Avalanche Forecast

Issued: Feb 9th, 2018 5:49PM

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

Avalanche Canada mgrist, Avalanche Canada

Avalanche danger will remain elevated due to warm temperatures on Saturday. Storm slabs remain primed for human triggering, especially in wind-loaded areas. Choose conservative terrain and be aware of overhead hazard, especially on sunny aspects.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

We're looking at a break from the stormy weather for the foreseeable future, but outflow winds will pick up by Sunday. It will be warm up high on Saturday.SATURDAY: Mostly Sunny. Ridge wind moderate to strong from the north west. Temperature near 0. Freezing level 1600 m.SUNDAY: Mostly sunny. Ridge wind moderate to strong from the north. Temperature -10. Freezing level valley bottom.MONDAY: Mostly sunny. Ridge wind light, northeast. Temperature -10. Freezing level valley bottom.

Avalanche Summary

Numerous natural storm slab avalanches up to size 2 were reported to be running in steep terrain during the storm on Wednesday in the southern part of the region. See here for a good summary of avalanche activity near Smithers. On Monday evidence of a natural avalanche cycle from size 1.5-2.5 was reported on north through south aspects between 1200-1600 m in the Howson Range failing both in the recent storm snow as well as the deeper mid-December layer. A natural size 2.5 that failed on a deep weak layer of sugary, facets at the base of the snowpack was also reported from the northern part of the region near Ningunsaw.Last week some large (size 2-3) natural persistent slab avalanches in the Howsons, and two large (size 2.5) remotely triggered avalanches north of Kispiox were reported. We have no information from the Smithers area, but suspect a similar deeper weakness could exist there too. Activity on buried weak layers is most suspect during periods of heavy loading or rapid warming, hence it's time to be cautious.

Snowpack Summary

Wednesday's storm delivered between 15-50 cm of new snow, bringing totals to 40-100 cm over the past week. Areas near Smithers and farther south saw higher snowfall amounts than areas to the north. A crust and/or weak feathery surface hoar layer buried in mid-January now lies about 100 cm below the surface. The crust exists well into the alpine and the surface hoar can be found in sheltered areas in the lower alpine and treeline elevations. Recent snowpack tests produced hard, sudden results on weak, sugary snow crystals associated with this crust in the Smithers area, indicating that this is still a layer of concern to watch for.Another two crust / surface hoar layers that were buried in December are now 100-150 cm below the surface. These layers produced sudden results in recent snowpack tests and have been the suspected weak layer in recent large remotely (from a distance) triggered avalanches.

Problems

Storm Slabs

An icon showing Storm Slabs
New storm slabs exist particularly at upper elevations and in wind-exposed areas. Expect these slabs to be reactive to human triggering and keep in mind that a release in the new snow may also step-down to a deeper layer buried in the snowpack.
Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.Avoid lee and cross-loaded terrain near ridge crests or convex rolls.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5

Persistent Slabs

An icon showing Persistent Slabs
Weak layers buried 100-150 cm below the surface have been reactive in recent snowpack tests and have also produced a few large avalanches last week. These layers may remain sensitive to human triggering in shallow snowpack areas.
Avoid shallow or thick to thin snowpack areas where triggering a deeper layer is more likely.Avoid lingering in runout zones, avalanches triggered up high may run long distances.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3.5

Valid until: Feb 10th, 2018 2:00PM

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