Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 161548
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
848 AM PDT Sun Apr 16 2017

.SYNOPSIS...An upper ridge will bring warm temperatures and partly
sunny skies to the area today. This will quickly be followed by an
upper low bringing clouds and a chance of light precipitation to
Western Washington tonight. Wet conditions will prevail Monday
afternoon through Wednesday as three fronts cross the area.
Conditions will improve towards the end of the week.

&&

.SHORT TERM...
High pressure aloft will prevail over the region today. Expect
primarily high clouds to stream across the area ahead of the next
low pressure system. Temps across much of the lowlands will climb
into the lower 60s this afternoon, thanks to low level offshore
flow.

Speaking of said low...will start to see pops associated
with that creep into the area by late this afternoon/early this
evening. As the low moves eastward during the overnight hours...bulk
of the moisture remains south and east of the CWA...with southern
most portion of the CWA and the SE Cascades seeing the best chances
for precip with this system.

Unfortunately...the remainder of the area will not have long to wait
before higher pops rear their ugly head once more...this time as a
frontal system pushes onshore from an upper level low well out over
the Pacific waters. That will bring rain over the area for much of
Monday and into Monday night. A weak upper level ridge may
transition rain to showers during the overnight hours Monday and
into very early Tuesday morning...but a secondary front associated
with this system will bring yet another round of rain to the area.
SMR/05

.LONG TERM from the previous discussion...Tuesday night brings
another weak upper level ridge to the area which may result in a
brief 6-12 hour dry period before a third front associated with this
upper low makes its way onto the coastline Wed morning. At least at
this point the upper low responsible finally starts to make its way
east...although this will not do anything to ease the rain fatigue
that has likely gripped most of the area by this point in the
forecast. Models still look on track for conditions to dry late
Thursday night as an upper level ridge builds into the
area...resulting in a dry Friday.

Although...it should be no surprise what looms for Saturday as the
active pattern continues... SMR

&&

.AVIATION...An upper ridge will cross the area today. An upper
trough will move up from the southwest tonight. The flow aloft
will be mainly southwest through tonight. At the surface, high
pressure to the north and east will produce offshore flow today. A
weak surface trough will move into the area tonight. The air mass
is stable with high level moisture. Ceilings will lower tonight
as moisture increases from the south. Mid clouds should increase
this evening then low clouds Monday morning.

KSEA...High clouds today. Mid clouds this evening. VFR low clouds
late tonight. MVFR low clouds are possible Monday morning. North
wind 10-20 knots will ease this evening and then become south
after midnight tonight. Schneider

&&

.MARINE...High pressure to the north and east will give offshore
flow today. Small craft advisory easterly winds will occur near
the West Entrance Strait of Juan De Fuca. Marginal small craft
advisory northerly winds are also possible for much of the inland
waters today but the forecast is 10-20 knots for now.

Northeasterly offshore flow will switch to southerly onshore flow
tonight as a trough moves up from the south. A series of frontal
systems will move through the waters Monday through Wednesday
night with small craft advisory winds for the Coastal Waters at
times during this period. High pressure will move over the area
later Thursday. Schneider

&&

.HYDROLOGY...
River flooding is not expected the next 7 days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 6 PM PDT this evening for Coastal
     Waters From Cape Flattery To James Island Out 10 Nm-West
     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.weather.gov/seattle/gafd/latest_webafd.html



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