Avalanche Forecast

Issued: Feb 15th, 2018 5:03PM

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

jmcbride, Avalanche Canada

Northwest Inland.

Wind and new snow have created slabs at upper elevations. With buried weak layers in the snowpack a release near the surface has the potential to step down. Choose conservative, supported terrain and be cautious in windloaded areas.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

TONIGHT: Clear periods, light flurries. Accumulation up to 5 cm. Ridge wind west, moderate to strong. Temperature -9. Freezing level valley bottom.FRIDAY: Cloudy with sunny periods. Ridge wind light, northwest. Temperature -9. Freezing level 400 m.SATURDAY: Mix of sun and cloud. Ridge wind light to moderate, northeast. Temperature -10. Freezing level valley bottom.SUNDAY: Mix of sun and cloud. Ridge wind, light to moderate, north. Temperature -14. Freezing level valley bottom.

Avalanche Summary

On Wednesday widespread natural avalanche activity up to size 2 was reported on wind-loaded, leeward slopes as well as loose snow releases on steep solar aspects in the afternoon.During the long weekend when we received reports of continued natural wind slab activity near Smithers. See this MIN report from Sunday.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

About 10-20 cm of new snow and strong winds from a wide range of directions (mostly northwesterly) have scoured some slopes and created wind slabs up to 50 cm thick at tree line and above. In areas sheltered from the wind, you'll find 40-70cm of recent storm snow from the past week. 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 line elevations. 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 snowpack tests and have been the suspected weak layer in large remotely (from a distance) triggered avalanches.See here for a good summary of recent snowpack test results near Smithers.

Problems

Wind Slabs

Winds have formed 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.

Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.Avoid lee and cross-loaded terrain near ridge crests or convex rolls.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2.5

Persistent Slabs

Weak layers buried 100-150 cm below the surface have been reactive in 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 16th, 2018 2:00PM