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Avalanche Forecast

Archived

Apr 11th, 2015–Apr 12th, 2015

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

Mt Hood.

Human triggered slides are likely on wind loaded aspects above tree-line. Increasing sun or filtered sun may quickly destabilize recent snow on sun exposed slopes. Choose more moderate and less wind affected terrain and safely enjoy a taste of winter. 

Detailed Forecast

 

Showers should continue overnight Saturday, then end early Sunday with partial clearing expected. Freezing levels should remain low with moderate westerly ridgetop winds. This should continue to build areas of wind slab on lee slopes in the upper elevations as well as build cornices along ridges.  

Even with the winter-like temperatures, mid-April sunbreaks in the late morning or mid-day can trigger loose wet avalanches involving the new storm snow on solar aspects.  

Cornices won't be highlighted as an avalanche problem due to the cool weather, but use caution on slopes below cornices and on ridges where it can be hard to know if a large cornice is present.

Snowpack Discussion

A winter-Iike frontal passage Friday night was followed by cool showers in moderate to strong westerly winds Saturday. This has deposited from about 4-8 inches of new snow as of Saturday afternoon at Mt Hood. Reports from patrol at Mt Hood Meadows Saturday, indicated that shallow wind slabs were forming on many lee east facing slopes near treeline, but no triggered slides were noted. No reports were available from higher terrain due to very strong winds and white out conditions.The new snow was reportedly fairly well bonded to the old snow surface.

Snowpack problems at Mt Hood should remain in the most recent upper or surface layers. The mid and lower snowpack at Mt Hood consists of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this season. Many areas at low elevations do not have enough snow to cause an avalanche danger.

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.