Avalanche Forecast

Issued: Jan 4th, 2018 9:48PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Loose Wet, Storm Slabs and Wind Slabs.

Bill Phipps, VIAC

Vancouver Island.

Summary

Confidence

Moderate- few alpine but good treeline and below treeline observations, weather forecast models mainly in agreement.

Travel/Terrain Advice

Friday avoid exposure to terrain traps as wet loose slides tend to pack a punch. Stay away from gullies, and don't travel above cliffs, trees, rocks, and depressions that are exposed to large steep slopes above. Give avalanche paths and their runout zones a wide berth as wet sides tend to travel further than we expect. Sunday avoid convex, unsupported and steep open slopes in the alpine especially on north-west aspects where the wind will load start zones significantly. Take extra caution when moving up from one elevation band into the next.

Past Weather

No new snow in the forecast area with light-moderate (16-26 km/h) south to south east winds. Daytime temps were warm from 0 to 10 degrees in the alpine and treeline with cold temps only lingering near valley bottom. Light to moderate rain began late afternoon on Thursday all the way up into the alpine.

Avalanche Summary

No new avalanche activity was reported.

Snowpack Description

Surface - freezing levels and warm temps during the day have caused moist surface snow conditions on all aspect and elevations. Upper - Previous new snow has settled rapidly with the warm temps and is moist on all aspects and at all elevations. This snow is bonding well to the December 15 crust. Mid - Well settled. Snow pit tests produced only hard results on the mid November crust and concerns are limited even more by the bridging December 15 crust above. Lower - Well settled.

Weather Forecast

Warm temps, high freezing levels and rain Friday will begin to wain mid afternoon to the north and in the evening to the west and south. New snow will fall in the mountains late Friday and Saturday in light to moderate amounts. Saturday night-Sunday a new big system will arrive with strong south east winds and incredible new snow. Forecast amounts for this bulletin time frame show a potential of 14-50 cm of new. Yeah! Fri - 15-40 mm of rain tapering into 2-10 cm of new snow. Winds moderate-strong 20-50 km/h from variable directions. Freezing levels of 2400-750 m Sat - 2-10 cm of snow. Winds light early on from the west-south west, increasing to strong 40-50 km/h from the southeast, pushing our wonderful snow filled system our way Freezing levels of 500-800 m Sun - 10-30 cm of new snow. Winds strong south east tapering to light 45-13 km/h. Freezing levels of 550-900 m

Problems

Loose Wet

High freezing levels, warm temps and significant RAIN Thursday into Friday will weaken the upper snowpack and will almost certainly produce Loose Wet avalanches from sz 1-1.5 both with natural and human triggers. These will be possible at all elevations and aspects, but are more of a concern in the treeline and alpine. Luckily as we move into the weekend temps will drop, tightening the upper snowpack and precipitation will come in the form of snow, reducing this avalanche problem.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Certain

Expected Size

1 - 3

Storm Slabs

Snow will start to fall late Friday afternoon in north and Friday evening in the west and south. New snowfall amounts will be light at first (Friday and Saturday). Sunday will see moderate-heavy snowfall. This new snow will likely produce storm slabs with an avalanche size potential up to size 1.5-2 on all aspects in the alpine and treeline with a likelihood of triggering by human activity.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Wind Slabs

Strong south east winds will accompany Sundays new snow, forming wind slabs on north to west aspects in the alpine and exposed/open treeline. These wind slabs will have the potential to create avalanches up to size 2-2.5 and are likely-very likely to be triggered by people or naturally.

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

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 3

Valid until: Jan 7th, 2018 6:00PM