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Avalanche Forecast

Archived

Mar 8th, 2014–Mar 9th, 2014

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

Regions

Northwest Coastal.

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Tonight and Sunday: Periods of snow 20-30 cm. The freezing level is around 600-800 m. Winds are strong easing to moderate from the W-SW. Monday: Cloudy with sunny breaks and possible flurries. The freezing level is around 800 m. Winds are light but gusty from the W-SW. Tuesday: Periods of snow, heavy at times. The freezing level is around 1200-1500 m and winds increase to strong from the SW.

Avalanche Summary

Numerous size 1-2 rider triggered slab avalanches were reported throughout the region on Friday. It's likely a fairly widespread natural avalanche cycle occurred in many areas later on Friday afternoon when the storm peaked. Expect natural avalanche activity to taper off over the next couple days, while the potential for rider triggering remains high.

Snowpack Summary

40-70 cm of storm snow now sits on a layer of surface hoar or sugary faceted snow on shady slopes, a sun crust on steep solar aspects, or hard wind slabs and scoured slopes in exposed terrain. Initial tests on this new interface showed a poor bond between the new snow and old snow surface. Weaknesses may also exist within the new storm snow. The mid February weak layer of surface hoar or a crust/facet combo is buried 60-120 cm deep. There has been no reported activity on this layer recently, but the recent heavy snowfall and rapid warming could have triggered some large avalanches. Basal facets and/or depth hoar remain a concern in shallow snowpack areas in the northern part of the region.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.