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Avalanche Forecast

Archived

Jan 30th, 2013–Jan 31st, 2013

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

Regions

Northwest Coastal.

Confidence

Fair - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

Thursday: Storm snow 10-25 cm with heaviest amounts West of Terrace. Ridgetop winds blowing 30-60 km/hr from the West. Alpine temperatures near -4 and freezing levels rising to 600 m.Friday: Continued cloudy skies and snow amounts near 5 cm. Ridgetop winds light from the SW. Alpine temperatures near -2 with freezing levels rising to 900 m.Saturday: Moderate-heavy precipitation. Ridgetop winds light from the South. Alpine temperatures -3.0 with freezing levels near 800 m.

Avalanche Summary

Two slab avalanches size 2.5 naturals occurred out of steep wind loaded terrain on an East aspects. Numerous size 2.0 loose and moist avalanches occurred naturally on steeper solar aspects in the afternoon.

Snowpack Summary

The region has received close to a meter of recent storm snow. This new snow has been building storm and wind slabs over a variety of old snow surfaces (old wind slabs, melt-freeze crusts, surface hoar and scoured slopes). Much of the recent snow is being drifted into big wind slabs by strong NW wind.  Reports generally indicate that the bulk of this storm snow seems to be settling quickly, which is a good. However, with a continued stormy pattern I would wait out the storms and watch how the snowpack adapts.Lingering beneath the new snow sits two persistent weaknesses comprising of surface hoar/ facets and a melt-freeze crust. I suggest you keep these on your radar in regards to reactivity and sensitivity with the additional loading pattern. If reactive, with up to a meter of new snow regionally,  these buried weaknesses may be susceptible to producing large avalanches. The mid and lower snowpack is generally well settled and strong, although basal facets remain a concern 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.