Avalanche Forecast

Issued: Feb 18th, 2019 4:09PM

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

Avalanche Canada shorton, Avalanche Canada

Triggering slab avalanches remains possible at all elevations and aspects. Carefully watch for signs of instability such as whumpfs and cracking.

Summary

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

MONDAY NIGHT: Cloudy with clear periods, moderate northwest wind, alpine temperatures drop to -15 C.TUESDAY: Cloudy with isolated flurries and trace accumulations, moderate northwest wind, alpine high temperatures around -10 C.WEDNESDAY: Cloudy with isolated flurries, light to moderate northeast wind, alpine high temperatures around -8 C.THURSDAY: Mostly cloudy, light north wind, alpine high temperatures around -10 C.

Avalanche Summary

Numerous skier triggered avalanches have been reported every day since Tuesday. Although most avalanches have been small (size 1-1.5), they have shown impressive propagation. Check some of the recent MIN reports for examples (here and here). On Sunday, freshly wind loaded features were very reactive to skier triggering, with a size 1.5 avalanches reported on convex features a variety of aspects. A few size 1.5 persistent slab avalanche were remotely triggered, primarily on south and east aspects at treeline. There were also several reports of whumpfing, indicating touchy persistent weak layers in the snowpack.

Snowpack Summary

Surface snow consists of a mix of low density snow and wind affected surfaces. 20 to 40 cm of snow from the past week is gradually settling, and in some areas has shown signs of becoming reactive above above a surface hoar and crust layer that was buried on February 7th. This layer is suspect at all elevations, particularly on wind loaded slopes and on steep south-facing terrain.Two other surface hoar layers are buried 50 to 80 cm deep the snowpack (referred to as the February 1st and mid-January layers). Although they have not been reactive recently, they are still being monitored by professionals. These layers are most prevalent below treeline on shady aspects. The lower snowpack is well settled.

Problems

Persistent Slabs

An icon showing Persistent Slabs
It remains possible to trigger an avalanche on one of the surface hoar or crust layers buried 30 to 80 cm deep. These layers are most prominent at treeline and below.
Use caution on open slopes and convex rolls Surface hoar distribution is highly variable. Avoid generalizing your observations.Caution around sheltered open areas at treeline and below including cutblocks, gulleys, and glades.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Wind Slabs

An icon showing Wind Slabs
Wind slabs can be found on a variety of aspects and at all elevations.
Wind from a variety of directions has formed wind slabs in unusual locations.Use caution in freshly wind-loaded features, especially near ridge crests.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Feb 19th, 2019 2:00PM