Avalanche Forecast

Issued: Jan 15th, 2013 9:44AM

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

ccampbell, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Fair - Due to limited field observations

Weather Forecast

Wednesday: Moderate precipitation with 10-15mm of water equivalent and freezing levels dropping throughout the day to1000. Moderate southwesterly winds increasing throughout the day. Thursday: Continued moderate precipitation with another 10-15mm, freezing levels increasing to around 1200m and strong to extreme southwesterly winds. Friday: Precipitation and winds easing throughout the day with freezing levels around 1200m.

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

Recent temperature inversions and freezing rain at higher elevations has resulted in a thin surface crust in treeline and alpine areas, while surface facets and surface hoar are surviving in the cold air trapped in valley bottoms. Some higher elevations particularly in the eastern part of the region may have gotten a dusting of new snow, effectively protecting the surface hoar, before the freezing rain, which would have capped this potential future persistent weakness with a thin crust. Below this, weaknesses within the 30-60cm of well settled storm snow is 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 northwesterly winds have created new wind slabs in exposed lee and cross-loaded terrain. And forecast southwesterlies with are expected to load notheasterly aspects with added snowfall.

Be cautious as you transition into wind affected terrain.>Avoid freshly wind loaded features.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Persistent Slabs

Warm temperatures are expected increase the likelihood of triggering the late December persistent weakness.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 5

Valid until: Jan 16th, 2013 2:00PM