Avalanche Forecast

Issued: Mar 29th, 2016 9:20AM

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

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

Weather Forecast

A well-embedded ridge of high pressure will keep the region warm and sunny for the forecast period. Ridgetop winds will be generally light, while freezing levels will sit at about 2200m on Wednesday and then climb to about 2700m for Thursday and Friday.

Avalanche Summary

On Monday, storm slabs (mostly in the size 1.5 range) were reported in high elevation, wind exposed terrain. The sun will become the main driver for avalanche activity throughout the forecast period. Although warming will promote settlement and strengthening within the recent storm snow, loose wet avalanches and cornice falls will become the most common avalanche type. My main concern, however, remains isolated yet destructive releases on deeper weak layers which formed earlier in the season. 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

13-25cm of new snow from Sunday night overlies small surface hoar on shaded slopes at treeline and in the alpine. Snow surfaces are now well into a daily melt-freeze cycle on all aspects below treeline and sun-exposed slopes at higher elevations. Cornices are large and looming and will become increasingly weak with forecast warming and solar radiation. About 25-50cm below the surface, you'll likely find another hard crust which exists everywhere except high, north-facing terrain. The late February persistent weak layer down 70 to 120 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.

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

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Loose Wet

Watch for pushy loose wet avalanches at all elevations throughout the forecast period. The combination of buried crusts and solar radiation will make conditions extra touchy on sun-exposed slopes.

Avoid exposure to solar aspects overhead, large avalanches may reach the end of run out zones.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

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

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

Intense spring sun and rising temperatures could reactivate buried persistent weaknesses in the mid and upper snowpack. Avalanches at these interfaces would be surprisingly large and destructive.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Minimize exposure to overhead avalanche terrain, large avalanches may reach run out zones.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Mar 30th, 2016 2:00PM