Avalanche Forecast

Issued: Jan 22nd, 2013 9:58AM

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

slemieux, Avalanche Canada

Purcells.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain on Wednesday

Weather Forecast

Tuesday night and Wednesday: The frontal system is pushing its way into the interior and precipitation should start later Wednesday. Between 5 to 10 mm is expected to fall during the day with moderate to strong winds from the SW in the alpine. Freezing levels will lower to valley bottom and the inversion will disappear. Thursday: A break before the next system. Expecting some clearing, winds tapering off staying from the W, temperatures also staying cool and freezing level to valley bottom.Friday: Expecting light precipitation and moderate SW winds.

Avalanche Summary

A few loose avalanches up to size 2 were reported on steep S-SE facing slopes.

Snowpack Summary

The new snow will fall on a variety of surfaces; windslabs in the alpine, facets, surface hoar below treeline in sheltered areas and a suncrust on South facing slopes. New windslabs and some sluffing in sheltered terrain is expected. These new layers will most likely be touchy for a certain time.The surface hoar layer below the 40-60 cm of generally well settled snow is still a concern to professionals, especially below 1900 m. in sheltered-shady areas and on S aspects. It still produces sudden planar shears in those areas as well as some resistant planars. A strong mid-pack overlies a weak facet/crust layer near the base of the snowpack, which is now considered inactive.

Problems

Wind Slabs

New windslabs will form where forecasted snow accumulates on lee side of the strong SW-W winds in alpine and at treeline.

Avoid areas where sluffing may have severe consequences.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

A cautious approach is recommended on steep S slopes and sheltered terrain below treeline.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Jan 23rd, 2013 2:00PM