Avalanche Forecast

Archived

Dec 11th, 2019–Dec 12th, 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 possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Mt Hood.

New snow and wind will create dangerous avalanche conditions on Thursday. Strong winds will quickly load lee slopes and build fresh wind slabs at upper elevations. The new snow is most welcome but early season conditions exist; be aware that a small avalanche can cause injury if you take a ride through shallowly buried rocks, stumps or other ground hazards.

Discussion

It was pretty bony out there prior to Wednesday night’s storm with variable and generally low snow coverage summing up the early season snowpack. No recent avalanches have been reported, nor do we have a critical snowpack structure to describe, we are waiting for snow to pile up just like everyone else.

With all the excitement for winter’s return, it’s imperative to think about what’s lurking just below the surface in many places - ground hazards that will amplify the consequences of any size avalanche, even a small one.

Snowpack Discussion

Regional Synopsis Coming Thursday, December 12, 2019

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.

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.