Avalanche Forecast

Issued: Mar 30th, 2016 9:53AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Cornices, Persistent Slabs and Loose Wet.

jlammers, Avalanche Canada

Kootenay Boundary.

Solar warming will drive the Avalanche Danger throughout the forecast period. Watch your overhead hazard as large and destructive avalanches may reach their run-out zones.

Summary

Confidence

High - The weather pattern is stable

Weather Forecast

A well-embedded ridge of high pressure will keep the region warm and sunny for Thursday and Friday, while increased cloud is forecast for Saturday. Freezing levels should hover around 2800m for each day of the forecast period. Ridgetop winds will remain generally light.

Avalanche Summary

A few small wet slabs were observed around Kootenay Pass on Tuesday. They undoubtedly occurred in response to warming and solar radiation. At the time of publishing no other avalanches were reported, although this may reflect a lack of observations rather than actual conditions. The sun has become the main driver for avalanche activity. Although warming has promoted settlement and strengthening within storm snow from last weekend, loose wet avalanches and cornice falls have become the most common avalanche type. A major concern, however, remains isolated yet destructive releases on deeper weak layers which formed earlier in the season (see snowpack description). Avalanches on these layers could run surprisingly long distances, and may be triggered by a cornice fall, a surface avalanche in motion or extended periods of warming.

Snowpack Summary

On shaded slopes above 1900m you'll still find cold winter snow which is reported to be settled and faceted on sheltered slopes, and wind-affected in exposed areas. Warm temperatures have promoted a daily melt-freeze cycle on all other snow surfaces. Cornices are large and looming and have become increasingly weak with the sunny weather. In the upper snowpack you'll likely find a few hard crusts which exist everywhere except on high, north-facing terrain. The late February surface hoar/ crust interface (down 80 to 130 cm) remains a low probability/ high consequence concern. Test results are variable, with occasional sudden planar (pop) results. While generally becoming unlikely to trigger, this layer could produce surprisingly large and destructive avalanches with a cornice fall or warm temperatures.

Problems

Cornices

Large fragile cornices threaten many slopes and will become increasingly touchy with solar radiation. A cornice fall could be the large trigger required to awaken destructive buried weak layers.

Do not travel on slopes that are exposed to cornices overhead.>Give cornices a wide berth when travelling on or below ridges.>Cornices become weak with daytime heating, so travel early on exposed slopes.>

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Persistent Slabs

Intense spring sun and rising temperatures could reactivate buried persistent weaknesses in the mid and upper snowpack. Avalanches at these interfaces could be surprisingly large, so watch your overhead hazard and avoid slopes threatened by cornices.

Minimize exposure to overhead avalanche terrain, large avalanches may reach run out zones.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Loose Wet

Warming will promote pushy loose wet avalanches at all elevations throughout the forecast period. Multiple crust layers exist on solar aspects making destructive wet slab avalanches a concern as well.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Mar 31st, 2016 2:00PM