Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 240410
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
900 PM PDT Tue May 23 2017

.SYNOPSIS...A cold front will sweep through Western Washington this
evening, bringing windy conditions to areas near the Strait and
Admiralty Inlet. A much cooler air mass will result on Wednesday
and Thursday. An upper ridge will bring warmer and drier weather
over the weekend.

&&

.SHORT TERM...The KUIL-KBLI gradient has been holding between +6.0
and +7.5 since 2 PM. Strong winds down the strait have affected the
Admiralty Inlet area. High wind was recorded at KNUW, with sustained
41 mph and a peak of 59 mph. There have also been windy conditions
in the Eastern Strait zone and on San Juan Island. Winds have not
been particularly strong in the Everett area--a few gusts in the low
30s seems to be the highest--but there have been isolated power
outages around the north shore of Lake Washington and as far east as
Duvall. These appear to be caused mostly by falling trees, and more
trees appear to be falling than is usual for these wind speeds
because of the unusual northerly wind direction. The high wind
warning for the Admiralty Inlet area and the wind advisories for
adjacent zones will continue until 1 AM.

Periods of cloudiness will continue tonight, then on Wednesday there
is a chance of showers as an upper trough digs to the east. A piece
of the upper trough along with some colder air aloft will linger
over the Inland Northwest until Thursday night, so afternoon showers
and thunderstorms near the Cascade Crest are forecast on Thursday
afternoon. The lowlands are forecast to be dry on Thursday. Highs
will be in the 60s Wednesday, warming to near 70 Thursday.

Temperatures will rise well into the 70s on Friday and skies will
be sunny as an upper ridge builds strongly offshore. Burke

.LONG TERM...Previous discussion...A warm and dry upper ridge axis
will pass directly over Western Washington on Saturday. The upper
ridge axis will be over Eastern Washington on Sunday. Cooling
seabreezes will strengthen at the immediate coast, but the rest of
Western Washington should have little change on Sunday. Some towering
cumulus and an isolated shower could form near the Cascade Crest
in the afternoon as a turn to light southerly flow aloft takes
place.

For Monday and next Tuesday, the long-range models are pretty
close with their 500 mb height values. The main difference is that
the GFS is a little more amplified with the pattern than the
ECMWF. So the GFS`s forecast of a stronger southerly component to
the upper flow is more supportive of late afternoon and early
evening shower/thunderstorm development along the Cascade Crest.
The ECMWF in contrast does not show this outcome, given its more
westerly component to the upper flow. For the lowlands, both
solutions are rain-free.  Haner

&&

.AVIATION...An upper level trof of low pres centered over British
Columbia will continue moving east overnight. The flow aloft will be
strong WLY. The low level flow will remain strong onshore. Expect
areas of MVFR CIGs to dvlp overnight.

KSEA...MVFR CIGs will probably persist until about 0900 UTC before
scattering out or lifting to near 5K FT. The convergence zone was
right over the area at this time; therefore, expect winds to be
variable 10 KT or less. Winds will probably back to sly overnight.

&&

.MARINE...
A 1040 mb high centered over the offshore waters along with lower
pres E of the Cascades will result in strong onshore or westerly
flow overnight. The offshore high will gradually weaken through FRI.
Therefore, expect the onshore flow to weaken with time.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...High Wind Warning until 1 AM PDT Wednesday for Admiralty Inlet
     Area.

     Wind Advisory until 1 AM PDT Wednesday for Eastern Strait of Juan
     de Fuca-Everett and Vicinity-San Juan County.

PZ...Storm Warning until 3 AM PDT Wednesday for Central U.S. Waters
     Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of
     Juan De Fuca.

 Gale WarningS are in effect for the remaining waters except
 the coastal waters.

 Small Craft Advisory in effect until 5 AM PDT Thursday for
 the Coastal Waters.

     Small Craft Advisory for rough bar until 9 AM PDT Thursday for
  Grays Harbor Bar.

&&

$$

www.weather.gov/seattle

An illustrated version of this forecast discussion can be seen at
www.wrh.noaa.gov/sew/gafd/latest_webafd.html



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