Avalanche Forecast

Issued: Feb 3rd, 2018 5:58PM

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

Avalanche Canada cgarritty, Avalanche Canada

Fresh storm slabs have formed over a weak and unstable snowpack. The continuing storm will keep the snowpack near a tipping point. Keep seeking out simple terrain that is free of overhead hazard.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Sunday: Mainly cloudy with scattered flurries bringing approximately 5 cm of new snow. Light variable winds. Alpine high temperatures around -10.Monday: A mix of sun and cloud. Light west winds. Alpine high temperatures of -11.Tuesday: Cloudy with flurries bringing 5-10 cm of new snow, increasing overnight. Light to moderate west winds. Alpine high temperatures of -5.

Avalanche Summary

On Saturday, a large persistent slab avalanche was remote triggered by a snowmobiler approaching a convex slope in the Allan Creek area. The crown fracture was over a metre deep. Two recent size 2.5 natural persistent slab avalanches that failed on the mid-December weak layer were observed at 1500-1700 metres in the Monashees just south of the region.Explosive control work on Thursday produced avalanches to size 2.5 failing on both the mid and early January interfaces. These avalanches ran on north, northeast, east and southeast facing features between 1600 and 2600 m. Reports from Wednesday showed numerous recent size 2-3 releases on all aspects at all elevations, with several avalanches that reached size 4. Subsequent explosives control yielded storm slab and wind slab releases from size 2-2.5 and persistent slab results generally from size 2.5-3. The early January persistent weak layer was named as the primary failure plane for persistent slab releases, although several larger releases stepped down to the mid-December layer.On Tuesday, a size 2.5 avalanche on a northeast facing slope at 1920 m resulted in a single fatality in Clemina Creek. More details available here.

Snowpack Summary

15-25 cm of new snow fell over the region over Thursday night and Friday, bringing recent storm snow totals to 40-80 cm. This snow sits on an unstable snowpack with three active weak layers we are monitoring:1) The first layer is found beneath the recent storm snow and is formed of a crust and/or surface hoar layer that was buried in mid-January. The surface hoar is up to 10 mm in size, found at all elevation bands and has been very reactive on north through east aspects between 1900-2600 m. 2) Deeper in the snowpack, the early-January persistent weak layer is found 60 to 120 cm below the surface. This layer has been reported as the most active persistent weak layer during a recent natural avalanche cycle that took place in the region. It has also been the most reactive to recent explosives control.3) Another weak layer buried mid-December consisting of a facet/surface hoar/crust combination is buried 110 to 160 cm deep. It has been most problematic at and below tree line. Many avalanches that failed at shallower weak layers 'stepped down' to this interface during the recent avalanche cycle and in recent explosives control.

Problems

Storm Slabs

An icon showing Storm Slabs
Friday's storm formed new storm slabs at all elevations and ongoing snowfall will continue to build and add mass to these slabs. The problem is especially concerning at alpine elevations where strong winds have made slabs extra thick and reactive.
Choose sheltered terrain where new snow hasn't been wind-affected.If triggered, storm slabs may step down to deeper layers and result in very large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5

Persistent Slabs

An icon showing Persistent Slabs
Several deeply buried weak layers are persisting in the snowpack and continue to produce very large avalanches - especially with heavy triggers. This is a time to carefully measure your exposure to avalanche terrain and to avoid overhead hazards.
Seek out low angle, low consequence terrain as well as terrain that has seen heavy traffic.Either avoid or space out and travel quickly through runout zones of avalanche paths.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2.5 - 4

Valid until: Feb 4th, 2018 2:00PM