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089
FXUS66 KSEW 131049
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
349 AM PDT Thu Jun 13 2024

.SYNOPSIS...
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Upper level ridge moving through Western Washington
today. Cool upper level low dropping down from the Gulf of Alaska
approaching the area Friday. Weak front spinning out of the low
moving through later in the day. Cool unsettled weather over the
weekend as the low moves right over the area. The low will move
south and east Monday. A weak upper level ridge will try to build
for the middle of next week.
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.SHORT TERM /TODAY THROUGH SATURDAY/...
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Satellite imagery shows
mostly clear skies over the area at 3 am/10z. Temperatures were in
the mid 40s to mid 50s.

Upper level ridge moving through Western Washington today giving
the area a mostly sunny day. Southwesterly flow aloft will bring
in some high clouds especially this afternoon. Highs will be near
normal, 60s and lower 70s.

Ridge well to the east tonight with an upper level low making its
move out of the Gulf of Alaska towards Western Washington. Low
still well to the northwest by early Friday morning. With mostly
clear skies temperatures will lower into the 40s and lower 50s by
sunrise Friday morning.

Upper level low continuing to move southeast Friday. Weak front
spinning out of the low moving through during the day with showers
along the coast, in the Olympics and Northwest Interior with a
chance of showers elsewhere. Highs with plenty of cloud cover will
only get into the upper 50s to mid 60s.

Low continuing to move towards Western Washington ending up right
on top of the area Saturday. Increasing showers late Friday night
through Saturday. Air mass becoming unstable with 500 mb
temperatures as cold as -28C. Lapse rates in the plus 7 to 8C
range and lifted indexes below 0 Saturday afternoon for a chance
of thunderstorms. Lows Friday night in the 40s. Highs Saturday
only in the mid 50s to lower 60s, at least 10 degrees below
normal.

Upper level low remaining over the area Saturday night with
showers and a chance of thunderstorms continuing through the
evening hours.

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Models solutions starting
to lose some consistency as far as the timing of when the upper
level low moves out of the area. Models remaining consistent with
the low over Western Washington Sunday continuing the chance for
showers and possible thunderstorms. The operational GFS is now
keeping the low around well into Monday while the ECMWF kicks the
low out to the south and east like previous model runs have
indicated. GFS ensembles more in line with the ECMWF solution
than the operation GFS solution so will stay with just a chance of
showers Monday. Both models have Western Washington on the
backside of the low Tuesday with a slightly unstable air mass over
the region keeping a chance of showers in the forecast. Weak
upper level ridge trying to build Wednesday. The ridge is pretty
feeble in the ensembles with 20 to 30 percent of the ensemble
solutions still having some light showers in the area Wednesday.
Would like to see a stronger ridge before completely drying out
the forecast for the middle of next week. High temperatures
warming a little each day with mid 50s to lower 60s Sunday warming
to near normal, mid 60s to lower 70s, Wednesday. Felton
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.AVIATION...
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Westerly flow aloft becoming southwesterly as an upper-
level trough approaches western Washington. Skies are mostly clear
this morning except for some passing high clouds. With the mostly
clear skies and upper-level subsidence, some patchy fog development
will be possible, but should be shallow, patchy, and localized to
river valleys. A marine stratus layer may develop this morning, with
up to a 30-35% chance of MVFR or lower ceilings at HQM. Tomorrow
skies will be prevailing VFR conditions with increasing mid to high
level clouds as a frontal system approaches the region. Light
northerly winds will pick up this afternoon to around 5-10 kt,
switching to southerly late tonight towards the end of the TAF
period.

KSEA...VFR conditions through the TAF period. Mostly clear this
morning with increasing mid to high level cloud cover through the
afternoon and evening hours ahead of an incoming system. Northerly
winds 5 to 10 kt through the day then switching to
south/southwesterly around 06Z Friday.

LH
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.MARINE...
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High pressure dominates over the coastal waters this
morning which has allowed for mostly light winds across the area
waters today. A westerly push down the Strait of Juan de Fuca will
warrant a Small Craft Advisory for the Central and East Strait
beginning late this afternoon through early morning Friday.

A frontal system will approach the region Friday morning, with the
low pressure center moving through on Saturday into early Sunday.
Additional pushes of westerlies down the Strait of Juan de Fuca are
expected Friday evening and Saturday evening, which may warrant
additional headlines. Winds look to remain below advisory thresholds
through the remainder of the area waters. Scattered thunderstorms
are possible Saturday over the Puget Sound and Hood Canal region,
which could produce heavy downpours, lightning, small hail, and
brief gusty winds.

The pattern looks uncertain heading into early next week, but high
pressure may briefly build back into the coastal waters with
additional systems weakening as they approach and move through the
region.

Seas look to remain around 5-7 ft through the forecast period.

LH
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.SEW WATCHES/WARNINGS/ADVISORIES...
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WA...None.
PZ...Small Craft Advisory from 2 PM this afternoon to 5 AM PDT Friday
     for Central U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 5 PM this afternoon to 5 AM PDT Friday
     for East Entrance U.S. Waters Strait Of Juan De Fuca.
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