Avalanche Forecast

Issued: Dec 21st, 2017 4:14PM

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.

jmcbride, Avalanche Canada

South Coast Inland.

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 (25-35 cm) can expect the same avalanche problems with lower hazard ratings.

Summary

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

FRIDAY: Mix of sun and cloud, light flurries. Accumulation trace. Ridge wind light to moderate from the northeast. Temperature -10. Freezing level surface.SATURDAY: Mostly sunny. Ridge wind light from the northeast. Temperature -10. Freezing level surface.SUNDAY: Cloudy, flurries. Accumulation up to 5 cm. Ridge wind light from the southeast. Temperature -12. Freezing level surface.

Avalanche Summary

The Coquihalla and Allison Pass areas reported 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 on Wednesday, while reports from the northern part of the region indicated wind slab activity up to size 2 on north and west aspects in the alpine.On Tuesday the northern part of the region saw several skier controlled avalanches to Size 1 in both hard and soft wind slabs at treeline as well as significant wind loading (up to 60 cm) and cracking on open slopes.In the southern part of the region no new avalanches have been observed, however classic signs of instability such as whumpfing and shooting cracks have 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 and has not been showing any signs of activity on the late November rain crust which is now buried 50-80 cm in the northern part of the region and well over 1 m in the south.

Problems

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. Choose moderate angled and supported terrain with low / no consequence.If off-trail travel is deep and punchy, avoid avalanche terrain, including runouts.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Loose Dry

It may be possible to trigger a storm snow release in steep or convex, non wind-affected areas.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 22nd, 2017 2:00PM