Avalanche Forecast

Issued: Jan 1st, 2012 9:28AM

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

ghelgeson, Avalanche Canada

Purcells.

Summary

Confidence

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

Weather Forecast

Warm air enters the region late Sunday persisting through mid-day Monday. Freezing levels are forecast to be between 1500 - 2000 m & winds in the alpine will be ripping out of SW @ 55 -95 k/hr A cold front moves in after lunch Monday lowering freezing levels and bringing light snowfall, 5 cm or so are expected Monday night. A weak ridge builds in Tuesday AM before a more organized low moves in Tuesday afternoon into Wednesday. We can expect 15 - 20 cm before the system exits to the east Wednesday afternoon.

Avalanche Summary

Explosive work in the region produced significant results to size 3.5. Saturday. A cycle reportedly occurred on Saturday with many paths running naturally to size 3 at treeline & above, failing on the mid-december surface hoar/facet/crust combo.

Snowpack Summary

100 - 140 cm of snow has fallen since Christmas bringing the total snowpack depth to around 200cm in the alpine. The holiday storm snow is now settling into a cohesive slab that sits above a very sensitive mid-December surface hoar layer. This layer continues to be sensitive to the weight of a skier or sledder. Testing on this layer reveals sudden planer results. Recent snowfall has also awoken the basil weakness near the ground on north facing slopes. This mixed bag of weaknesses has made for a very tricky avalanche situation as evidenced by the numerous accidents in the area over the last few days.

Problems

Wind Slabs

Winds continue to redistribute storm snow into fresh wind slabs. I'd be suspect of any open area, even below treeline. Once moving, a wind slab could easily step down and trigger a large avalanche.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

This layer continues to be touchy across the region. It's time to rein your terrain selection way in.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 6

Deep Persistent Slabs

The weight of the snowpack is pushing this layer over the tipping point in some locations. Avalanches triggered in more superficial layers have the potential to step down to this layer creating a deep and destructive avalanche.

Aspects: North, North East.

Elevations: Alpine.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Jan 2nd, 2012 8:00AM