Avalanche Forecast

Issued: Apr 5th, 2016 9:17AM

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

jlammers, Avalanche Canada

Northwest Coastal.

Deep storm slabs have formed and forecast warming will create its own mix of avalanche problems. Watch for a wide range of conditions as winter and spring weather patterns collide.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Wednesday

Weather Forecast

On Wednesday expect 5-10cm of new snow, strong to extreme southwest winds and freezing levels climbing from 1500 to 1800m over the course of the day. On Thursday and Friday, a dry ridge of high pressure will bring mainly sunny skies. Freezing levels will sit at about 3000m on Thursday and then drop to 2000m on Friday.

Avalanche Summary

Stormy weather has limited avalanche observations, although I'm sure there has been a decent round of storm slab activity in response to new snow and wind. Human triggering of new storm slabs will remain a very real concern on Wednesday, especially with forecast snowfall and extreme winds. As temperatures rise, cornice failures, loose wet, wet slab and isolated deep persistent slab avalanches should be on your radar.

Snowpack Summary

On Wednesday, moderate to locally heavy snowfall (up to 45cm) formed deep new storm slabs. Extreme winds throughout the storm created a widespread wind effect at treeline and in the alpine and promoted continued cornice growth. The recent storm snow overlies a widespread melt-freeze crust that formed as a result of last week's warm weather and more recent cooling. The warm temperatures and sun over the last week woke-up deeply buried weak layers within the snowpack. These includes a weak crust/surface hoar layer which is buried down 40-60cm in the north of the region, a widespread crust/facet layer buried in early February down around 1m, a lingering surface hoar layer from January down over a meter, and weak basal facets at the bottom of the snowpack. More recent cooling has dramatically limited the reactivity of these destructive old layers; however, they may come back to life during future periods of warming, solar radiation, or heavy storm loading.

Problems

Storm Slabs

Heavy snowfall and extreme winds have formed dense storm slabs at treeline and in the alpine. Although they may have gained some strength, they have the potential for wide propagations and may remain sensitive to human triggering.

Good day to make conservative terrain choices.>Be aware of the potential for wide propagations due to the presence of hard windslabs.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Loose Wet

As temperatures rise on Wednesday, loose wet avalanches should be on your radar. If the sun makes an appearance, they will become very likely.

Wet sluffs may trigger deeper instabilities.>Avoid avalanche terrain during periods of rain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Cornices

Stormy weather has encouraged new cornice growth, and newly formed cornice tabs will be weak. If the sun makes an appearance, larger more destructive cornice falls will be possible.

Give cornices a wide berth when traveling on or below ridges. >Do not travel on slopes that are exposed to cornices overhead.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Apr 6th, 2016 2:00PM