Avalanche Forecast

Issued: Jan 28th, 2013 8:41AM

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

Avalanche Canada istorm, Avalanche Canada

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

The pattern through Tuesday is a fast NW flow before shifting back to a more typical westerly flow on Wednesday & Thursday.Overnight Monday & Tuesday: Mod to strong NW  or W wind with below freezing temps above approximately 800m. Less than 10mm water equivalent precipitation (falling as about 10 cm of snow up high).Wednesday: Winds easing to light (possibly moderate in some places) from the NW, drying out so no precipitation other than flurries expected. Temperatures slightly warmer and the possiblity of an inversion (warmer & sunnier up in the alpine; colder and depressing under the valley cloud).Thursday: SW wind with about 15 mm of water equivelant (rain low, snow high) and slightly warmer than Wednesday (freezing level rising to 1500 m possible).

Avalanche Summary

Sunday's reports from professional avalanche safety operations almos unanomously reported "No New Avalanches".

Snowpack Summary

Accumulations around 30cm of snow over the past 7 days overlies a variety of old surfaces including hard wind slabs, thin and thick crusts and large surface hoar crystals (found in sheltered areas below treeline). Recent winds from the SW have shifted snow into soft and hard slabs anywhere from 25-40 cm thick on lee slopes. Watch for the next round of wind coming in from the NW resulting in reverse and cross-loading many slopes.Deeper in the pack, not much is new or going on. The early January surface hoar layer is buried down 40-80 cm and seems to be gaining strength. Reports indicate that this layer is mainly unreactive, and would require a large trigger to set it off. Near the base of the snowpack, a crust/facet layer exists, which is now unlikely to be triggered, except perhaps by heavy triggers in unsupported, shallow, rocky terrain where more faceting has taken place.

Problems

Wind Slabs

An icon showing Wind Slabs
Watch for a shifting wind to the NW as it increases in strength - forming windslabs in "reverse loaded" and cross-loaded terrain behind ridges and ribs. Watch for the effect of warm temperatures & solar radiation on Wednesday & Thursday.
Assess start zones carefully and use safe travel techniques.>Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Valid until: Jan 29th, 2013 2:00PM