Avalanche Forecast

Issued: Apr 5th, 2012 10:25AM

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

ccampbell, Avalanche Canada

South Coast.

Summary

Confidence

Good

Weather Forecast

Friday: Unsettled conditions with scattered flurries and sunny breaks. Freezing levels around 1000m and light winds. Saturday: A ridge of high pressure is expected to keep things mainly sunny and dry. Freezing levels are expected to hover around 1200m, and winds should remain light. Sunday: Some increasing clouds with light precipitation later in the day.

Avalanche Summary

Reports from the Duffey Lake area on Wednesday include evidence of numerous natural slab avalanches up to Size 2.5 from Tuesday morning on northerly facing alpine and treeline slopes. Most failed within the storm snow but late March surface hoar was the suspected culprit for some deeper releases. One notable cornice-triggered 1.4m deep Size 3 occurred on the North Face of Joffre. 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. Not only will daytime warming and sun-exposure cause surface snow to lose cohesion and cornices to weaken, they will also increase settlement rates and decrease slab stability.

Problems

Wind Slabs

Thick fresh wind slabs are highly sensitive to sun-exposure and cornice falls, and step-down potential could result in very large avalanches. Expect to encounter them below ridgecrests, behind terrain features, and in gullies.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

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 - 3

Persistent Slabs

The potential for remote triggering, step down avalanches, and wide propagations, makes the current snowpack structure particularly tricky to manage.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 6

Valid until: Apr 6th, 2012 9:00AM