Avalanche Forecast

Issued: Mar 27th, 2015 9:25AM

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

swerner, Avalanche Canada

Cariboos.

A complex and unpredictable snowpack exists. Continued warm temperatures, rain, and periods of sunshine will create the perfect recipe for avalanches. Avalanche Canada has released a Special Avalanche Warning for this region.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

An unsettled, winter-like weather pattern will continue through the forecast period. A weaker storm will make way to the Interior tonight and freezing levels will drop significantly in the wake of the cold front. As the front sweeps through, light-moderate precipitation will fall and ridgetop winds will be moderate from the west. On Saturday and Sunday, accumulated precipitation 5-25 mm with ridgetop winds blowing strong from the west and freezing levels steady around 2000 m. The general weather pattern is expected to bring multiple systems but the confidence in the exact timing, track, and strength of each system is poor.

Avalanche Summary

In the Cariboo region no new avalanches were reported on Thursday, however; in the North Columbia Mountains south of the Cariboo's, warm, wet and windy weather was responsible for a widespread natural avalanche cycle up to size 3. With similar weather conditions, I'd hedge my bets that this was also the story in the Cariboo's. I suspect natural avalanche activity will likely continue with warm temperatures, strong winds and periods of sun and rain. Avalanches failing on the persistent interface will be large and destructive.

Snowpack Summary

A rain soaked upper snowpack exists to 2000 m. Above that elevation, new, dense storm snow (25 cm) has added load over the mid-March interface 40-60 cm down. This interface is comprised of a series of crusts, wind affected surfaces, and old wind slabs Digging deeper is the mid- February persistent weak interface which is now down 80-120 cm and continues to be very reactive, producing very large and destructive avalanches. In exposed terrain, strong SW winds had redistributed the new snow into wind slabs on leeward features.

Problems

Persistent Slabs

The persistent weak layer buried mid-February is down up to 80-120 cm below the surface and has been the culprit of many large avalanches recently. Smaller avalanches and cornice failures could easily trigger slabs that step down to this layer.

Be aware of the potential for wide propagations and remote triggering from far distances away.>Avoid convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

3 - 6

Loose Wet

Warm temperatures and periods of sunshine will likely deteriorate the upper snowpack, resulting in loose wet avalanche activity.

Watch for clues, like natural avalanche activity, sluffing off of cliffs, moist/ wet snow surfaces, and snowballing. These are indicators that the snowpack is warming up and deteriorating.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Valid until: Mar 28th, 2015 2:00PM