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Avalanche Forecast

Archived

Mar 1st, 2016–Mar 2nd, 2016

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

With several avalanche problems to deal with Wednesday, conservative terrain selection will be essential to stay safe because human triggered avalanches are still likely. Choose moderately angled terrain and avoid wind loaded slopes, saving those steeper lines for another day.

Detailed Forecast

Showers should wind down Wednesday morning with the next frontal system already moving in Wednesday afternoon. Despite a modest cooling trend, storm related danger will continue through Wednesday due to strong southwest winds loading lee slopes during moderate showers Tuesday night. 

Storm slab instabilities should be healing but may still be sensitive Wednesday. Wind slab will continue to build Tuesday night on lee slopes with moderate to strong west transport winds. Loose wet avalanches will become more likely on steeper slopes in the afternoon as snow levels begin to rise once again. Avalanches that begin in the new snow may become larger lower down the path as they entrain moist or wet snow.  

With several avalanche problems to deal with Wednesday, conservative terrain selection will be essential to stay safe because human triggered avalanches are still likely. Choose moderately angled terrain and avoid wind loaded slopes, saving those steeper lines for another day.

Snowpack Discussion

Weather and Snowpack

Springlike weather under high pressure  Feb 23rd and 24th led to abundant sunshine with temperatures climbing into the 40's. This weather allowed for melt-freeze crust formation and varying amounts of wet surface snow depending on slope aspect during the day. A weak front brought mostly light rain to Hurricane Friday night to Saturday morning.

A strong Pacific frontal system blew through the Olympics mid-morning Sunday. Around 12 inches of snow accumulated through Monday morning at Hurricane Ridge accompanied by a cooling trend. Moderate S-SW transport winds seen Sunday tapered off Sunday night. 

A warm front quickly changed snow to rain on early Tuesday morning with strong southerly winds. Rain changed back to snow at Hurricane Tuesday afternoon. 

The mid and lower snow pack along the west slopes should generally be a stable mix of crusts and layers of moist and rounded snow crystals.

Recent Observations

NWAC pro-observer Matt Schonwald was at Hurricane Ridge Friday and found mostly consolidated stable snow. N to E slopes had areas of 25-30 cm of wind transported 4F snow well bonded to 1F melt form grains in the upper snow pack. South through west slopes were melted out in some places with shallower dense stable snow in others.

No recent observations are available from the Olympics, but rainfall on Tuesday likely caused a natural avalanche cycle. 

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.

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.