Avalanche Forecast

Issued: Apr 4th, 2012 10:41AM

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

ccampbell, Avalanche Canada

South Coast.

Summary

Confidence

Good

Weather Forecast

Thursday: Unsettled conditions with scattered flurries and sunny breaks. Freezing levels around 1000m and light northerly winds. Friday and Saturday: A ridge of high pressure is expected to keep things mainly sunny and dry. Freezing levels are expected to hover around 800-1000m on Friday and slightly rise to 1200m for Saturday. Winds should remain light from the north.

Avalanche Summary

Observations from Tuesday are limited due to poor visibility. But heavy loading from snow wind and rain, as well as rapid warming, likely produced natural avalanches, and resulting storm and wind slabs, and cornices, are probably very touchy. Check out the telemarktips.com South Coast conditions forum for a report of a remotely triggered Size 3 slab avalanche on a north facing couloir in the east side of the Duffey Lake area on Sunday. The slab failed on basal facets and propagated 300m out of the couloir and wrapped around to the adjacent northwest.

Snowpack Summary

30cm of new snow in the Duffey Lake area in the past couple of days brings the total snowfall over the past week close to a metre, while rain followed by a skiff of new snow has resulted in dust-on-crust conditions in the Coquihalla area. The past week's snowfall overlies a predominately crusty interface, except north facing slopes at treeline and above where small surface hoar (5mm) may be found. Recent reports include hard but sudden compression tests results and a Rutschblock 4 whole block failure on this late-March surface hoar in the Duffey Lake area. Deep persistent weaknesses linger in many colder and shallower snowpack areas. The potential for remote triggering, step down avalanches, and wide propagations, makes the current snowpack structure particularly tricky to manage.

Problems

Wind Slabs

Thick fresh wind slabs are highly sensitive to human triggers and cornice falls,and sun-exposure is expected to make things even more touchy. Expect to encounter them below ridgecrests, behind terrain features, and in gullies.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Storm Slabs

Storm slabs could be easily triggered and have the potential to step-down to deeper weaknesses, especially with solar warming.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 5

Cornices

Large and weak cornices could easily start popping off with sun-exposure. Not only are they a hazard in themselves, but can also act as a heavy trigger for very large avalanches on the slope below.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 6

Valid until: Apr 5th, 2012 9:00AM