Avalanche Forecast

Issued: Apr 8th, 2015 10:05AM

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.

Direct sun & warmth are currently the primary drivers of hazard and the weather forecast indicates that Thursday will be quite warm. Minimize your exposure to large slopes if the snowpack becomes moist or wet.

Summary

Confidence

Fair

Weather Forecast

THURSDAY: Freezing level starting at 1500m, rising to 2100m. Initially calm, winds increasing in the afternoon to Light S/SW winds at treeline, Moderate S/SW winds at ridgetop. No significant precipitation. Clear skies.FRIDAY: Freezing level holding at 1800m. Strong south winds at treeline, strong to extreme SW winds at ridgetop. Increasing cloud cover. No significant precipitation expected.SATURDAY: Freezing level hovering around 1500m. Scattered flurries, less than 5cm of snow expected. Moderate SW winds at treeline, strong SW winds at ridgetop. Overcast.

Avalanche Summary

On Tuesday cornice failure triggered a size 3 avalanche on a North facing feature at 2700m. 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.

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

Thursday looks to be the warmest day in recent memory. As the mercury rises cornices become more prone to failure. While falling cornice is in itself problematic, this mechanism could drive persistent slab release on slopes below.

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

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 5

Persistent Slabs

It's tough to say which features harbor a trigger-able weakness and which don't with any amount of certainty, but cornice fall driven by warm temperatures is the most likely trigger.

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

Loose avalanche activity should peak Thursday as the freezing level creeps well into the alpine. Loose wet avalanches are possible on all aspects. While slow moving, these avalanches can be very powerful and you do not want to be caught by one.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Apr 9th, 2015 2:00PM