Avalanche Forecast

Archived

Feb 8th, 2015–Feb 9th, 2015

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.

Regions

Mt Hood.

A heightened avalanche danger will mainly be limited to steep open terrain or lee slopes above treeline.

Detailed Forecast

Warming is expected Monday with periods of light to moderate rain and snow with generally light to moderate winds. Rain near and below treeline should maintain some wet surface snow conditions, making triggered small loose wet avalanches possible on steeper slopes.

At the highest elevations, generally above 6000 feet, some building storm or wind slab is expected. These areas of storm or wind slab may build on isolated terrain features, such as lee aspects near ridges, mainly NW through NE facing.

Do note as a result of the unseasonably low snowpack, especially at lower elevations, numerous terrain hazards such as open creeks, partially covered rocks and vegetation are widespread.

Snowpack Discussion

A combination of very mild weather with sunny days or minor rain or snow in late January caused further melt, consolidation and the formation of a thick, strong and stable crust.

The Mt Hood area had less impact from the bulk of the wet weather the PNW has experienced over the past three days, receiving a little shy of 1.5 inches of water. Some cooling with the storm Saturday caused small accumulations above about 6000-6500 feet with up to about 2-4 inches of wet snow.

No avalanches were seen or reported by the Mt Hood Meadows pro-patrol through Sunday afternoon with recent wet snow well bonded and not causing any significant loose wet problems near and below treeline.

The mid and lower snowpack at Mt Hood should consist of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.