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Avalanche Forecast

Dec 20th, 2017–Dec 21st, 2017
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Sea To Sky.

Strong northerly winds have redistributed the recent storm snow scouring windward areas and loading lee slopes.  These wind slabs may be easily triggered by a skier or rider.

Confidence

High - The weather pattern is stable

Weather Forecast

THURSDAY: Cloudy, flurries. Accumulation up to 5 cm. Ridge wind moderate from the west. Temperature -4. Freezing level 400 m.FRIDAY: Mix of sun and cloud. Ridge wind light from the northeast. Temperature -8. Freezing level 400 m.SATURDAY: Mainly sunny. Ridge wind moderate from the east. Temperature -8. Freezing level surface.

Avalanche Summary

Up to 20 cm of low-density snow fell on Tuesday, accompanied by moderate to strong northerly winds building reactive soft slabs 20-40cm thick. Numerous natural, skier controlled and skier remote storm slab avalanches to Size 1.5 were reported on various aspects at treeline and below running both within the storm snow as well as on the Dec 15th melt-freeze crust. See here for details in the Mountain Conditions Report. Ski cutting also produced a Size 2 storm slab avalanche in the alpine on Tuesday. And on Monday, we had reports of reactive wind slabs on steep north-facing slopes. See here for the MIN report.

Snowpack Summary

There is now 30-50cm of snow sitting on a melt-freeze crust that formed on all aspects and elevations in mid-December (December 15th layer). On high north aspects this crust is thin with dry, sugary snow crystals (facets) below.  Below the upper December 15th crust, the late November crust is now buried 70-100 cm with a thin layer of sugary snow (facets) above.  Beneath this crust the lower snowpack is well settled.

Avalanche Problems

Wind Slabs

Winds during and since the storm have been from the northwest - which is not the usual pattern.
Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3