Archived

Avalanche Forecast

Mar 30th, 2012–Mar 31st, 2012

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Northwest Coastal.

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.

Avalanche 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