Summary Avalanche Forecast for Olympics and Washington Cascades

   Northwest Weather and Avalanche Center Seattle Washington

   1403 PM PDT Mon May 14 2012

   This forecast applies to back country avalanche terrain below 7000 feet
   and does not apply to developed ski areas or highways.

   Please note that regular forecasts for this season have ended. Special
   forecasts will be issued this spring only if unusually severe avalanche
   conditions develop.

   This special forecast applies to Monday and Tuesday 14 and 15 May and
   will be updated as conditions warrant.

Avalanche Forecast

                        Olympics, Washington Cascades

   Monday and Tuesday: Further sunny hot weather Monday and Tuesday with
   light winds should allow for continued warming, melt and weakening to
   possible affect progressively deeper layers of the snowpack at
   increasingly higher elevations.

Snowpack Synopsis

   Recent Weather, Snowpack and Avalanche Activity: Last week a cool but
   mainly dry upper trough brought substantially lowered freezing levels.
   This temporarily reduced avalanche activity due to a combination of
   decreased melt and increasing surface crust formation.

   An upper ridge over the US west coast, a warm air mass, offshore
   surface flow and much warmer temperatures developed over the recent
   weekend. Back country skiers reported mainly spring conditions,
   increasing surface wet snow conditions in some areas, with some
   potential wet snow instability and some shallow wet snow avalanches.

Monday and Tuesday

   The strong upper ridge should move east over the Northwest Monday and
   Tuesday with freezing levels reaching 13-14,000 feet in the Olympics
   and Cascades along with strong sunshine and light winds. This most
   significant and prolonged warming so far this year should produce
   further surface snow melt with resulting meltwater percolating into and
   progressively weakening and lubricating increasingly deep snow
   layers...probably reaching the ground in some locations. As a result, a
   significant spring slide cycle involving large wet loose slide
   releases, substantial cornice fall and glide crack activity, and
   possible large wet slab slides is expected Monday and Tuesday.

   Abundant natural wet loose or possible wet slab avalanches should be
   likely Monday and Tuesday, especially from late morning through the
   afternoon hours each day. Cornice failures should remain likely as
   well...and some wet slides should become large and potentially
   destructive, involving mud, rocks and trees and likely running to the
   valley floors.

   Concern #1: Increasingly large and dangerous wet loose or wet slab
   avalanches.

   Concern #2: Increasing likelihood of cornice failures, which may
   entrain large amounts of wet snow on the slopes below and trigger both
   large wet loose and wet slabs avalanches.

   Concern #3: Glide cracks where full snow pack releases to smooth
   underlying surface such as rock faces are probable.

   Travel on relatively flat terrain at lower elevations may be dangerous
   if connected to higher elevation slopes as slides beginning at higher
   elevations could easily become very large and quickly reach lower
   elevation areas.

   As a result of this hopefully final spring avalanche cycle, careful
   snowpack evaluation and caution is recommended through Tuesday. In
   order to ensure their safety during this period of increased frequency
   and severity of spring avalanches, back country travelers will need to:
     * be very observant of changing snowpack conditions
     * manage terrain choices very wisely
     * be very conservative in decision making


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   NWAC weather data and forecasts are also available by calling
   206-526-6677 for Washington, 503-808-2400 for the Mt Hood area, or by
   visiting our Web site at www.nwac.us.
   Ferber/Northwest Weather and Avalanche Center Seattle Washington

References