Avalanche Forecast

Issued: Apr 7th, 2015 10:29AM

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

ghelgeson, Avalanche Canada

Cariboos.

Warmth is the primary driver of avalanche hazard and the weather forecast calls for a steadily increasing freezing level over the next few days. Minimize your exposure to large slopes if the snowpack is becoming moist or wet.

Summary

Confidence

Fair

Weather Forecast

WEDNESDAY: Freezing level starting at 1400m, rising to 2000m. Light W/NW winds at all elevations. No significant precipitation expected. Clear skies.THURSDAY: Freezing level starting at 1500m, rising to 2200m. Light S/SW winds at all elevations. No significant precipitation. Clear skies.FRIDAY: Freezing level holding at 1800m. Strong south winds at treeline, strong to extreme south winds at ridgetop. Increasing cloud cover. No significant precipitation expected.

Avalanche Summary

No new observations from Monday. On Sunday a very large (size 3) deep persistent slab failed naturally on a steep glacial feature at 2500m. It's presumed that this failed on early season basal facets. A small natural cornice fall was also observed.

Snowpack Summary

Surface hoar is beginning to form on top of the 15-30cm of new snow that fell last weekend. This snow remains dry on high elevation polar aspects but is quickly turning moist everywhere else. Moist snow exists underneath this most recent storm snow in most of the region.Two significant persistent weak layers composed of crust and facets exist in the snowpack. Mid-March is down 40 to 80cm below the surface and Mid-February is down 80 to 200cm. Avalanche activity on these weak layers has tapered off, but snowpack tests indicate that these layers may still be sensitive to triggering. Down at the bottom of the snowpack a weak layer of basal facets exists. Large loads like cornice/ice fall or even sustained warming could initiate an avalanche on this very deeply buried weak layer.

Problems

Cornices

Steadily increasing temperatures over the latter half of the week will make cornices more prone to failure. While falling cornice is in itself problematic, this action could drive persistent slab release on slopes below.

When traveling in the alpine, be SURE you're on the ridge, and not on a cornice.>Cornices become weak with daytime heating, so travel early on exposed slopes.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

While the likelihood of triggering a large persistent slab avalanche has gone down, the consequences of human triggering remain high. It's tough to say which features harbor a trigger-able weakness and which don't with any amount of certainty.

Stick to well supported terrain while avoiding potential trouble areas like rock outcroppings, convexities, and spots where the snowpack goes from thick to thin.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 7

Loose Wet

Anytime previously dry/cool snow experiences the intense kiss of the spring sun, loose wet avalanches are likely. Increasing temperatures may even drive loose wet activity on high elevation north and east facing features as the week goes on.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Apr 8th, 2015 2:00PM