Avalanche Forecast

Issued: Jan 16th, 2013 9:00AM

The alpine rating is high, the treeline rating is high, and the below treeline rating is considerable. Known problems include Wind Slabs, Storm Slabs and Persistent Slabs.

Peter, Avalanche Canada

Northwest Coastal.

A strong storm should reach the northwest tonight. Some areas could see as much as 80 cm by Thursday night with strong to extreme winds. Probably worth waiting this one out!

Summary

Confidence

Fair - Track of incoming weather is uncertain

Weather Forecast

Synopsis: A strong frontal system pushing into the Northwest by Thursday. Precipitation amounts look heaviest close to the coast (Stewart, Bear Pass) but areas near Terrace should see at least moderate amounts. Overnight and Thursday: Moderate to heavy snow – 25-60 cm. The freezing level is around 800 m. Winds are very strong from the west-southwest. Friday: Cloudy with possible sunny breaks. The freezing level lowers to 500 m. Winds ease to moderate from the northwest. Saturday: Light snowfall. The freezing level is near valley bottom. Winds pick up again from the northwest.

Avalanche Summary

Recent reports include numerous natural moist slab avalanches up to Size 2.5 and widespread wet sluffing with warm temperatures and light rain on Monday. In the eastern part of the region, extreme winds caused numerous thin wind slab avalanches in alpine areas below ridgetops, and strong solar radiation caused a few Size 2 released right to the ground. On Sunday there was a report of a size 1.5 skier triggered avalanche on a steep unsupported convex roll on a northerly aspect. This event likely released on the late December surface hoar layer approximately 60 cm deep. There are also a few reports of glide releases in steep south facing terrain.

Snowpack Summary

Mild temperatures have resulted in moist snow below treeline, while strong or extreme upper winds have scoured areas and produced hard or soft wind slabs in a variety of areas at all elevations. Below this, weaknesses within the 30-60cm of well settled storm snow are only producing resistant fractures in recent snowpack tests. However, a persistent weakness of surface hoar or facetted snow buried at the end of December sits at the base of this recent storm snow and continues to react as sudden fractures in snowpack tests particularly below treeline. The mid and lower snowpack is generally well settled and strong, although well developed basal facets remain a concern in shallow snowpack areas.

Problems

Wind Slabs

Strong to extreme westerly winds have likely created touchy hard and soft wind slabs in exposed lee and cross-loaded.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

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

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 5

Storm Slabs

Storm slabs will build on Thursday and may not bond well to the underlying snow surface.

Stick to non-avalanche terrain or small features with limited consequence.>Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 4

Persistent Slabs

Heavy loading by new snow and wind may overload the late December persistent weakness and result in large and destructive avalanches.

Avoid exposure to overhead avalanche terrain, as large avalanches may reach the end of runout zones.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 6

Valid until: Jan 17th, 2013 2:00PM