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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS66 KSEW 242212
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
312 PM PDT Fri Mar 24 2023

.SYNOPSIS...
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A cool and marginally active weather pattern will
remain over Western Washington through the weekend. Widely
scattered showers, with a chance of thunder and possibly a Puget
Sound Convergence zone Friday night will trend drier Saturday and
Sunday. Mountain snow or snow showers will continue through the
weekend. Colder temperatures will leave the door open for at a
chance of a rain/snow mix for some locations during the late
night and early morning hours Saturday and Sunday. Drier weather
is in store early next week.
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&&

.SHORT TERM /TONIGHT THROUGH MONDAY/...
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Scattered showers over the
area this afternoon will continue into this evening. There remains
a chance of isolated thunderstorms with this - especially along
the coast and interior south of Puget Sound. Increasing onshore
flow will elevate odds of the formation of a Puget Sound
Convergence zone late this afternoon and evening. Have included a
chance of thunder over Snohomish and King Counties this evening to
reflect the possibility of seeing lightning with the convergence
zone if it forms. In addition, both the HREF and UW HiRes ensemble
systems continue to show the possibility of persistent or heavier
showers in the convergence zone lowering the snow level -
resulting in some snow mixed in with convergence zone rain
tonight.While impacts aren`t expected, they remain possible and
folks traveling should be aware of the possibility. Ensemble
members that do develop a convergence zone show it developing late
this afternoon/early evening - between the I-90 corridor in King
County northward to US-2 in Snohomish County. In addition, the
cooler air mass over the region through the weekend will help
lower snow levels to below 1000 feet during the late night/early
morning hours going into Saturday and again going into Sunday.
This will allow for a broader potential for a rain/snow mix or
even just snow showers at those times - very limited
accumulations, if any at all, are possible.

Sunday will trend drier but with the broad trough still over the
region, showery weather will remain over the area - especially the
higher terrain. Even so, as is typical for this time of year -
even a few cloud breaks could boost high temps Sunday just north
of 50 for many areas in the interior.

Monday will see an upper level shortwave trough that has moved
down the British Columbia Coast slide southward well to the west
of Washington. This may provide some boost to clouds and even some
light precipitation for Western Washington - but in general the
idea is for another benign, mostly dry day Monday.

.LONG TERM /TUESDAY THROUGH FRIDAY/...Ensembles from the ECMWF, GEFS and CMC systems
consitstenly show the offshore upper level trough strengthening
as it digs southwared over the Eastern Pacific before moving
onshore somehwere over Southern Oregon into Northern California
Monday into Tuesday. This also equates to the some degree of upper
level ridging and drier weather building in over the Pacific
Nortwest midweek. Some potential for offshore low level flow will
help with less cloud cover high temperatures near normal - in the
mid 50s. The pattern may weeken late in the week opening the door
for a potential return of at least Spring showers toward the
latter half of the week.
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&&

.AVIATION...
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A broad upper level trough will remain centered over
Western Washington into Saturday producing light flow aloft. The air
mass is moist and somewhat unstable. Conditions will remain
predominantly MVFR across the area in scattered showers with any
improvements to VFR this evening likely to be brief. A convergence
zone will persist in the vicinity of KAWO/KPAE into the evening
hours.


KSEA...MVFR ceilings will persist across the terminal with scattered
showers. Any improvement to VFR late this afternoon/evening is
likely to be brief. Surface winds southwesterly 10 to 15
knots...with higher gusts this afternoon. Winds will ease somewhat
late this evening and remain S/SW 7 to 11 knots.  27
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&&

.MARINE...
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Small craft advisories continue most waters with
gales in the strait. High pressure building well offshore and lower
pressure over the interior will continue to produce onshore flow
into the weekend. The flow will then turn offshore early next week
as a surface low digs southward over the offshore waters. Seas of 14
to 17 feet across the coastal waters today will remain elevated into
Saturday before gradually subsiding back below 10 feet late in the
weekend. 27
-- End Changed Discussion --

&&

.HYDROLOGY...No river flooding expected in the next 7 days.

&&


.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory until 5 AM PDT Saturday for West Slopes
     North Central Cascades and Passes-West Slopes South Central
     Cascades and Passes.

PZ...Small Craft Advisory until 5 AM PDT Saturday 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-Grays Harbor Bar-West Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Gale Warning until 7 PM PDT this evening for Central U.S. Waters
     Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of
     Juan De Fuca.

     Small Craft Advisory until 11 PM PDT this evening for Admiralty
     Inlet-Northern Inland Waters Including The San Juan Islands.

&&

$$