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Avalanche Forecast

Archived

Dec 23rd, 2021–Dec 24th, 2021

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

Regions

Glacier.

Soft slabs and fast, loose avalanches will be easy to trigger under the weight of a person for the next couple of days. Be aware this additional load could be enough to trigger a deeper slab on the Dec 1 crust.

Weather Forecast

Cold air from the north smacks into moist, warmer air from the SW for the next couple of days, bringing light/mod snowfall to the region.

Tonight: Flurries, Alp low -14*C, light SW winds

Fri: Flurries, 5cm, Alp high -11*C, light SW winds

Sat: Flurries, 10cm, Alp high -11*C, light/gusting strong S winds

Sun: Flurries, trace, Alp high -22*C, light E wind

Snowpack Summary

40+cm of snow and moderate S'ly winds have formed a storm slab on top of cold, faceted surfaces. The December 1st crust is buried approximately 80cm-150cm, with weaker sugary snow directly above and below. Beneath the Dec 1st crust-facet combo, the snowpack is dense and strong.

Avalanche Summary

Strong gusty winds, new snow, and warming temperatures triggered a natural avalanche cycle Thurs morning to sz 3.5. Artillery control has produced numerous sz 3-3.5 avalanches to valley bottom. Human triggered avalanches are likely in steep, unsupported terrain.

Confidence

Forecast snowfall amounts are uncertain

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

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.