Avalanche Forecast

Issued: Apr 6th, 2016 9:37AM

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

jlammers, Avalanche Canada

Northwest Coastal.

Extreme warming and solar radiation will drive the Avalanche Danger. Be alert to conditions that change throughout the day, and watch your overhead hazard. Very large avalanches may reach their run-out zones.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

A dry ridge of high pressure will bring mainly clear skies for Thursday and Friday. Increased cloud and isolated flurries are forecast for Friday evening and Saturday. The freezing level will spike to about 2800m on Thursday and then hover around 2400m on Friday and Saturday. Ridgetop winds will remain mainly light and variable.

Avalanche Summary

Stormy weather has limited avalanche observations, although I'm sure there was a decent round of natural storm slab activity in response to new snow and wind on Tuesday. As temperatures rise, cornice failures, loose wet, wet slab and isolated deep persistent slab avalanches should be on your radar.

Snowpack Summary

On Tuesday between 25 and 45cm of new snow fell with highest accumulations noted in the south of the region. Extreme westerly winds throughout the storm promoted continued cornice growth and created a widespread wind effect at higher elevations. About 35-60cm below the surface you'll find a widespread hard melt-freeze crust that formed as a result of last week's warm weather and more recent cooling. A few deeply buried weak layers exist within the snowpack including a widespread crust/facet layer buried in early February down around 1.5 m and weak basal facets at the bottom of the snowpack. The near-surface crust has dramatically limited the reactivity of these destructive old layers; however, they have the potential for isolated yet very large avalanches with forecast warming and solar radiation.

Problems

Loose Wet

Rising freezing levels on Thursday will promote loose wet avalanche activity, especially in steep sun-exposed terrain. Loose wet avalanches can entrain mass quickly and run long distances. Be alert to conditions that change throughout the day.

Wet sluffs may trigger deeper instabilities.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 4

Storm Slabs

In high elevation lee terrain hard storm slabs may remain reactive to light loads with the potential for wide propagations. In areas more affected by heat and sun, the new snow may react as a wet slab.

Be cautious as you transition into wind affected terrain.>Be aware of the potential for wide propagations due to the presence of hard windslabs.>Good day to make conservative terrain choices.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Cornices

Some cornices are the size of a bus. As temperatures rise and sunny weather makes a come-back, these monsters will become more likely to fail. A large cornice fall may be the trigger required to initiate destructive persistent slab avalanches.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Apr 7th, 2016 2:00PM