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000
FXUS66 KSEW 171112
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
412 AM PDT Wed Apr 17 2024

.SYNOPSIS...
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Upper level ridge offshore today with dry northerly
flow aloft. Dry upper level trough moving down the backside of the
ridge over Western Washington late tonight into Thursday night.
Weak upper level ridge building over the area Friday with low
level offshore flow. Ridge dissipates Friday night with a
weakening front arriving Saturday afternoon and evening. Trailing
upper level trough moving through Saturday night into Sunday
morning. Upper level ridge building offshore Sunday night moving
over Western Washington Monday. The ridge will weaken Tuesday.
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.SHORT TERM /TODAY THROUGH FRIDAY/...
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Satellite imagery shows clear
skies over most of Western Washington this morning. Small patches
of stratus have formed over Snohomish county and along the North
Coast. With the mostly clear skies temperatures are quite cool for
the middle of April, in the upper 20s and 30s.

Upper level ridge offshore today with dry northerly flow aloft.
What little stratus there is out there will dissipate by late
morning. Even with the sunny skies temperatures aloft are a
little on the cool side which will keep highs mostly in the 50s
and lower 60s.

Upper level trough moving down the backside of the ridge will
reach Western Washington late tonight and remain over the area
into Thursday night. With the over land trajectory of the trough
there will be little moisture with it making for another sunny day
Thursday. Lows tonight and Thursday night in the 30s and lower
40s. Highs Thursday a little warmer, in the mid 50s to mid 60s.

Upper level trough moves off to the east Friday with an upper
level ridge building offshore. Low level flow going offshore with
gusty easterly winds in the Cascade Foothills. The offshore flow
and warming temperatures aloft will result in warmer high
temperatures Friday, in the 60s and lower 70s.

.LONG TERM /SATURDAY THROUGH TUESDAY/...Models in good agreement
with the upper level ridge moving through Western Washington
Friday night and a negatively tilted front approaching Saturday.
Front moving through Saturday afternoon and evening with rain
likely at that time. Trailing upper level trough will keep a
chance of showers in the forecast into Sunday. A weak upper level
ridge builds into Western Washington Monday for another dry day.
Model solutions diverging Tuesday with the ECMWF keeping dry
zonal flow aloft while the GFS has another front trying to move
into the area. Ensemble solutions are no help so with the
uncertainty will have chance pops in the forecast. Highs Saturday
in the upper 50s to mid 60s cooling Sunday to the 50s and lower
60s. A little warmer Monday and Tuesday, back into the upper 50s
to mid 60s. Felton
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.AVIATION...
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Clear skies and calm conditions persist early this
morning. KOLM is experiencing some lower visibilities due to mist at
the surface but should resolve after sunrise. Conditions remain VFR
through the TAF period, though cannot rule out a brief period of
MVFR stratus along the coast, potentially impacting HQM from 12-16Z
(30% chance). Onshore flow will continue to ease with light
northerly winds through the day Wednesday, generally 5-10 kt, with
gusts to 20 kt possible from 20-02Z at the Puget Sound terminals.

KSEA...VFR with southeasterly winds early this morning. SE winds
continuing through 16Z-17Z, then turning northerly after 18Z. Winds
pick back up 8 to 12 kt with occasional gusts to 20 kt possible
after 20Z, diminishing by 03Z.

Kristell

.MARINE...Northwesterly winds into today as surface high
pressure builds over the coastal waters. Winds will turn offshore on
Thursday and into Friday as a thermal trough develops along the
coast. Relatively calm winds expected through the rest of the week,
with the only exception being through the Central Strait of Juan de
Fuca, which may see periods of breezy winds Thursday and Friday. The
next frontal system will traverse the region on Saturday.
Waves will become less steep as seas decrease to 3 to 5 ft early
tomorrow and will remain there through the end of the week.

Kristell
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.HYDROLOGY...
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No river flooding expected for the next 7 days.
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.CLIMATE...
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The warmest 4 day stretch in April in Seattle began on
this day in 2016. Four straight days with highs in the 80s, 80 on
the 17th, the warmest April day on record 89 on the 18th, 84 on
the 19th and 81 on the 20th. Before this event Seattle had only
had back to back 80 degree days in April once, April 29 and 30,
1976 and the record for the most 80 degree plus days in the month
of April was 2 days ( 1947, 1976 and 1987 ). Felton
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.SEW WATCHES/WARNINGS/ADVISORIES...
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WA...Frost Advisory until 9 AM PDT this morning for Hood Canal Area-
     Lower Chehalis Valley Area-Southwest Interior.

PZ...None.
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$$