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Avalanche Forecast

Archived

Mar 31st, 2015–Apr 1st, 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.

Don't be fooled on April 1st by the escalating avalanche danger with elevation. Watch for sensitive slab avalanches involving new snow on lee easterly slopes near and above treeline as well as loose wet avalanches on solar slopes during sunbreaks and daytime warming Wednesday.

Detailed Forecast

Additional light to moderate snow accumulations are expected Tuesday night through Wednesday at Mt. Hood. Moderate westerly transport winds are expected to continue through Wednesday. Showers may be locally intense Wednesday afternoon due to the unstable air mass over the region. 

Watch for sensitive slab avalanches involving new snow on lee easterly slopes near and above treeline as well as loose wet avalanches on solar slopes during sunbreaks and daytime warming Wednesday. Slabs may fail on graupel layers from Tuesday.

Cornices won't be listed as an avalanche problem but be aware of new cornice growth along ridgelines.

Snowpack problems west of the crest for the time being should be in the upper or surface layers. The mid and lower snowpack west of the crest consists of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter. Many areas at the lowest elevations do not have enough snow to cause an avalanche danger.

Snowpack Discussion

Winter made a bit of a comeback in the Northwest in mid to late March. Several storms or storm cycles brought heavy snow to the above treeline areas west of the crest especially on the volcanoes.

A vigorous front crossed the Northwest Friday night causing strong west-southwest winds along with some rain and snow. Snow levels lowered enough by Saturday to produce 2-3 inches of snowfall at higher NWAC stations west of the crest including at Mt Hood with likely a few more inches at higher elevations.

The Meadows patrol found some isolated shallow wind slab on Saturday on northeast slopes above 6500 feet. Mostly sunny and mild weather conditions were seen Sunday and Monday with no new avalanche problems reported. 

Snow levels fell quickly after a front moved through early Tuesday morning. Scattered snow showers through Tuesday afternoon had deposited several inches near and above treeline along with moderate westerly transport winds. In many areas the old moist surface should be slowly re-freezing with the new snow generally bonding well, keeping avalanche concerns confined to new storm snow layers.  

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.

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.

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.