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094
FXUS66 KSEW 190957
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
257 AM PDT Wed Jun 19 2024

.SYNOPSIS...High pressure aloft will gradually build through the
week, allowing conditions to dry out and warm up. A pattern change
is on track for the weekend as a trough brings wetter and cooler
conditions to western Washington.

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.SHORT TERM /TODAY THROUGH FRIDAY/...
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Mostly clear skies in place
over W WA this early morning as the area finds itself more under the
influence of an upper level high over BC as opposed to the weak
troughiness to the south. As this high remains fairly stationary for
the remainder of the work week, dry conditions will persist with
warming temperatures through Friday. Daytime highs today will get
into the mid to upper 70s for most of the interior lowlands while
the coast and most water adjacent areas will see highs in the mid
60s to right around 70. Surface level high pressure over southern BC
will set up an offshore flow pattern Thursday, further boosting
temperatures in what will be the warmest day all around with most
lowlands seeing highs in the mid 70s to lower 80s. Start seeing
hints of the return to onshore flow starting Friday, as coastal and
water adjacent locations return to the mid 60s to around 70 while
the interior remains toasty with highs once again in the mid 70s to
lower 80s.

While the majority of the CWA will be dry, it is worth mentioning
that some lingering moisture and instability over the
Cascades...particularly the North Cascades, will still run the risk
for some afternoon and evening scattered showers and possibly some
isolated thunderstorms. Rainfall with any of these showers or
thunderstorms is expected to be generally light.

Lastly, this discussion of warming temperatures once again turns
attention to heat risk potential. Even with the high temperatures
mentioned above, overnight lows will continue to cool down into the
lower to mid 50s throughout the area. While there are pockets of
moderate HeatRisk...mainly confined to the Seattle metro area and
some of the Cascade valleys, current data suggests widespread heat
impacts are expected to be minimal at this time.

18


.LONG TERM /SATURDAY THROUGH TUESDAY/...An incoming frontal system
associated with an upper level low dipping south from the Canadian
coast hints at a little bit of a pattern change for the weekend and
the beginning of next week as the low mostly sits and churns in
place, pushing at least a couple of fronts through the area. This
will take a degree or two off daytime highs Saturday but will knock
temps back into the 60s for most locations Sunday and Monday...with
some recovery back to the lower 70s Tuesday. PoPs during this time
frame are less than impressive however, with most of the CWA only
seeing chances ranging from the single digits to around 20-30 pct
Monday morning. Instead, the coast and northern tier of the CWA
appear to be favored, where PoPs there will peak in the 40 to 50 pct
range both Sunday and Monday. Tuesday sees activity starting to wind
up...but PoPs will still linger in the 10-20 pct range for the
aforementioned favored locations.

18
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.AVIATION...
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Weak upper level trough over Western Washington into
Thursday morning with light flow aloft. Surface high pressure
centered off British Columbia with northwesterly surface gradients.

Clear skies over Western Washington into Thursday with patchy
fog/low clouds along the coast 12z-15z.

KSEA...Clear skies. Northeast wind 6 to 10 knots becoming
northwesterly around 21z. Winds switching back to northeasterly
after 06z. Felton
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.MARINE...
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High pressure centered off British Columbia today
will move south tonight and Thursday with weak onshore flow. Onshore
gradients increasing later Friday with surface high pressure over
the coastal waters ahead of weak system arriving over the weekend.
Gale force westerlies possible in the Central and Eastern Strait of
Juan de Fuca Friday night with small craft advisory winds in the
adjacent waters. Small craft advisory westerly winds in the Strait
Saturday evening. Felton
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&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&

$$