Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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712
FXUS66 KSEW 150242
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
742 PM PDT Mon Oct 14 2019

.UPDATE /THIS EVENING/...The calm before the storm this evening.
Forecast is on track and requires no updates at this time. Will
let overnight shift take a closer look at things for tomorrow.
Previous forecast discussion follows with updates to aviation and
marine sections. CEO

&&

.SYNOPSIS...A weak upper level ridge will move eastward and exit
the area by this evening. A frontal system will then approach
Western Washington and move inland on Tuesday. Wet and unsettled
weather will then continue through the week and into the weekend
as a series of systems move through.

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY/...Current satellite imagery
as well as a look out the window shows the morning low clouds
have burned off revealing mostly sunny skies for most locations
over W WA this afternoon. The exception to the rule seems to be
along the shores of the central Strait...around Port
Angeles...where some low clouds still linger. The good news is
that this patch is slowly thinning. Temperatures at the time of
this writing look to be mostly in the mid to upper 50s with
Bellingham and Seattle hitting 60. All in all...a nice fall day
and given the forecast...the last one for W WA for a stretch.

Models still on track for the upper level ridge to continue
moving eastward today with the ridge axis finally crossing the
Cascade crest around midnight tonight. This will hinder the
advance of the incoming frontal system a little...with the front
reaching the coast in the late morning or around noon but models
continue to consistently show this front will have trouble making
its way inland. Most locations should see dry conditions for much
of the day Tuesday before the front finally starts moving eastward
late in the afternoon with the best chances for precip holding
off until Tuesday evening or Tuesday night...depending on
location. Once the initial front works its way in Wednesday
morning it appears to begin to dissipate over the area. Under
normal circumstances...this would be encouraging /unless you like
rain/...but a secondary front hot on its heels passes through
Wednesday afternoon and evening. This second front proves to hold
together much better and thus will keep rain in the forecast for
much of the day. This one/two punch in terms of fronts looks to
also bring breezy to windy conditions to the area. While the
strongest winds are expected to be in the usual favored
spots...along the coast and in the north interior...some spots
along the Sound will also see some breezes kick up. Models
continue to show wind speeds falling just short of any headline
criteria at this time...but will need to monitor as current
solutions are inching closer to said criteria.

High temperatures here in the short term look to remain mild
generally in the upper 50s to around 60. Overnight lows will see a
significant change though...going from some brisk lower to mid
40s /and some isolated locations dipping down into the upper 30s/
tonight to upper 40s to lower 50s Tuesday night thanks to the
increased cloud cover as a moderating influence. SMR

.LONG TERM /THURSDAY THROUGH SUNDAY/...Late Wednesday night and
into Thursday morning models suggest there may be some scattering
out of precip...the GFS indicating it a bit better than the
ECMWF...but both models agree that the next frontal system and
associated upper level trough follows so quickly that to even
suggest either a break or brief transition to showers would be
folly. Instead...sufficed to say the wet and active conditions are
expected to continue throughout the extended as a veritable conga
line of systems make their way through W WA as upper level low
pressure holds court over the western Canadian coast. This will
serve to lower daytime highs down into the lower to mid 50s for
lowland locations but overnight lows will remain stable in the mid
to upper 40s...with some valleys in the SW interior possibly
dipping down into the lower 40s. SMR

&&


.AVIATION...Westerly flow aloft this evening will shift to the
southwest on Tuesday as upper level ridge departs and system
approaches the coast. Air mass this evening is dry and stable with
relatively light surface winds. Mid and high level clouds will
continue to increase into Tuesday with rain appearing on the coast
during the late morning to afternoon hours and inland throughout
the evening. VFR conditions tonight will give way to MVFR (locally
IFR) cigs Tuesday afternoon and evening as rain spreads inland.
Winds will also become breezy by the end of the TAF period.

KSEA...VFR conditions through the period. High clouds will
continue to thicken and lower into a mid level deck Tuesday.
Ceilings will lower further as rain develops Tuesday evening.
Light winds will increase Tuesday evening into Tuesday night as
secondary front approaches.

&&

.MARINE...A strong front will reach the coastal waters by Tuesday
afternoon and shift inland during the evening and overnight hours.
Current headlines remain in place (gale warning for coastal waters
and small craft for inland waters). Periods of blustery weather
will continue for the rest of the week as additional weather
systems move through the waters. Additional headlines will likely
be needed. Seas will also build along the coast to 15 to 20 foot
range for the latter half of the week. CEO

&&

.HYDROLOGY...A series of wet systems moving through the area
Tuesday into the weekend will cause rivers to rise, but flooding
is unlikely over the next seven days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Gale Warning from 6 AM to 11 PM PDT Tuesday for 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.

     Small Craft Advisory from noon Tuesday to 5 AM PDT Wednesday for
     Admiralty Inlet-East Entrance U.S. Waters Strait Of Juan De
     Fuca-Northern Inland Waters Including The San Juan Islands-
     Puget Sound and Hood Canal.

&&

$$

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