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Avalanche Forecast

Jan 17th, 2015–Jan 18th, 2015
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
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
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Sea To Sky.

This forecast assumes an intense storm overnight Saturday. If the storm fizzles, the danger ratings may be a tad too high.

Confidence

Fair - Intensity of incoming weather systems is uncertain on Saturday

Weather Forecast

Overnight Saturday, 20-40 cm snow is expected to fall above about 1000 m, with rain at lower elevations. This snow comes with strong SW winds. There's a possibility of a temperature spike during the storm, but weather models are not in agreement. By late Monday, precipitation and wind are expected to ease. Light snow is possible on Tuesday.

Avalanche Summary

Explosives and skiers triggered size 1-2 wind slabs on lee and cross-loaded terrain on Friday. I expect the size and likelihood of avalanches to increase overnight Saturday in response to snowfall and strong winds.

Snowpack Summary

Two recent pulses of snow accompanied by strong S-SW winds have built deep wind slabs above a hard crust and/or surface hoar. The buried crust is most pronounced between about 1500 m and 2200 m. The distribution of the surface hoar seems spotty across the region, but some operators found it to be widespread in their tenure before the snow began burying it. Where the surface hoar exists, whumpfing is already indicating the touchiness of this interface. Deeper snowpack weaknesses (curst/facet and/or surface hoar layers formed in November and December) have fallen off the radar, but they could be reawakened with a very heavy load (like a cornice fall or wind slab) in the wrong spot (like a thin snowpack area, or high elevation northerly aspects where there is no strong crust above).

Avalanche Problems

Wind Slabs

Deep wind slabs have built up over a weak crust/surface hoar interface.
Give cornices a wide berth when travelling on or below ridges.>Travel in alpine avalanche terrain is not advised without professional level safety systems and guidance.>

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

Elevations: Alpine, Treeline.

Likelihood: Very Likely

Expected Size: 1 - 5

Storm Slabs

In areas not affected by the wind, storm slabs may be lurking. These could be triggered by the weight of a person or snowmobile.
Choose well supported terrain without convexities.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 3