Avalanche Forecast

Issued: Mar 30th, 2012 10:09AM

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

triley, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

A moist unstable southwest flow is expected to continue to bring another 5-10 mm of precipitation combined with moderate gusty winds overnight to coastal areas. A surface high pressure is forecast to follow on Saturday morning that should be a bit drier, but light precipitation is expected to continue for most of the day near the coast. The wind should swing to the southeast and become light with moderate gusts. The interior areas around Smithers should see some broken skies and sunny periods. Another broad low pressure is expected on Sunday that should bring some light precipitation to both the coast and the interior. The next major system is expected on Monday.

Avalanche Summary

A few large avalanches were reported from the highway corridors on Thursday. Some natural avalanches up to size 3.5 from the Bear Pass area, and some glide slab releases from lower elevations in other areas. Strong south winds in the alpine may have started a natural cycle on north 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 forming crusts on solar aspects at all elevations that become moist under sunny skies during the day. Melt conditions exist on all aspects below 1000 m, with no significant re-freeze. 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 very 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

Recent strong southerly winds developed windslabs at ridgetops. Forecast snow and gusty winds may continue to transport snow overnight.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

2 - 5

Loose Wet

Recent unsettled conditions combined with freezing levels that have not dropped below 1000 metres are creating an unstable snowpack below treeline. Pinwheels, moist snow, and natural avalanches are signs of increasing danger.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

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.

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Mar 31st, 2012 9:00AM