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Avalanche Forecast

Archived

Dec 24th, 2019–Dec 25th, 2019

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

Glacier.

While natural activity has tapered off, human triggered avalanches are still quite possible. Make conservative terrains choice. This is not the time to go all out.

Weather Forecast

Cloudy with sunny periods and isolated convective flurries bringing trace amounts of precipitation.  The alpine temperature will reach a  high -8 °C with the freezing level rising to 900m. Winds will be mostly light from the SW. Valley cloud is likely at lower elevations where a slight temperature inversion exist.

Snowpack Summary

The top 70cm of snow remains fairly unconsolidated in most places, and still has that post-storm powdery feeling. A new surface crust exists on steep solar aspects. The Dec 11th SH (5-12mm) is well preserved and is now down 90-120cm. The Nov 23 SH/Cr is down 160-185cm. Early season crusts still persist in the lower snowpack.

Avalanche Summary

Helicopter deployed explosives produced a large size 3.0 slab avalanche on Mt Fidelity, in an area that was previously uncontrolled. The natural avalanche cycle has tapered off, however human triggered avalanches in areas that haven't slid remain likely.

Confidence

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.

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.