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Avalanche Forecast

Archived

Feb 25th, 2012–Feb 26th, 2012

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

South Coast.

Confidence

Good

Weather Forecast

Sunday: Expect unsettled conditions, with occasional flurries, gusty northerly winds and temperatures reaching -2. Monday & Tuesday: Predominantly dry with a mix of sun and cloud. Winds turn from northerly to southerly with temps should reach -4 each afternoon.

Avalanche Summary

We have reports of isolated natural avalanches up to size 2.5 from both the Duffey lakes and the Coquihalla areas predominantly on north aspects at or slightly above treeline. Numerous ridder triggered avalanches up to 1.5 have also been seen in the recent storm layers (top 30cm).

Snowpack Summary

In the west side of the Duffey lake region up to 20cm of new snow fell in the last 24 hours, while on the east side the values are roughly half that. The Coquihalla area received roughly 30cm. This brings the recent storm values up to 40/30/60 respectively. The southerly winds have lee loaded open treeline and alpine terrain that faces north through east. Compounding the wind slabbing, the increasing temperatures have settled much of the storm snow into a cohesive storm slab, especially at treeline and below. The new snow sits on a variety of surfaces including crusts at lower elevations, surface hoar in protected areas and hard windslabs in the alpine. Below this the lower snowpack is well bonded and strong.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.