Avalanche Forecast

Issued: Dec 22nd, 2017 4:38PM

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

Avalanche Canada jmcbride, Avalanche Canada

Hazard ratings are for the southern part of the region where storm snow totals range from 80-100 cm. Northern areas that received lower snowfall amounts can expect the same avalanche problems with lower hazard ratings.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Sunday

Weather Forecast

SATURDAY: Sunny. Ridge wind light from the northeast. Temperature -10. Freezing level surface.SUNDAY: Mostly cloudy, flurries. Accumulation 5-10 cm. Ridge wind light from the southeast. Temperature -12. Freezing level surface. Strong outflow winds near coastal valleys.MONDAY: Mix of sun and cloud. Ridge wind light from the northwest. Temperature -10. Freezing level surface.

Avalanche Summary

There were no new reports of avalanches on Thursday although whumpfing in hard wind slabs on cross-loaded features at treeline was observed in the northern part of the region. On Wednesday the Coquihalla and Allison Pass areas saw numerous loose dry to Size 1.5, as well as slab and glide avalanches to Size 2 on steep, leeward terrain and smooth rock slabs. Reports from the northern part of the region indicated wind slab activity up to size 2 on north and west aspects in the alpine.In the southern part of the region classic signs of instability such as whumpfing and shooting cracks have also been reported here in the MIN.

Snowpack Summary

The recent storm snow has been redistributed by moderate to strong northerly winds in the alpine and exposed treeline areas, creating wind slabs in some areas and scouring others (particularly in the northern part of the region).The southern part of the region has seen impressive storm snow totals (80-100cm) since Sunday night, compared to northern areas of the region, which received 25-35cm. This new snow sits on crusts of variable thickness that formed on almost all aspects in mid-December (December 15th layer). On steep southerly aspects the crust is supportive, whereas on northerly aspects the crust is quite thin and variable. Beneath the December 15th layer the snowpack is well settled. The late November rain crust is now buried 50-80 cm in the northern part of the region and well over 1 m in the south.

Problems

Wind Slabs

An icon showing Wind Slabs
Outflow (northerly) winds have redistributed the recent storm snow building wind slabs on leeward slopes.
Watch for signs of instability such as whumpfing, or cracking. Be cautious as you transition into wind affected terrain.Caution in lee and cross-loaded terrain near ridge crests.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Loose Dry

An icon showing Loose Dry
It may be possible to trigger a storm snow release in steep or convex, non wind-affected areas.
Be cautious of sluffing in steep terrain.Use caution above cliffs and terrain traps where small avalanches may have severe consequences.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Dec 23rd, 2017 2:00PM

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