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Archived

Avalanche Forecast

Dec 17th, 2017–Dec 18th, 2017
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
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
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Kootenay Boundary.

UPDATE: MONDAY DEC 17th @ 9amSignificantly more snow fell on Sunday night than was forecast. The combination of new snow, strong winds anda buried weak layer are a recipe for elevated danger ratings.

Confidence

Low - Due to the number of field observations

Weather Forecast

Monday will see lingering flurries before significant precipitation arrives on Tuesday.MONDAY: Cloudy with isolated flurries. Accumulation of 5-10 cm possible. Ridge wind moderate from the west. Temperature near -5. Freezing level 700 m.TUESDAY: Snow. Accumulation 20-35 cm. Ridge wind moderate from the southeast. Temperature near -7. Freezing level 500 m. WEDNESDAY: Clearing in the afternoon. Ridge wind moderate northerly. Freezing level at the surface.

Avalanche Summary

Early Monday morning we had reports small Size 1 storm slab avalanches being triggered off small features. A more widespread avalanche cycle is expected on Monday with significant wind-deposited snow amounts sitting on a weak surface hoar layer in many locations.

Snowpack Summary

UPDATE: MONDAY DECEMBER 17th @ 9am:Some areas saw 20-30 cm of new snow in Sunday night's storm, with moderate to strong winds. Snow drifts as deep as 60cm have been reported. This new snow has fallen on a variety of old snow surfaces, depending on aspect and elevation. On solar aspects a thin melt-freeze crust has been buried. On northerly aspects, feathery, surface hoar crystals (10-60 mm in length) have been buried below treeline as well as protected areas at treeline. In the alpine the old surface consisted of sugary snow (facets) and hard, wind scoured snow. Below the snow surface the upper snowpack is well settled and overlies a series of late-November crusts, now buried 20-50 cm and 15-25 cm thick. Recent snowpack tests have produced hard, resistant compression test results within the layers of this crust. Below the crust layer the lower snowpack is moist and well settled.

Avalanche Problems

Storm Slabs

Significantly more snow fell Sunday night than was forecast. Conditions are expected to be very touchy with the new snow sitting on a weak surface hoar layer in many locations.
Use conservative route selection, choose moderate angled and supported terrain with low consequence.Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of runout zones.Be aware of the potential for wide propagations.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 3