400
FXUS66 KSEW 261530
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
830 AM PDT Wed Jun 26 2024

.UPDATE...Quick update to add thunderstorm mention this morning
along the Cascade crest. Mid-level instability remains a bit
stronger than expected and the leading moisture is producing
clusters of isolated thunderstorms near the Cascades from south
to north this morning. Expect this trend to continue with gusty
winds and lightning as the predominant threat from these storms.
Meanwhile, more widespread precipitation continues to move east
into the Olympic Peninsula this morning ahead of the approaching
front. Cullen

&&

.SYNOPSIS...A shift in the pattern will bring the next upper
trough to the Pacific Northwest, bringing cooler temperatures,
breezy winds, and the return of precipitation today and Thursday.
Isolated thunderstorms are also expected near the Cascades today. The
cycle then repeats with dry and warmer conditions Friday ahead of
the next disturbance that reaches the area over the weekend.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...A pattern change brings
cooler and wetter weather back to western WA as an upper level low
moves through the Pac NW. For today, showers will be mostly
concentrated along the coast and in the mountains with just
isolated to scattered coverage in the interior. The air mass is
most unstable along the Cascade crest and there is a chance of
thunderstorms too, especially in the North Cascades. We`re in
post-frontal onshore flow tonight with ongoing showers and a
convergence zone over the north sound. Winds will be gusty in the
central interior and south sound in the 20-30 MPH range. With the
cooler air mass in place, temps will drop a few degrees cooler
than average with highs in the 60s along the coast and near 70 in
the interior.

Onshore flow continues into Thursday as the upper low shifts
slowly E/NE toward southern Alberta. For western WA, plenty more
showers, especially over the coast and mountains, as the low
level air mass remains moist. Convergence zone showers will
continue too, focused along the King/Snohomish line. Temperatures
will continue to trend below average with highs in the 60s.

High pressure rebuilds over the region on Friday as the upper low
departs. Look for drier weather with near average temps. 33

.LONG TERM /SATURDAY THROUGH TUESDAY/...Blocking high pressure,
centered over the Rockies, keeps systems offshore as we move into
Saturday. Wetter weather returns again Saturday night and Sunday
as the ridge shifts east and a trough rotates through western WA.
Weak high pressure nudges inland early next week with a few light
showers mainly over the coast and mountains. 33

&&

.AVIATION...South-southwesterly flow aloft this morning as an
upper level trough approaches W WA along with a associated cold
front at the surface. Mid and high level clouds continue to stream
into the region ahead of the aforementioned front and radar this
morning shows widespread precipitation gradually making its way
inland along the coast. Thunderstorms have also started to move
up from the south along the Cascade crest this morning and will
continue to make their way northward over the next few hours.
Current conditions at the majority of the TAF sites remains VFR
this morning, with .MARINE...
the exception of MVFR conditions at KHQM as
rain starts to move in. Ceilings along the coast and southwest
interior have already started to lower, but expect overall
ceilings across the interior to gradually lower through the
afternoon and evening as the front crosses over the area. Latest
guidance suggests ceilings lowering to MVFR across the interior
terminals after 00z. A few localized pockets of IFR to LIFR will
be possible in any heavier showers. Expect lower ceilings to
continue across the region through the evening and into most of
the overnight hours as showers persist throughout the area.

Winds have transitioned back to the S/SW and will increase to
around 12 to 17 knots, with gusts up to 20 to 25 knots possible
throughout the afternoon. Winds will start to gradually ease up to
8 to 12 knots around 04z-06z.

KSEA...VFR conditions will continue through the first part of the
day. Winds have transitioned to S/SW this morning and will increase
to around 12 to 16 knots between 15-18z. Gusts around 20 to 25
knots will be possible at times through the afternoon. Rain
showers will start to move through the terminal 04z-06z with
ceilings expected to lower to MVFR through the overnight period.

Maz/Borth

&&

.MARINE...A frontal system will move through the area waters this
morning and into the afternoon, with breezy south-southwesterly
winds throughout the interior waters. Guidance still shows small
craft advisory strength westerlies through the Strait of Juan De
Fuca this morning through the afternoon, maintaining around 20 to
30 kts. Southerlies will also increase throughout the Puget Sound
waters this afternoon (15 to 25 kts) before gradually decreasing
into the evening as the front passes through.

Weak high pressure looks to build offshore briefly throughout the
end of the week, with diurnal pushes down the Strait likely at
times. Additional systems look to push through the area waters
through the weekend and into the first part of next week.

Coastal seas 3 to 5 feet this morning will generally maintain
through Friday, before increasing to 4 to 6 feet over the weekend.

Maz

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 11 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 9 PM PDT this evening for Admiralty
     Inlet-Puget Sound and Hood Canal.

&&

$$