Avalanche Forecast

Issued: Feb 11th, 2018 4:45PM

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

mgrist, Avalanche Canada

Northwest Inland.

Strong winds have created touchy slabs at higher elevations. Be wary of persistent slabs lurking at lower elevations. 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

MONDAY: Increasing cloud in the afternoon. Ridge wind strong from the northwest. Temperature -10. Freezing level valley bottom with an above freezing layer between 1400m and 1900m.TUESDAY: Snow (5-10cm). Ridge wind strong, southwest. Temperature near -4. Freezing level 400 m.WEDNESDAY: Mostly sunny. Ridge wind moderate to strong from the north / west. Temperature -7. Freezing level valley bottom.

Avalanche Summary

On Saturday we received several reports of natural avalanches to size 3 (particularly on northeast facing slopes at higher elevations) as the winds picked up and slab avalanches ran surprisingly far. See this MIN post for more information. See here for a stunning photo of a large avalanche. Also on Saturday, explosives control produced size 2.5 avalanches in below tree line terrain north of Smithers. Farther south but also below treeline, skiers were able to trigger a size 2 persistent slab avalanche on a south facing sparsely treed (deciduous) slope just north of Hankin. See here for the MIN report.

Snowpack Summary

Strong north west winds picked up on Saturday, redistributing last week's storm snow and creating touchy wind slabs at higher elevations. A strong inversion also set up with tree line temperatures near 0 degrees and a thin crust formed on steep south facing slopes.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 tree ine 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

Wind Slabs

Strong northerly winds produced reactive wind slabs in exposed areas at tree line and above. Expect these slabs to be reactive to human triggering and keep in mind that a release may also step-down to a deeper layer buried in the snowpack.

Be aware of the potential for wide propagations.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: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

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 recently. 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 12th, 2018 2:00PM