Avalanche Forecast

Issued: Jan 15th, 2018 5:33PM

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

simonhorton, Avalanche Canada

Lizard-Flathead.

Avalanche conditions are still very dangerous! It's hard to have any confidence traveling in the backcountry with such a complex snowpack and sustained warming.

Summary

Confidence

Weather Forecast

TUESDAY: Increasing cloud throughout the day, moderate southwest winds, mild inversion with alpine temperatures hovering around 0 C.WEDNESDAY: Light flurries in the afternoon, strong southwest winds, alpine temperatures around - 2 C.THURSDAY: 5-10 cm of new snow, strong southwest winds, alpine temperatures around -5 C.

Avalanche Summary

On Monday, a few solar triggered avalanches (up to size 2.5) were reported in steep terrain. A small wind slab (size 1.5) was also reported on a northeast alpine feature. On the weekend, explosive testing produced several large persistent slab avalanches on deep weak layers, including a size 3.5 persistent slab that failed on the November crust. This avalanche ran nearly 800 m and exceeded the path's historic runout distance. Very significant avalanche activity occurred in the region last week, and the potential for more large avalanches remains.

Snowpack Summary

Warm alpine temperatures are rapidly settling recent storm snow as well as forming moist snow on solar aspects. More importantly, warming is stressing deeper layers in the snowpack. The early January surface hoar layer is roughly 60 cm below the surface and the unstable weak layer from mid-December (predominantly surface hoar and/or a sun crust) is found roughly 100 cm below the surface at treeline and below treeline elevations. Below, a rain crust that developed late-November with associated sugary facets is also being stressed. Snowpack test results show sudden fracture characters and high propagation potential for all of these buried layers, indicating that they can be triggered and could propagate into large, destructive avalanches.

Problems

Persistent Slabs

Large avalanches are being triggered on a number of buried weak layers, even in fairly dense trees and shallow slope angles, including remotely triggered slides. These layers are touchy and can produce very large, destructive avalanches that run far.

Avoid lingering or regrouping in runout zones.Minimize exposure to steep slopes on warm or sunny days.Be wary of slopes that did not previously avalanche - even on low angle terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 4

Wind Slabs

Variable winds have redistributed loose snow into wind slabs around ridge crests and exposed terrain features. A small wind slab release may provide enough stress to trigger a deeper persistent weak layer.

Be increasingly cautious as you transition into wind affected terrain.Use ridges or ribs to avoid pockets of wind loaded snow.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Jan 16th, 2018 2:00PM