Avalanche Forecast

Issued: Feb 21st, 2016 7:37AM

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

Avalanche Canada pmarshall, Avalanche Canada

Small weather inputs (sun, snow, or wind) could make buried persistent weaknesses more reactive to human triggering. Conservative terrain choices are essential.

Summary

Confidence

Moderate

Weather Forecast

Monday: Cloudy with flurries in the morning and sunny breaks in the afternoon. The freezing level is around 1500 m and ridge winds are light from the NW. Tuesday: Mainly sunny. The freezing level is around 1500 m and ridge winds are light from the W-SW. Wednesday: Mainly sunny. The freezing level is around 1600 m and ridge winds are light to moderate from the W-SW.

Avalanche Summary

Several size 1 loose wet and loose dry avalanches were reported on steep slopes on all aspects on Saturday. Specific wind loaded features were also reactive to skier testing, generally producing size 1-2 slabs. There was also a report of a size 1.5 snowmobile triggered slab avalanche from a treeline feature in the Southeast corner of the region on Saturday. Throughout last week there were reports of natural and human triggered slab avalanches up to size 3 each day, with a fairly widespread natural avalanche cycle observed on Thursday and Friday.

Snowpack Summary

Expect the surface to be a mix of dry snow on shady slopes, wind-affected snow in exposed terrain, and a sun crust/moist snow on solar aspects depending on the time of day. 60-90 cm of settled storm snow sits on a melt-freeze crust. In some areas there is a weak layer of surface hoar at the interface between the storm snow and the crust. The bond between the crust or surface hoar remains suspect, but there are also weaknesses reported within the top layers of the recent storm snow. Moderate winds have created areas of wind slab in the lee of west or southwest winds that may be close to a metre deep. Wind slabs in motion may trigger the persistent weak layer on the crust and result in wide propagations and very large avalanches. Surface hoar buried in early January now lies up to 200cm below the surface and has become less of a concern. Possible triggers for this deep and destructive layer include a large cornice fall, strong sunshine, or significant warming.

Problems

Persistent Slabs

An icon showing Persistent Slabs
The February 10th surface hoar continues to allow for long fracture propagations resulting in very large avalanches. Strong solar may increase likelihood of triggering.
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Choose conservative lines and watch for clues of instability.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 5

Storm Slabs

An icon showing Storm Slabs
Weak bonds may exist within the recent storm snow. Storm slabs in motion may step down to the persistent weak layer resulting in very large avalanches. 
Be cautious of sluffing in steep terrain.>Avoid freshly wind loaded features.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Cornices

An icon showing Cornices
Natural cornice falls may trigger storm slab avalanches on the slopes below. Periods of strong solar radiation may increase the likelihood of natural cornice falls.
Extra caution needed around cornices with current conditions.>Cornices become weak with daytime heating. >

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Valid until: Feb 22nd, 2016 2:00PM