Avalanche Forecast

Issued: Feb 24th, 2017 3:54PM

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

Avalanche Canada triley, Avalanche Canada

Weak sugary facetted snow in the bottom third of the snowpack continues to be a concern for triggering large avalanches.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Sunday

Weather Forecast

Tonight: Overcast with light west winds, flurries, and alpine temperatures -15. Saturday: Overcast with light snow and periods of intense flurries. Expect 3-5 cm of new snow combined with moderate westerly winds. Sunday: Overcast with light easterly winds and 5-8 cm of new snow, and alpine temperatures -15. Monday: Overcast with flurries and southerly winds.

Avalanche Summary

The recent storm snow has not settled into a cohesive slab, and remains loose, light, and dry. Some loose dry avalanches to size 1.5 were observed on Friday in the Elk Valley North, near Crown Mountain. Slope testing in the Crowsnest North on Thursday did not produce any shears or signs of instability. One old storm snow avalanche was reported size 1.5 that probably released during the storm. The deep persistent slab problem is a low probability/high consequence scenario that warrants extra caution around large open slopes, especially in shallow snowpack areas. There was a report on Tuesday of a size 3.5 avalanche at Mt Hosmer in the Lizard/Flathead region that released on or stepped down to the deep weak layer near the ground. On Wednesday we had a report from the Lizard range of another size 3.0 deep persistent avalanche on a northeast aspect in the alpine. Avalanche activity on Wednesday near Elkford was limited to loose snow up to size 1.5.

Snowpack Summary

In Elk Valley North on Friday, there was 3cm of new snow and 18 cm of light dry recent storm snow. The mid-pack in this location was well settled, but the bottom third of the snowpack was weak facets. Snow profile tests produced a moderate compression test that released in a sudden planar fashion down 75 cm on the facetted crystals. In the Crowsnest North on Thursday there was 15 cm of new snow, and 35 cm of recent storm snow above various old surfaces. The winds were reported to have been light from the west, and there was not a lot of evidence of wind transport. Near Elkford on Wednesday there was 20 cm of storm snow above a melt/freeze crust that developed from the rain last weekend. The height of snow was 170 cm and there was about 100-120 cm of settled snow above the weak layer of sugary facets that developed during the cold spell in December. Snow profile tests resulted in a hard shear in this location where the facets were sitting on a hard wind crust. Recent slope testing did not show any results. Some loose snow had released naturally from steep unsupported terrain.

Problems

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
A weak layer near the base of the snowpack has the potential for large avalanches, especially in areas with minimal rider compaction or thin variable snow cover.
Avoid lingering in runout zones.Avoid steep convexities or areas with a thin or variable snowpack.Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Storm Slabs

An icon showing Storm Slabs
Recent storm snow may be loose and unconsolidated in some areas. In areas where the storm snow has been transported by the wind, or settled into a slab, it may take a couple of days to bond to the old surfaces.
Pay attention to overhead hazards like cornices which could easily trigger deep slabs.Use ridges or ribs to avoid pockets of wind loaded snow.Be alert to conditions that change with elevation.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Feb 25th, 2017 2:00PM