Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 221537

Area Forecast Discussion
National Weather Service Seattle WA
845 AM PDT Tue May 22 2018

.SYNOPSIS...An upper ridge over the area today will slowly drift
east Wednesday and Thursday. Temperatures will remain warm through
Wednesday and then a little cooling will occur Thursday with light
onshore flow. Increasing southerly flow aloft on Wednesday will
bring a chance of showers to the mountains. A weather system
will bring cooler weather and a chance of showers Friday and
High pressure might build into the area for Sunday and Monday.


.SHORT TERM...Areas of morning fog and low clouds are on the coast,
in the Strait of Juan de Fuca, and all around Admiralty Inlet and
Whidbey Island--with a few patches elsewhere. Sunny skies and warm
temps are expected through Wednesday, and then some onshore flow will
develop and temps should cool into Thursday. There is a chance of
showers near the Cascade crest Wednesday afternoon and evening.

.LONG TERM...Extended models in good agreement for most of the
extended on the 00z run with some changes to the forecast. Upper
level low to the south of the area moving inland about 12 to 18
hours faster than previous runs. This will increase the cloud
cover over western Washington on Friday with a chance of showers
by afternoon. Highs will cool into the 60s for the entire area.
Upper level trough moving into the area Friday night and Saturday
keeping the mostly cloudy chance of showers forecast going into
the first part of the holiday weekend. Weak front moving by to the
north on Sunday. Current run has this system getting pushed far
enough to the north to keep precipitation out of the area. Would
like to see another run or two of this solution before drying out
Sunday. Model solutions are a little different for Memorial day
with the GFS putting some weak trofiness off the coast with
southwesterly flow aloft while the ECMWF builds a flat ridge into
the area. Both models are dry with low level onshore flow so at
least right now Memorial day looks like a pretty typical late May
day with morning clouds and afternoon sun with highs in the 60s
and lower 70s. Felton


.AVIATION...Light northerly flow aloft this morning will become
light east-southeasterly this afternoon and evening as an upper
level ridge axis near the coast shifts into the interior of British
Columbia. The air mass is dry and stable except for areas of low
level moisture near the coast and Strait of Juan de Fuca. Low level
onshore flow continues and will peak during the late afternoon and
evening hours. VFR conditions in place over much of W WA this
morning save for IFR conditions present over the north coast and
along the Strait of Juan de Fuca. Cigs there are expected to improve
by late this morning to VFR conditions as low level moisture/clouds
burn off. However...given the current weather pattern...low clouds
are expected to return to these locations late tonight and into
Wednesday morning.

KSEA...VFR conditions expected to continue over the next 24 hours.
Surface winds north-northwest 5 to 10 knots...becoming southwest
early Wednesday morning. 27/SMR


.MARINE...High pressure will remain offshore through Saturday with
lower pressure east of the Cascades, maintaining onshore flow. Small
craft advisory westerlies are likely in the central and eastern
Strait of Juan de Fuca again late this afternoon through early
Wednesday morning.

Onshore flow will be stronger Wednesday and Wednesday night, and
there is a good chance of gale westerlies in the central and
eastern Strait, along with small craft advisory winds in the
adjacent waters of Admiralty Inlet and the Northern Inland Waters.
A gale watch remains in place for the aforementioned portions of the
strait. Will likely wait a bit before adding headlines for the
adjacent waters.  McDonnal/SMR


.CLIMATE...With an average temperature of 60.9 degrees this has
been the warmest first 3 weeks of May on record in Seattle. Warm
starts to May have been common the last few years. The second
warmest first 3 weeks of May in Seattle 2013 ( 60.2 ), 3rd
warmest 2016 ( 60.1 ) and 4th warmest 2014 ( 58.9 ). Records
started at Sea-Tac airport in 1945. Felton


PZ...Gale Watch from Wednesday afternoon through late Wednesday night
     for Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 3 PM this afternoon to 3 AM PDT
     Wednesday for Central U.S. Waters Strait Of Juan De Fuca-
     East Entrance U.S. Waters Strait Of Juan De Fuca.


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