Avalanche Forecast

Issued: Jan 30th, 2016 3:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs, Cornices and Persistent Slabs.

pmarshall, Avalanche Canada

Sea To Sky.

The new snow may not initially bond well to the previous snow surface. Give the snow a day or two to settle before pushing into bigger terrain.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Tonight and Sunday: Periods of snow. 5-10 cm tonight and 15-20 cm on Sunday. The freezing level is around 600-800 m. Winds are moderate from the S-SW easing to light. Monday: Cloudy with flurries and clearing. The freezing level is around 500-700 m and winds are light from the SW. Tuesday: Mainly sunny. The freezing level remains near 500 m and winds are light and variable.

Avalanche Summary

A few natural size 2-3.5 persistent slab avalanches were reported near Whistler on Friday. Some may have started as loose wet slides that stepped down and triggered deep slabs. All of these slides were from slopes near treeline (1800-2000 m). These likely occurred during the height of the storm on Thursday night. Explosives control also produced numerous size 2 storm slabs. Cooler and drier conditions should help improve stability and make triggering much less likely.

Snowpack Summary

By Sunday morning there could as much as 40 cm of dry new snow with the snow line extending down to at least 800 m. Expect fresh wind slabs in exposed lee terrain and the potential for storm slabs or loose dry avalanches. The intense storm earlier this week dropped around 80mm of precipitation throughout the region with fluctuating freezing levels. In the alpine deep and dense storm slabs formed and there was substantial cornice growth. At and below treeline the new snow likely sits on a crust or moist/wet snow. Where it still exists, the mid-January surface hoar layer is between 100 and 180 cm below the surface. The combination of heavy storm loading and warm temperatures has likely flushed out this weak layer in most areas. There is still some uncertainty regarding the sensitivity and distribution of this persistent avalanche problem, especially at high elevations in the north of the region where it remains reactive in snowpack tests.

Problems

Storm Slabs

New snow may not bond well to the previous snow surface, especially in exposed lee terrain where wind slabs have developed. Also, watch for loose snow sluffing in steep terrain.

Avoid freshly wind loaded features.>Choose well supported terrain without convexities.>Be cautious of sluffing in steep terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Cornices

Recent stormy weather has encouraged widespread cornice growth. Cornice falls can be destructive by themselves, but can also be a trigger for surprisingly large avalanches on the slope below.

Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 4

Persistent Slabs

Buried persistent weaknesses may have been destroyed in most areas, but remain cautious in high elevation terrain (particularly in the north of the region) where this problem may be lingering.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Jan 31st, 2016 2:00PM