Avalanche Forecast Northwest Coastal

Date Issued: Valid Until:

Avalanche Canada ghelgeson, Avalanche Canada

Avalanche Forecast

Fri Apr. 12th ยท 5:55PM

Alpine

Danger Ratings Considerable

Treeline

Danger Ratings Moderate

Below Treeline

Danger Ratings Low
Storm Slabs Storm Slabs

Alpine

Danger Ratings Considerable

Treeline

Danger Ratings Moderate

Below Treeline

Danger Ratings Low

Alpine

Danger Ratings Moderate

Treeline

Danger Ratings Moderate

Below Treeline

Danger Ratings Low
Watch for fresh slab formation, especially in high elevation north facing features as a storm rolls into the region. If storm totals exceed 30 cm, the danger ratings should all be bumped up one level.

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain on Saturday

Weather Forecast

The weather pattern looks more typically winter than we've seen in some time. Right now the weather models are in agreement that the region should receive 10 to 20 cm of convective snowfall on Saturday, even as far inland as Shames. Another 5 to 15 cm is possible Saturday night. There is a bit of a lull Sunday and Monday before another shot of precipitation looks to make landfall on Monday night.FRIDAY NIGHT: Freezing level around 1000 m, light generally west wind, 0 to 6 cm of snow possible. SATURDAY: Overcast, freezing level around 1200 m, moderate to strong south/southwest wind, 10 to 20 cm of snow.SUNDAY: Overcast with some clearing in the late afternoon, freezing level around 1000 m, light southwest wind, 0 to 4 cm of snow possible. MONDAY: Scattered cloud cover, freezing level rising to around 1400 m, light to moderate wind out of the south, trace of snow possible.

Avalanche Summary

On Thursday small loose wet avalanches were observed in steep terrain. Control work produced a few storm slab avalanches to size 2 on northeast facing slopes between 1800 and 2000 m.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

Storm Slabs

Storm Slabs

Up to 60 cm of snow has accumulated above a widespread crust and another 10 to 20 cm is possible Saturday. Watch for fresh slab development, especially in high elevation north facing features where human triggering is most likely near ridgecrest.

Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.Watch for changing conditions Saturday, storm slabs may become increasingly reactive.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Possible

Expected Size

1 - 2