Avalanche Forecast

Issued: Mar 25th, 2015 9:17AM

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

swerner, Avalanche Canada

Cariboos.

A complex and unpredictable snowpack exists. Avalanche Canada has released a Special Avalanche Warning for this region. Check out the details here: http://www.avalanche.ca/news/VRHTjCUAADQcpVdL/spaw-150324

Summary

Confidence

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

Weather Forecast

A Pacific frontal system reaches the coast today and affects the Interior regions tonight through the forecast period. Warm air aloft will invade the region until Friday night with associated freezing levels near 2600 m. A trailing cold front will bring light precipitations and strong ridgetop winds. On Thursday, light precipitation amounts up to 5-15 mm is expected, ridgetop winds strong from the SW and freezing levels rising to 2500 m. On Friday, solar radiation could come into play with a mix of sun and cloud. Freezing levels steady at 2500 m and convective precipitation amounts from 2-8 mm. Unsettled conditions on Saturday will bring light precipitation amounts 5-10 mm, ridgetop winds moderate from the NW and freezing levels dropping to 2000 m.

Avalanche Summary

On Tuesday, the region continued to see numerous natural slab avalanches up to size 2.5 from all aspects and 2000-2500 m in elevation. Natural cornice failures up to size 2 were also reported from southeast aspects near 2600 m. Some of avalanches were failing on a crust layer from mid-March and also stepping down to a deeper crust/facet layer from mid-February. Human-triggered storm slabs and persistent slabs remain a serious concern, especially in steep alpine terrain. Remote triggering slab avalanches from afar also remain a concern. There is currently a Special Avalanche Warning for this region through the forecast period. For more technical information regarding the fatalities last weekend go here: old.avalanche.ca/cac/library/incident-report-database/view/12b2631a-5b7f-4f0e-a2d8-c6f89bfb494d

Snowpack Summary

At higher elevations, 40-60 cm of dense storm snow sits over the mid-March interface which had included crusts, wind affected surfaces, and/or old wind slabs. Anywhere from 25-60 cm of snow sits on the mid- March interface, which has recently been reactive as a storm slab. The mid- February persistent weak interface 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. Snow surfaces are reported to be moist below around 1900 m.

Problems

Storm Slabs

Storm slabs up to 25-60 cm thick may overlie a weak layer and remain reactive to human-triggering. These slabs may be moist or wet at lower elevations.

Avoid wind loaded features at upper elevations.>Use conservative route selection, stick to moderate angled terrain with low consequence.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

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 could easily 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

Rising freezing levels and an extended period of warm temperatures 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.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Mar 26th, 2015 2:00PM