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Avalanche Forecast

Archived

Feb 1st, 2013–Feb 2nd, 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 unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Northwest Coastal.

Confidence

Fair - Forecast snowfall amounts are uncertain on Sunday

Weather Forecast

Saturday: Overcast with no significant precipitation expected. Light amounts in the Northern part of the region. Alpine temperatures near zero degrees with freezing levels hovering around 1000-1300 m. Ridgetop winds will blow moderate from the South.Sunday: The brunt of the frontal system will take effect, bringing moderate precipitation accompanied by strong SW ridgetop winds. Alpine temperatures near -4.0 and freezing levels gradually falling to 800 m.  Monday: Cloudy skies with light precipitation. Ridgetop winds will blow light from the South. Alpine temperatures dropping to -7.0 with freezing levels lowering to 400 m.

Avalanche Summary

On Friday, several natural loose, slab and glide avalanches were spotted from a heli flight up to size 2.5. I suspect loose wet avalanches continued in below treeline elevations.

Snowpack Summary

Touchy wind slabs are most likely found on NE-W slopes and behind terrain features like ridges and ribs. Warmer temperatures have promoted settlement and consolidated the recent storm snow into slab-like characteristics. Lingering beneath (down 50-80 cm) sits a persistent weakness comprising of surface hoar, facets, and /or a crust. Recent test done on these layers are producing hard results with sudden and resistant planar results.  Keep these layers on your radar in regards to reactivity and sensitivity until we get through the warming period. Snow may become moist or wet at treeline and below and become unstable.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

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.