Avalanche Forecast

Issued: Feb 18th, 2013 9:51AM

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

triley, Avalanche Canada

Purcells.

Summary

Confidence

Fair - Due to variable snowpack conditions for the entire period

Weather Forecast

Overnight and Tuesday: A weak upper trough is forecast to move across the region tonight bringing moderate Southwest winds. The trough should continue to influence the interior regions on Tuesday. Expect mostly cloudy conditions with light winds and very light precipitation. Freezing levels are expected to rise to about 1000 metres during the day.Wednesday: The next weak ridge of high pressure should move into the interior ranges to fill in behind the trough as it exits into Alberta. Expect gradually clearing skies, light winds and freezing levels near the valley bottoms. There is a chance of some strong solar radiation in the afternoon.Thursday: Another trough is expected to drift into the interior from the coast. Snow fall amounts are un-certain at this time.

Avalanche Summary

There was one report of a skier controlled avalanche size 1.0 on an East aspect in the alpine on Sunday that was about 20 cms deep.

Snowpack Summary

The latest storm did not make it into most of the region. The February 12th weak layer of surface hoar is buried down anywhere from 15 cms in the Northeast of the region to 60 cms in the Southwest of the region. The January 23rd layer is buried down about 100 cms and continues to be a concern for professionals. Cornices are reported to be large and weak, and may fall off naturally.

Problems

Storm Slabs

The buried February 12th surface hoar layer is expected to continue to be reactive. The amount of snow above the weak layer is variable across the region.

The new snow will require several days to settle and stabilize.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Wind Slabs

New wind slabs have developed at higher elevations in areas that received new snow and wind.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Travel on ridgetops to avoid wind slabs on slopes below.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Persistent Slabs

There are a couple of older layers of buried surface hoar and crust combinations that are buried down about 70 cms and 100 cms, that may be triggered by large additional loads.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Feb 19th, 2013 2:00PM