Avalanche Forecast

Issued: Apr 11th, 2019 4:33PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Loose Wet.

swerner, Avalanche Canada

Northwest Coastal.

Recent storm snow and southwesterly wind has formed reactive wind slabs. Natural avalanche activity will increase when temperatures rise and the sun comes out. Especially in areas that have received new storm snow.

Summary

Confidence

Moderate -

Weather Forecast

The next pacific frontal system will reach the North Coast Friday night bringing cloud and precipitation through the weekend.FRIDAY: Mix of sun and cloud with alpine temperature high near 2 degrees and freezing levels 1300 m. Ridgetop wind gusty from the southwest.SATURDAY: Cloudy with snow amounts 10-15 cm. Alpine temperatures near -2 and freezing levels 1100 m. Ridgetop wind moderate to strong from the southwest.SUNDAY: Mostly cloudy with snow amounts 2-7 cm. Alpine temperatures near -3 and freezing levels near 1000 m.

Avalanche Summary

On Wednesday, reports indicated several natural slab releases and a cornice fall up to size 2.5. Skier triggered slab avalanches (remotely-from a far) were also reported up to size 1.5. We suspect these avalanches were primarily failing on the April 4th crust interface. Daytime warming produced loose wet avalanches on solar aspects up to size 2.

Snowpack Summary

Anywhere from 20-80 cm of recent storm snow sits above a weak layer buried April 4th. This layer consists of a 4 cm thick crust on all aspects and surface hoar/facets above the crust on northerly aspects. This layer has been reactive with the recent storm snow and fresh wind slabs will likely remain sensitive to human triggering through the weekend, especially on the higher elevation northerly aspects. Digging deeper, north facing alpine terrain also has a layer of facets down approximately 100 cm below the surface, but this layer has not been recently active and is likely trending towards dormancy.Below treeline the snowpack is isothermal and in some places below threshold throughout much of the forecast region.

Problems

Wind Slabs

Up to 60 cm of snow has accumulated above a widespread crust. Strong southerly winds have likely formed fresh slabs in high elevation north facing features. Human triggering is most likely in the immediate lee of ridgecrest.

Back off if you encounter whumpfing, hollow sounds, or shooting cracks.Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.

Aspects: North, North East, East, North West.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Loose Wet

Periods of sunshine may initiate a loose wet avalanche cycle in the new snow. The likelihood of loose avalanches increases as temperatures warm through the day and/or if the sun comes out for a period of time.

Loose avalanches may start small but they can grow and push you into dangerous terrain traps.A moist/wet snow surface, pinwheeling and natural avalanches all indicate a weakening snowpack.

Aspects: South East, South, South West.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Apr 12th, 2019 2:00PM