Avalanche Forecast

Issued: Feb 22nd, 2018 3:46PM

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

Avalanche Canada mconlan, Avalanche Canada

New storm slabs are forming, which may not bond well to underlying snow surfaces. Conservative decision making is recommended.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

FRIDAY: Cloudy with snowfall, accumulation 10 to 15 cm, strong westerly winds, treeline temperature -4 C, freezing level below valley bottom.SATURDAY: Cloudy with early-morning snowfall then clearing to mostly sunny, accumulation 5 to 10 cm, light northwesterly winds, treeline temperature -1 C, freezing level near 600 m.SUNDAY: Cloudy with early-morning snowfall, accumulation 15-25 cm, strong westerly winds, treeline temperature -1 C, freezing level near 500 m.

Avalanche Summary

On Tuesday and Wednesday, several natural wind slab avalanches were reported from all aspects up to size 2. Although a couple of them were recent, the bulk of them likely released on the weekend. Expect natural and human-triggered avalanche activity to increase with the incoming storms.

Snowpack Summary

New storm snow will fall on highly variable and wind-affected surfaces. In exposed terrain, strong north winds have scoured north facing slopes and produced wind slabs on southern slopes. In sheltered terrain, new snow will fall on last weekends storm snow. The new snow may not bond well to these surfaces and could be reactive to both natural and human triggers.A hard rain crust that extends into alpine terrain is buried about 40 to 70 cm. Reports suggest the snow has a poor bond to the crust with test results showing sudden planar characteristics, a Rutschblock 2 (the whole block failing after standing on it), and it remains reactive to human triggers. Monitor the bond of the snow to this crust closely. There are no substantial layers of concern below the crust.Also make note of cornices at ridgeline. Variable winds in the past month have produced cornices on all aspects, which will become touchier as they grow in size, temperatures rise, and the sun packs more of a punch. Stand well back of them!

Problems

Storm Slabs

An icon showing Storm Slabs
Storm slabs will form over the day with new snow and strong westerly winds. Expect deeper and touchy slabs in lee features. They sit above previous wind slabs that are not bonding well to a buried crust. Be cautious of cornice growth on ridges.
Use ridges or ribs to avoid pockets of wind-loaded snow.Watch for signs of instability, such as avalanche activity, whumpfs, and shooting cracks.Use caution above cliffs and terrain traps where small avalanches may have severe consequences.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5

Valid until: Feb 23rd, 2018 2:00PM

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