Avalanche Forecast

Issued: Mar 27th, 2012 10:22AM

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

swerner, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Fair - Due to variable weather conditions

Weather Forecast

A series of Pacific frontal waves and upper troughs will bring continued unsettled weather through the forecast period. Light -moderate precipitation amounts can be expected daily. With fast moving systems, timing seems to be hard to pinpoint. A strong upper SW flow will provide warmer the normal temperatures, rising freezing levels in the afternoon, then falling during the night. Things should start to cool off significantly by Friday. Wednesday: Snow amounts 5-10 cm above 1100 m. Ridgetop winds moderate from the South. Freezing levels 1000-1500 m. Thursday/Friday: Moderate precipitation on Thursday, light-moderate for Friday. Ridgetop winds mod-strong from the SW. Freezing levels 1000 m, falling to 500 m.

Avalanche Summary

Most operations have reported very little avalanche activity within their tenures. Reports of glide cracks continue to widen on solar aspects. On Sunday natural cornice failures triggered slab avalanches up to size 2.5 on the slopes below. Unsettled weather conditions are forecast. It's important to pay attention to weather, and it's influence on the snowpack when recreating in your local mountains. I suspect the period will be fairly cloudy, but if periods of sun shine through, beware of solar aspects.

Snowpack Summary

Moderate to strong southeast winds have created wind slabs on opposite slopes and terrain features in the alpine, and treeline. Spring-like conditions have existed over the past several days. This has formed crusts on solar aspects at all elevations that become moist under sunny skies during the day. Melt-freeze conditions exist on all aspects below 1000 m. This has developed a well settled upper snowpack with no significant layers of concern. New surface hoar growth up to 10 mm has been reported on sheltered North aspects. Forecast snow may initially have a poor bond to these new surface forms (crusts, surface hoar). Below all this, down 60-120 cm exists a spotty surface hoar/ facet interface. Operations from the field noted no recent activity on this layer. I suspect it's becoming dormant, but would be suspicious of large triggers like cornice fall, or under the weight of a sled and it's rider in specific areas. Cornices in the region are reported to be very large and potentially unstable.

Problems

Wind Slabs

New wind slabs will form with forecast snow and moderate SW winds. These exist on lee aspects, and terrain features. Cracking and/or whumphing felt below you is a good indicator of unstable, wind effected snow.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Cornices

Cornices are reported to be very large and potentially unstable at this time. A cornice fall could be destructive by itself, and may also act as a trigger on the slope below.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 6

Loose Wet

Forecast mix sun and cloud could provide enough solar radiation to initiate loose wet avalanches on solar aspects. Snowballing, pinwheels, and moist surface snow are indicators of snowpack deterioration. Best to avoid slopes with these conditions.

Aspects: North, North East, East.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Mar 28th, 2012 9:00AM