Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 261007
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
305 AM PDT Fri May 26 2017

.SYNOPSIS...An upper ridge will bring dry and warmer weather
through Memorial Day. Onshore flow will develop Monday night or
Tuesday resulting in a cooling trend and a chance of showers by the
middle of next week.

&&

.SHORT TERM...Another clear night over much of W WA this early
morning with temperatures ranging from the mid 40s to lower 50s but
with upper level ridging ready to build into the area for the
holiday weekend...safe to say the term cool will temporarily exit
the collective vocabulary for the next few days. Highs today look to
creep right up against the 80 threshold for the interior and then
only rise from there...with highs Saturday through Memorial day
entering into the low to mid 80s. This may result in heat level
concerns and as such will likely issue a special weather statement
to go along with the morning forecast package to highlight the
potential impact of heat related issues. Future shifts will need to
make the call on whether or not any additional products will be
needed.

With upper level ridging in place for the near term...pretty safe to
say that any prospects for rain will be very very minimal. Models do
hint at a touch of instability over the Cascades for late Sunday
afternoon and early Sunday evening that might result in a stray
convective shower or thunderstorm...though did opt to leave out
thunderstorm wording in forecast at this time given such low pops
associated with the feature.

Models start to diverge when it comes to Monday...oddly enough with
the GFS being the wetter solution featuring a more progressive exit
of the upper level ridge as the ECMWF wants to hold the ridge over
the area for another 24 hours. Looking at the surface...GFS starts
off a marine push Monday evening which looks to trigger some
scattered convective showers. With the ECMWF solution inconsistent
with its previous runs and the already discussed GFS solution
remaining consistent with its previous runs...am content to remain
with thinking Monday will serve as a transition day and thus leaving
inherited forecast trend in place.  SMR

.LONG TERM...Onshore flow on Tuesday will allow for a slight cooling
of temps...on average 4-8 degrees cooler than highs on Monday...as
well as a continued threat of scattered convective showers. An upper
level trough looks to make its way toward the area Wed
afternoon...pulling temps down further...yet still remaining above
seasonal normals...and gradually increasing pops over the area. By
Thursday...chance pops look to be in place over the area as the
trough axis makes its way eastward. A series of quick moving troughs
will follow...making for unsettled weather for next weekend.  SMR

&&

.AVIATION...A ridge of high pres will prevail over the region today
for light nly flow aloft. The low level flow will remain weak
onshore. Local IFR CIGs/VSBYs over mainly the coast will dissipate
by 1800 UTC.

KSEA...VFR. Winds will be light nly.

&&

.MARINE...
High pressure offshore with lower pressure inland will result in
light onshore flow through this weekend. Expect the onshore flow to
strengthen on Monday for the possibility of gale force winds over
parts of the Strait of Juan de Fuca.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 6 PM this evening to midnight PDT
     tonight for Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$

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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