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Avalanche Forecast

Archived

Dec 22nd, 2012–Dec 23rd, 2012

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

Regions

Glacier.

You may have noticed that the "persistent deep slab" is not a "problem" right now. While these layers still exist, the likelihood of triggering is low. Professionals are still tracking these layers, which may become a concern when conditions change.

Weather Forecast

Over the weekend we should see mostly overcast skies, light flurries (up to 5 cm today) and moderate southerly winds. Expect to see some transport of the new snow at ridgetop. A brief ridge of high pressure will bring back the sun on Monday and for Christmas day!

Snowpack Summary

SW winds overnight on Thursday formed thin windslabs on lee features above treeline. Recent storm snow has settled to ~40cm sitting on well settled snow. The Nov28 surface hoar is down about 80cm where it exists, and the early Nov crust is widespread and down about 1.5m. Tests on these layers indicate they would be hard to trigger.

Avalanche Summary

10-20 cm thick windslabs are reactive to human triggering on convex rolls and unsupported terrain at treeline and above. These avalanches were reported to be size 1's: 20-30m wide and 30m long. Overnight on Thursday, numerous size 2-3 natural slab avalanches were triggered by wind loading on steep N thru E aspects.

Confidence

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.