Avalanche Forecast

Issued: Feb 3rd, 2013 9:50AM

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

mpeter, Avalanche Canada

Northwest Coastal.

There is dramatic variability across the region, and this forecast represents the areas hardest hit by the recent storms.

Summary

Confidence

Fair - Due to limited field observations

Weather Forecast

Monday: Expect a lull in the storm activity, with cloudy skies, light variable winds and alpine temperatures reaching -6. No precipitation.Tuesday & Wednesday: Several weak disturbances should make their way across the region, giving isolated bursts of precipitation under consistent cloudy skies. Expect light to moderate southerly winds and alpine temperatures should reach -5 each afternoon.

Avalanche Summary

Avalanche activity has picked up over the last couple days with the increase in load and temperatures. Many loose wet avalanches up to size 2.0 have occurred below treeline, where the recent precipitation has fallen as rain. Higher in the terrain both explosive and rider controlled triggering has been observed, predominantly in wind loaded areas. A single, large, cornice triggered natural was reportedÂ (size 3.0) on a north facing slide path in the Bear Pass region.

Snowpack Summary

Up to 40mm of water equivalency has fallen in the past 24-36hrs. Below 1000m, much of this precip has fallen as rain and we have reports in some areas that the upper 50cm of the snowpack is rain soaked. Above 1000m, the new snow is settling rapidly. Windslabs are forming in lee zones and behind ridges with the consistent SW winds. Cornices are growing rapidly under the current condition.A thin melt-freeze crust buried on January 17 is widespread at lower elevations. The combo of rainsoaked surface snow and this slick sliding layer may magnify the loose sluffing at lower elevations in the short term.Lingering deeper (down 50-80 cm) sits a persistent weakness comprising of surface hoar and/or facets. Recent tests on this layer are showing both sudden and resistant planar results. We have also seen an extended column test at 30/100 (end) indicating the propensity for propagation if this layer were triggered.Â Keep these layers on your radar in regards to distribution and reactivity. The mid and lower snowpack is generally well settled and strong, although basal facets remain a concern in the northern part of the region.

Problems

Storm Slabs

Some areas may have 50 cm of recent storm snow. SW winds have built fresh windslabs in lee features and behind ridgecrests. Warm temperatures have promoted rapid settlement and slabbing in open areas. Wet Slabs are possible at lower elevations.

The new snow will require several days to settle and stabilize.>Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Persistent Slabs

Up to 80 cm sits above a persistent weakness comprising of a facet/surface hoar interface above 1000m and a crust below 1000m. The rain soaked surface snow at lower elevations will be particularly reactive.

Dig down to find and test weak layers before committing to a line.>Watch for wet loose or slab activity with forecast rain and/or warm temperatures.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Cornices

The recent weather was prime for cornice growth.

Extra caution needed around cornices with current conditions.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 6

Valid until: Feb 4th, 2013 2:00PM