Avalanche Forecast

Issued: Apr 6th, 2012 4:00PM

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

pmarshall, Avalanche Canada

South Coast.

Avalanche danger will rise during the day with intense spring sunshine and warming temperatures. Plan to be off big sun-exposed slopes early before the snow becomes moist or wet.

Summary

Confidence

Good

Weather Forecast

Synopsis: A ridge of high pressure should maintain mainly sunny skies on Saturday and Sunday. Freezing levels should climb to 1500m on Saturday and 1800-2000m on Sunday. Upper level winds are light and variable. An upper level low pressure system should spread more cloud and light precipitation on Monday. The freezing level should hover around 1600-1800m.

Avalanche Summary

Recent activity is limited to loose wet avalanches on steeper solar aspects during periods of sunshine. Previous 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

The snow surface consists of old wind slabs in exposed alpine terrain, spotty surface hoar on shady slopes, and a sun crust/moist snow on solar aspects. This sits on up to a metre of settling storm snow from last week. The March 27 layer, predominately crusty interface except north facing slopes at treeline and above where small surface hoar (5mm) may be found, is now down 60-120cm. 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

Loose Wet

Loose-wet avalanches are very likely in steeper south facing terrain during the afternoon. A heavy wet slide could have serious consequences if you are exposed to a terrain trap.

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

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 4

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

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 - 5

Valid until: Apr 7th, 2012 9:00AM