Avalanche Forecast

Archived

Dec 23rd, 2012–Dec 24th, 2012

Alpine

Natural avalanches possible, human triggered probable.

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

Northwest Inland.

We have limited observations from the region. Send us yours! [email protected]

Confidence

Poor - Due to limited field observations

Weather Forecast

Monday: Light S winds, with moderate to strong NE outflow winds in places. Alpine temperatures around -14 with an inversion (colder temperatures in the valley floor). No precipitation.Tuesday: Light winds. Alpine temperature around -10 with an inversion. No precipitation.Wednesday: Light SE winds. Alpine temperature around -10. No precipitation.

Avalanche Summary

No recent avalanches have been reported.

Snowpack Summary

Wind slabs and cornices are likely to have developed on a fairly widespread basis and may be found in unusual locations lee to NE and E outflow winds. Spotty surface hoar was buried in the upper snowpack in sheltered treeline areas, although little is known about its reactivity. Near the base of the snowpack, a facet/crust layer remains a concern for unlikely but possible deep releases. It may be possible to trigger this weakness with a very heavy load (e.g. cornice fall) or from a thin-spot trigger point.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.