Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Seattle Washington
330 PM PST Sat Feb 13 2016
Synopsis...rain continues across western Washington tonight as a
warm front moves inland. Moist westerly flow aloft will continue
Sunday through early next week. The air mass will remain mild and
rain may be heavy at times in the mountains. An upper level trough
will bring showers and cooler weather on Wednesday.
Short term...rain will continue across western Washington tonight
as a warm front moves inland. Rain will be heavy at times along the
coast with up to 1.50 inches expected. The Olympics will see 1-3
inches and a Flood Watch remains in effect for the Skokomish River
in Mason County. The Skokomish River is already running high from
precipitation on Friday. Rain amounts will range from 0.25-0.50 in the
interior...with higher amounts possible in the southwest interior.
Winds aloft will turn westerly behind the warm front this evening
with heavy precipitation focused along the Cascades. Snow levels are around
4000-5000 feet with heavy snow possible at Paradise and Mount Baker -
a Winter Weather Advisory remains in effect.
Strong moist westerly flow will continue tomorrow through early next
week. The air mass will remain mild with temperatures mainly in the
50s. Models show a plume of moisture aimed at western Washington and
southern b.C. With possible heavy precipitation in the mountains...snow
levels are around 6000 feet. The precipitation bullseyes are wavering
north/south in the models but may see several inches of rain in the
Cascades...especially the central and northern Cascades. A few
rivers are close to flood stage and a hydrologic outlook has been
issued. The Lowlands will be wet and breezy through the period as
well. But with westerly downslope winds off the Olympics the Seattle
area may see a few breaks in the rain. 33
Long term...an upper level trough digging offshore may finally
break the moisture tap over western Washington on Wednesday. This would
bring an end to the steady heavy precipitation in the mountains. But the
trough will then shift inland Wednesday night for additional showers
and cooler conditions. Thursday remains cool and showery with the
trough overhead. Then another wet Pacific frontal system will arrive
on Friday. So the weather is still pretty active through the end of
next week. The models do show a weak upper level ridge next weekend
which may gives US a break in the action. 33
Hydrology...there is potential for heavy rain over the Olympics
tonight which may push the Skokomish River in Mason County over
flood stage. A Flood Watch remains in effect.
A warm front will stall over southern British Columbia or western Washington
Sunday through Monday...possibly into Tuesday. Heavy rain is
forecast in the north and central Cascades and a few rivers will be
close to flood stage. A hydrologic outlook has been issued. 33
Aviation...strong west flow aloft on the northern periphery of an
upper ridge will push a warm front across western Washington this evening. This
will result in a deeply moist and stable air mass for the next 24
hours with periods of rain leading to some reduced visibility.
Lots of MVFR ceilings late this afternoon...dropping into IFR range below 020
this evening as moistening onshore component of surface wind picks up
behind the front.
Ksea...looking for a break in the rain to begin around 03z...but ceilings
will continue to slowly come down as a warm front brings moister low-
level air into Puget Sound sound this evening. Break in the rain may last
until about 09z...then rain will start again and be heavy enough to
reduce visibility until about 14z. For most of Sunday...richly moist low-level
air mass will lead to IFR ceilings below 020 nearly all day...but a turn
to west-northwest flow aloft should limit rain at the terminal...or at least
keep it light...due to rain shadowing off the Olympic Mountains haner
Marine...recently hoisted a Gale Warning for the coast based on a
gale-force ob from Destruction Island. Will be monitoring the East
Entrance of the Strait closely as its winds peak over the next 2-3
hours. All the wind is being caused by an incoming warm front. Winds
will ease in most places after the front passes east during the
evening. Looks like a relative lull in wind early Sunday morning. On
Sunday afternoon...an east-west oriented front will develop over the
waters...most likely along a line from Kalaloch to Everett. SW winds
will pick up south of the front and peak on Sunday evening...with some
westerlies down the Strait. Atmospheric pressure will fall to our
north on Monday...initiating stronger south gradients throughout the
Washington...Winter Weather Advisory until 10 am PST Sunday for Cascades of
Pierce and Lewis counties.
Winter Weather Advisory until 4 am PST Sunday for Cascades of
Whatcom and Skagit counties.
Flood Watch Mason County.
Pz...Gale Warning coast.
Small Craft Advisory all other waters.
Small Craft Advisory for rough Grays Harbor.
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