Avalanche Forecast

Issued: Mar 20th, 2016 8:57AM

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

bcorrigan, Avalanche Canada

Kootenay Boundary.

Be wary of steep south facing slopes, cornices and rising temperatures. Conservative terrain choices should be in your trip planning.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

A pacific cold front is moving into the region bringing cloudy skies and light amounts of precipitation. MONDAY: Cloudy with the freezing level hovering around 1500 m, light south to southwest winds, scattered light rain showers below 2500 m. TUESDAY: Cloudy with flurries and/or light rain, freezing level dropping to 1200 m, winds will be light, south to south west. WEDNESDAY: Light precipitation in the late afternoon, winds forecast to be light from the south, freezing level dipping overnight to 1000 m, then climbing to 1600 m during the day.

Avalanche Summary

Reports of human triggered avalanches have dropped off in the past few days, but there are several reports from yesterday of natural cornice failures producing large (size 2.5 to 3 ) avalanches. These cornice failures triggered the deep persistent weak layer mentioned in the snow pack discussion, buried on Feb 27th. Light to moderate south winds accompanying the incoming precipitation may build wind slabs on lee ( N-NW ) features in the coming days.

Snowpack Summary

Warm temperatures and strong solar radiation have aided settlement and encouraged bonding of the last blast of storm snow. Be aware that there are still multiple buried crusts at treeline and below. Of note are the March 11th crust, and a second crust, (the early March melt/freeze crust) can be found down 50 to 80 cm. The late February (Feb 27th) persistent weak layer of buried surface hoar, is now down 70 to 120 cm. This layer has been the interface for some large avalanches and is worth keeping in mind ( and perhaps looking for by digging a test pit) We suspect that this weak layer is more prominent on northerly (shaded) aspects at and above 1700 m. It may also be found associated with a crust on solar aspects. As the sky clouds over and the freezing level lowers, it's still worth paying attention to moist or wet surface snow . The potential is there for deep weak layers to become reactive. Cornices and exposure to cornice run-outs are definitely still something to be concerned about.

Problems

Storm Slabs

The storm slab should be bonding now, but may still be triggered in select locations.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Avoid freshly wind loaded features.>Choose well supported conservative lines and watch for clues that indicate instability.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 4

Persistent Slabs

This weak layer has shown recently that large triggers ( cornice failure ) can make it reactive.

Surface avalanches in motion could step down and initiate persistent slab avalanches which have the potential to be large and destructive.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar. >

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 5

Loose Wet

Still possible on steep south facing slopes as the day warms up.

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: North, North East, East, South East.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Mar 21st, 2016 2:00PM