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000
FXUS66 KSEW 212122
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
222 PM PDT Sun Apr 21 2024

.SYNOPSIS...Westerly flow aloft through this afternoon with
lingering showers before drier conditions beginning tonight.
Ridging will build over the Pacific Northwest Monday and Tuesday
with drier weather and warming temperatures. Troughing will
develop over the area later Wednesday into the weekend for more
unsettled weather.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...Showers continue this
afternoon with westerly flow aloft as an upper trough moves east
of the area and ridging begins to build offshore. Showers will
dissipate this evening into tonight, before cooler, drier
conditions into Monday morning. Clearing skies, along with lighter
winds, will allow lows to drop into the mid 30s to low 40s. A
Frost Advisory remains in effect for the East Puget Sound
Lowlands, as well as portions of the Southwest Interior, with
temperatures likely ranging 33 to 37 degrees into Monday morning.
Make sure to bring sensitive plants indoor, or cover them.

Ridging will build further across Western Washington on Monday for
dry conditions, and warming temperatures. Generally clear skies
are expected on Monday. Clouds will begin to increase Monday night
into Tuesday with increasing southwesterly flow as the ridge axis
moves eastward. However, dry conditions are expected to continue
into Tuesday given the ridging influence. Highs on Monday will
warm into the upper 50s to mid 60s, with highs warming to near 70
for some areas on Tuesday.

Onshore flow will increase Tuesday night into Wednesday with
troughing developing across British Columbia. Precipitation
chances also increase on Wednesday given the proximity of the
trough. Clouds and increased shower chances will usher in cooler
temperatures with highs in the mid to upper 50s.

.LONG TERM /THURSDAY THROUGH SUNDAY/...Troughing will develop
further over the Pacific Northwest Thursday through Saturday.
Unsettled weather during this period is expected with increased
precipitation chances and periods of light mountain snow.
Uncertainty begins to increase on Sunday, however, the majority of
ensembles suggest troughing develops again offshore for continued
precipitation chances, although at this time precipitation
amounts are not significant. Temperatures during this period will
likely lean a few degrees below normal given troughing over the
area. JD

&&

.AVIATION...Post frontal showers continue across all terminal areas
this afternoon. A convergence zone has setup from south of Bremerton
to Seattle this afternoon, which caused a change in wind direction
to the north for areas under this convergence zone. Variable winds,
and lower CIGs/VIS are possible with all showers this afternoon
(particularly with the convergence zone). Showers will end from west
to east this afternoon and evening, revealing VFR conditions region-
wide for the remainder of the TAF forecast with scattered to broken
CIGS through Monday morning. Northerly winds have arrived this
afternoon for terminals in Puget Sound (albeit KBFI still seeing
south winds in between KSEA and KPAE). Remaining areas will see
predominately west winds through Monday, with more of a northeast
component expected on Monday, Occasional gusts up to 20 kt are
expected through Sunday evening.

KSEA...Convergence showers developed over the terminal this
afternoon. Hi-res guidance has activity continuing through 02-03Z
this evening. Winds have switched to the north as a result and have
gusted up to 20 kt this afternoon. MVFR CIGs/VIS are possible at
times with the shower activity. Once showers dissipate, winds will
remain northerly and diminish to around 5 kt overnight, before
increasing to 10 kt Monday. CIGs are expected to scatter out
tonight/Monday.

HPR

&&

.MARINE...High pressure continues to build offshore over coastal
waters today. With a cold front still to the east of the Cascades,
strong onshore flow will continue gusty winds in the Central/East
Strait of Juan de Fuca through tonight (small craft advisory will
continue). Expect the ridge to shift inland Monday with a thermal
trough underneath along the coast. The flow will turn northerly and
easterly. Winds up to 20 kt are possible in the central strait
Monday afternoon, as well as Puget Sound waters. An additional front
arrives Tuesday night/Wednesday, with additional systems possible
late week.

Seas have decreased to 6 to 8 feet this afternoon in the coastal
waters, and will drop to around 4 to 6 feet through the remainder of
the week.

HPR

&&

.HYDROLOGY...No river flooding is expected over the next 7 days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Frost Advisory from 11 PM this evening to 8 AM PDT Monday for
     East Puget Sound Lowlands-Hood Canal Area-Lower Chehalis
     Valley Area-Southwest Interior.

PZ...Small Craft Advisory until midnight PDT tonight for Central U.S.
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
     Strait Of Juan De Fuca.

&&

$$