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Avalanche Forecast

Archived

Feb 27th, 2014–Feb 28th, 2014

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

Regions

Northwest Inland.

Don’t let your guard down! The deeply buried weak layer may continue to be well preserved on shaded aspects. More info in the new blog post!

Confidence

Good

Weather Forecast

Overnight and Friday: The alpine inversion along the coast is expected to end overnight. We should see below freezing temperatures at all elevations during the day with Easterly winds in the alpine and strong Northeast outflow winds near the coast. Mostly clear with a chance of high thin cloud during the day.Saturday: Clear and cold with strong Northeast winds and alpine temperatures around -17. Very strong outflow winds near the coast.Sunday: Clear and cold with strong Easterly winds and alpine temperatures around -20.

Avalanche Summary

No new avalanche activity reported.

Snowpack Summary

Clear skies and cold temperatures combined with moderate Easterly or Northeasterly winds have developed new wind slabs in the alpine and at treeline. 35-90 cm of settled storm snow overlies a variety of old surfaces including weak facets, surface hoar (more predominant at tree line and below tree line elevations), a scoured crust, wind pressed snow, or any combination of these. Whumpfing, cracking, and reports from the field indicate a very poor bond between the new snow and these old surfaces. Recent snowpack tests give easy or moderate "pops or drops" shears on this persistent weakness and show potential for wide propagation. A lack of activity on this layer is likely because the overlying snow has not settled into a slab due to the recent cold temperatures.

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.