Avalanche Forecast

Issued: Feb 1st, 2013 9:32AM

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

triley, Avalanche Canada

Purcells.

The weather forecast says that you better put your sun screen on for Saturday! The snow pack doesn’t have sun screen, so it might start peeling off if the sun gets too hot or alpine temperatures get too warm.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Saturday

Weather Forecast

Overnight and Saturday: Light Northwest winds and thin high cloud overnight with freezing down to the valleys. Light West winds with mostly clear skies with a chance of valley cloud and the freezing level rising up to about 1900 metres. A chance of an above freezing layer in the alpine during the afternoon; chance increases as you move to the South.Sunday: Freezing levels dropping to about 1400 metres and alpine temperatures moving down to about -3.0 as the cloud cover thickens in advance of the next pulse of moisture coming from the coast.Monday: West winds building during the day with light flurries becoming moderate snow by evening.

Avalanche Summary

Natural avalanches size 1.0 have been reported from steep un-supported terrain features.

Snowpack Summary

Westerly winds and warm temperatures overnight have continued to develop wind slabs in the alpine and at treeline. Wind slab was reported to be stiffening from fist to four finger hardness. The recent storm slab has been settling and becoming more cohesive. Pockets of slab that were mostly between 30-50 cms deep above the January 23rd weak layer have started to release naturally or when light additional loads have been added (like ski-cutting). As we head into a warming period expect the recent storm slab to become more reactive. The forecast warm temperatures at higher elevations on Saturday may help initiate releases on the January 23rd layer. The deeper weak layer from January 4th is reported to be gaining strength, and I don't expect that we will see releases on this layer from one day of solar radiation and warm temperatures. That being said, if cornices start to fall off from the heating on Saturday, that might be enough of a load to trigger the deeper January 4th layer.

Problems

Wind Slabs

Recent wind slabs continue to be triggered by light additional loads. Wind slabs may become more reactive during periods of strong solar radiation, or if alpine temperatures reach above freezing values.

Be cautious as you transition into wind affected terrain.>Stay well to the windward side of corniced ridges.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

The recent storm snow continues to settle into a cohesive slab above weak layers and variable old surfaces. This slab may become more reactive during the forecast warm temperatures and solar radiation.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Watch for wet loose or slab activity with forecast warm temperatures.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Cornices

Cornices may not be well anchored. Forecast warm temperatures may cause them to fall off naturally.

Avoid steep slopes below cornices.>Extra caution needed around cornices with current conditions.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 5

Valid until: Feb 2nd, 2013 2:00PM