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FXUS66 KSEW 152209
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
300 PM PDT Sat Jun 15 2019

.SYNOPSIS...No significant weather systems will affect the area into
the first part of next week. Marine layer clouds will occasionally
spread into Western Washington. An upper trough will reach the
area around the middle of next week for a chance of showers, mainly
in the Cascades.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...Marine clouds have receded to
along the coast while the majority of W WA is under sunny skies with
a stray cloud here and there. Temperatures look to be on track with
inherited forecast...with locations along the coast and Strait
running at about what they were this time yesterday while interior
locations running a few degrees warmer.

Models remain pretty consistent regarding the short term...with the
upper level ridge making its way east through the day Sunday. Both
GFS and ECMWF are hinting at a shortwave disturbance within the
ridge that might allow for some showers...but bulk of activity stays
north of the border with only a little bit dipping down into the far
northern Cascades...but even that looks more like it will impact the
eastern slopes as opposed to the western slopes within the CWA.
Still...current forecast allows for a little spill-over in PoPs just
in case. Flatter ridging will set up over the area Monday with high
temperatures being identical to those expected tomorrow...lower to
mid 60s along the coast...mid to upper 70s for the interior.
Continued onshore flow will allow for overnight and early morning
marine stratus to persist throughout the near term with sunny skies
expected to emerge by afternoon. SMR

.LONG TERM /TUESDAY THROUGH FRIDAY/...Tuesday appears to be nothing
to write home about...although models are in a bit of disagreement
with the ECMWF trying to bring in some showers in advance of the
upper trough expected for Wednesday. The GFS hints at this...but
does not bite on quite as hard as the ECMWF. Opted not to go full
bore on the ECMWF solution...but did go with high-end slight chance
PoPs for now. This is where the models start to branch off...with
the ECMWF bringing the upper level trough further south for
Wednesday and Thursday...potentially bringing precip area-wide while
the GFS seems convinced that the bulk of this feature will remain to
the north with possibly some showers popping up over the Cascades.
Given this uncertainty and...as per the previous shift...previous
runs of the models were a bit more in lock step...decided to lean
more into the inherited forecast while splitting the difference
between the apparently now dueling models in the hopes that
solutions might realign. Models agree on generally dry conditions
for Friday but for different reasons...the ECMWF returns some
ridging to the area while the GFS has a dry secondary trough in
place. SMR

&&

.AVIATION...Weak upper ridge axis over the offshore waters will
shift onshore late today with light northwest flow aloft
becoming westerly. The air mass is stable and dry with the
exception of a marine layer along the coast that will push
partially inland overnight. Areas of IFR in stratus/fog will develop
at the coast this evening and move inland overnight...perhaps as far
as the south end of Puget Sound and the Kitsap Peninsula by 12Z
Sunday. VFR expected away from the immediate coast from mid-morning
Sunday through the evening.


KSEA...VFR continuing through the overnight hours. Expecting stratus
to fall short of reaching KSEA on Sunday morning, but it might get
close around 12Z-15Z. Surface winds N to NW 5 to 10 knots...becoming
light and variable late tonight. 27

&&

.MARINE...High pressure over the coastal waters with lower
pressure inland will result in varying degrees of onshore flow
through the middle of next week. At least small craft westerlies
will developing in the late afternoon/early evening hours in the
central and eastern Strait of Juan de Fuca each day. A stronger
onshore push Sunday evening has the potential to produce a westerly
gale in the Strait and have decided to go with a gale watch there.
Small craft advisory winds also expected over the coastal waters
tonight as well as waters adjacent to the east entrance of the
strait. 27

&&

.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed
until then.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 6 PM this evening to 5 AM PDT Sunday
for Central U.S. Waters Strait Of Juan De Fuca-Coastal
Waters From Cape Flattery To James Island 10 To 60 Nm-
Coastal Waters From Cape Flattery To James Island Out 10 Nm-
Coastal Waters From James Island To Point Grenville 10 To
60 Nm-Coastal Waters From James Island To Point Grenville
Out 10 Nm-Coastal Waters From Point Grenville To Cape
Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville
To Cape Shoalwater Out 10 Nm-East Entrance U.S. Waters
Strait Of Juan De Fuca-Northern Inland Waters Including The
San Juan Islands.

Gale Watch from Sunday afternoon through late Sunday 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 6 PM this evening to 2 AM PDT Sunday
for Admiralty Inlet.

&&

$$

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