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Avalanche Forecast

Archived

Dec 20th, 2017–Dec 21st, 2017

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Coast Inland.

The recent storm snow will take some time to settle and stabilize. Until then make conservative terrain choices and watch for additional loading from wind on leeward areas.

Confidence

Moderate - The weather pattern is stable

Weather Forecast

THURSDAY: Cloudy, flurries. Accumulation up to 5 cm. Ridge wind moderate to strong from the west. Temperature -4. Freezing level 400 m.FRIDAY: Mix of sun and cloud, light flurries. Accumulation trace. Ridge wind light from northeast. Temperature -8. Freezing level 200 m.SATURDAY: Mainly sunny. Ridge wind light from the northeast. Temperature -10. 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.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 southern part of the region has seen impressive storm snow totals (80-100cm) since Sunday night, compared to the north 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 40-50 cm in the northern part of the region and closer to 1 m in the south. Treeline snow depths are approximately 1.4 m throughout the region.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.