Avalanche Forecast

Issued: Feb 13th, 2017 4:42PM

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

Avalanche Canada cgarritty, Avalanche Canada

Warm temperatures are set to undermine stability over the coming days. The strength of our storm slab will be tested on Tuesday. Don't let the sunny weather lure you into inappropriate terrain.

Summary

Confidence

Moderate -

Weather Forecast

Tuesday: Sunny with cloudy periods. Winds light to moderate from the southwest. Freezing level to 3400 metres with alpine temperatures around +5.Wednesday: Mainly cloudy. Winds strong gusting to extreme from the southwest. Freezing level dropping from 3000 to 2000 metres with alpine temperatures around +4.Thursday: Flurries bringing about 5 cm of new snow. Winds strong gusting to extreme from the southwest. Freezing level around 2000 metres with alpine temperatures of +2.

Avalanche Summary

Sunday's reports are limited to a single MIN post revealing an impressive Size 3 avalanche in the Little Sands area. This avalanche -along with a number of others observed the same day- appears to have been triggered by solar warming. While the age of the avalanche in the photo is uncertain, backcountry travelers should be ready for ongoing warming to produce these types of avalanches over the coming days.Before this warming took effect, explosives control work in the Fernie area on Saturday yielded a few results up to to Size 1 within wind-affected surface snow. Friday's control work produced numerous storm slab results generally from Size 2-2.5 with two Size 3 results generating from storm loaded north to northeast aspects.

Snowpack Summary

Strong ridgetop winds have led to roughly 10 cm of wind scoured and pressed new snow at the surface, leaving very little in the way of ski penetration at treeline and above. Below around 1700 metres, the supportive, wind-affected snow gives way to a breakable rain crust. Beneath these variable surfaces lies an estimated metre of storm snow from storms over the past two weekends. The upper half of this layer was deposited as heavy, moist snow, while the lower half is considerably drier and less dense. This 'upside down' storm snow layer lies above a range of previous surfaces that includes wind affected surfaces, a layer of surface hoar in sheltered areas, facets, and/or a thin sun crust. The bond between this earlier storm snow and the old surface is suspected to be improving slowly while hard conditions at the current surface may be diminishing the effect of human triggering. The mid and lower snowpack are generally well settled and stable but isolated basal weaknesses may exist in shallow snowpack areas.

Problems

Storm Slabs

An icon showing Storm Slabs
Most of our upper snowpack is essentially a storm slab. Its bond to the underlying snow is improving, but elevated freezing levels will promote instability on each day of the current forecast period.
Use conservative route selection, choose low angled and supported terrain with low consequence.Minimize exposure to sun exposed slopes when the solar radiation is strong.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

Wind Slabs

An icon showing Wind Slabs
Strong winds have been redistributing new snow at the surface into thin wind slabs in lee areas. Solar radiation and warming temperatures will make these fresh wind slabs especially touchy.
Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Loose Wet

An icon showing Loose Wet
Warm temperatures will promote loose wet avalanches on Tuesday, especially in steep terrain. This problem will present at higher elevations as the freezing level rises.
Be cautious of sluffing in steep terrain.Use extra caution on solar slopes or if the snow is moist or wet.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Feb 14th, 2017 2:00PM