar in deep snowfall areas, old wind slabs in the alpine, and sluffing from steep sun exposed slopes during the afternoon.

Avoid steep sun exposed slopes when the solar radiation is strong. >Use increased caution in deeper snowfall areas where recent storm snow is settling into slabs. >Be cautious as you transition into wind affected terrain. >

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3

Cornices

Large and fragile cornices are will likely continue to fall of ridge crests with sun exposure and temperature fluctuations. Not only are they a hazard in themselves, but also a heavy trigger for slabs on the slope below.

Cornices become weak with daytime heating. >Extra caution needed around cornices with current conditions.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 5

Valid until: Feb 25th, 2016 2:00PM