Avalanche Forecast

Issued: Jan 20th, 2018 4:30PM

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

Avalanche Canada cgarritty, Avalanche Canada

Winds are driving slab problems at higher elevations. Chances of triggering a storm slab or even a deeper persistent slab are increased at lower elevations.

Summary

Confidence

Moderate -

Weather Forecast

Saturday night: Flurries bringing approximately 5 cm of new snow. Moderate to strong southeast winds. Sunday: Cloudy with continuing scattered flurries bringing 2-5 cm of new snow. Moderate southeast winds. Alpine high temperatures around -7.Monday: Mainly cloudy with isolated flurries and a trace of new snow. Light to moderate southwest winds. Alpine high temperatures of -7.Tuesday: Mainly cloudy with flurries beginning in the afternoon. Moderate to strong southeast winds. Alpine high temperatures of -8.

Avalanche Summary

Reports from Friday show a notable increase in persistent slab activity at lower elevations in the Howson Range. In this area, three Size 2 releases failed on steeper terrain with remote (from a distance) triggers on the mid-December weak layer, found 50 cm below the surface. Reports from Thursday included one observation of numerous natural storm slab releases from Size 1-2 north of Kispiox. These were noted running on relatively low angle terrain and suspected to have released over a layer of surface hoar that may not be widely distributed. Another few Size 2 natural storm slab releases were noted in very steep north aspects around treeline elevations in the Howsons.Looking forward, our storm slab problem is diverging into more distinct wind slab problems at higher elevations and more isolated storm slab over surface hoar issues at mid elevations. Lower elevations have become an increasing concern in areas where the upper 50 cm of the snowpack has settled into a slab over the persistent mid-December weak layer.

Snowpack Summary

Snowfall from last week brought a variable 10-20 cm of new snow to the region. The new snow has buried a temperature crust that likely exists well into the alpine. There are also reports of more isolated pockets of surface hoar beneath the new snow at lower alpine and treeline elevations. This surface hoar is noted in our avalanche activity discussion for having produced numerous storm slab releases in a localized area after the storm ended. Below the new snow interface, deeper weak layers in the snowpack include a few crusts and surface hoar layers that formed in early January and December. Most recent reports suggest the snow is well bonded to these layers, but recent persistent slab activity over a surface hoar and facet 'combo' at low elevations suggests that a dangerous persistent slab problem may be developing as the mid and upper snowpack consolidate into a stiffer slab over this layer.

Problems

Storm Slabs

An icon showing Storm Slabs
Storm slabs have formed over widespread temperature crusts and more isolated pockets of surface hoar. Slabs are likely to be touchiest where surface hoar is buried as well as in the immediate lee of ridgecrests and exposed terrain features.
Avoid areas where the new snow feels stiff and slabby.Sheltered openings at mid elevations are likely areas for surface hoar to be preserved.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
Recent reports have shown touchy persistent slab conditions developing at lower elevations in deeper snowpack areas of the region. Avoid the trap of lowering your guard below treeline - especially around steep rolls in sheltered openings.
Touchy persistent slab conditions have recently been observed in the Howson Range.Watch for signs of instability such as whumpfing, or cracking at lower elevations.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1.5 - 2.5

Valid until: Jan 21st, 2018 2:00PM

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