Avalanche Forecast

Issued: Apr 8th, 2018 3:59PM

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

Avalanche Canada ghelgeson, Avalanche Canada

A buried persistent weak layer may roar back to life over the next few days as the freezing level rises and the sun comes out. South facing slopes are especially suspect and are best avoided at this time.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain on Monday

Weather Forecast

Monday, most of BC will receive partly cloudy conditions with a few lingering flurries in the Columbia mountains. A warm system makes landfall Tuesday morning, which should open the door to rain and wet snow into the alpine on Tuesday and Wednesday.MONDAY: Broken cloud cover, freezing level beginning around 1200 m rising to about 1800 m, light to moderate west/southwest wind, 1 to 4 mm of precipitation possible. TUESDAY: Scattered cloud cover, freezing level beginning around 1400 m rising to about 2500 m, light to moderate south/southwest wind, trace of precipitation possible.WEDNESDAY: Scattered cloud cover, freezing level beginning around 1500 m rising to about 1700 m, light to moderate southwest wind, 2 to 5 mm of precipitation possible.

Avalanche Summary

No new avalanche activity to report from Saturday.On Friday a size 1.5 persistent slab avalanche with a 60 cm crown was skier triggered on a north facing slope at 2000 m. Natural loose dry and loose wet avalanches were observed on north and west facing slopes above 2000 m.On Thursday warming temperatures initiated large loose wet avalanches to size 3 on south facing aspects between 2100 and 2700 m in the neighboring Glacier National Park. A small shallow wind slab was accidently triggered by a skier on a steep/unsupported east/southeast facing feature at 2200 m too.

Snowpack Summary

5 to 10 cm of new snow fell Saturday with moderate southerly wind. This snow rests on a crust that is present on all aspects below 2000 m, and extends up to about 2500 m on south facing aspects. The storm snow be be sitting on surface hoar on polar aspects (north and east) at upper elevations. The main concern is the mid-March Persistent Weak Layer (PWL) which is now 60 to 110 cm below the surface. This layer is composed of a crust on all aspects at low elevations. At upper elevations the layer presents as a crust on solar aspects (those that face south and west) and buried surface hoar on polar aspects. The reactivity of this interface has been steadily decreasing and while the likelihood of triggering a deeper persistent slab avalanche is lowering, the consequence of doing so remains high. Solar aspects are expected to be the most suspect as the freezing level begins to rise over the next few days.Deeper persistent weak layers from January and December are still being reported by professional observers, but are generally considered dormant.

Problems

Persistent Slabs

An icon showing Persistent Slabs
Weak crust and surface hoar 60 to 110 cm below the surface have shown prolonged reactivity since the last storm. South facing features have been the most reactive, a trend that is expected to continue as temperatures increase Monday and Tuesday.
Pay attention to overhead hazards like cornices which could trigger persistent slab avalanches.Use caution around sheltered steep or convex slopes where buried surface hoar may be preserved.Minimize exposure to steep south-facing slopes where recent storm snow overlies a crust.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Storm Slabs

An icon showing Storm Slabs
5 to 10 cm of snow fell Saturday with moderate southerly wind, which likely formed shallow wind slabs immediately lee of ridge crest. Warming temperatures and brief periods of sun Monday may initiate natural storm slab and loose avalanche activity.
Minimize exposure to steep, sun exposed slopes if the strong April sun comes out.Be cautious of sluffing in steep terrain.Be especially careful with wind loaded pockets near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 1.5

Valid until: Apr 9th, 2018 2:00PM

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