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000
FXUS66 KSEW 122150
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
250 PM PDT Fri Apr 12 2024

.SYNOPSIS...Weak high pressure will begin to build over the region
and last throughout the weekend, bringing with it a warming
and drying trend. Upper-level troughing returns on Monday with
showers and cooler temps. This will only be a brief interlude as
upper level ridging is expected to return for much of next week.

&&

.SHORT TERM /TONIGHT THROUGH MONDAY/...Current satellite shows most
of the low clouds that been present this morning have since lifted
and/or scattered out. The only place they continue to linger is
along the Strait of Juan de Fuca, where they cling tenaciously.
While that is serving to keep that area cool, the remainder of W WA
is warming with 2 PM PDT temps generally in the mid to upper 50s
with a few isolated lower 60s out there. As such, inherited high
temp forecast for today looks to be on track.

Weak upper level ridging will be the main headline for the short
term, not only making for dry conditions but also with warmer
daytime highs. Mid 50s to around 60 expected in the interior
lowlands today then warming even further to the lower to mid 60s for
Saturday. A little cooling is expected Sunday ahead of the next
frontal system...most notably along the coast where temps will cool
back into the mid to upper 50s while the interior remains warm with
highs in the upper 50s to lower 60s.

The next chance for rain could sneak into the area as early as
Sunday night...mainly in the higher elevations...but more widespread
rainfall looks to hold off until a dissipating front passes through
the area throughout the day Monday. Neither deterministic nor
ensemble models seem particularly wowed by this system with
deterministic models appearing to be rather splotchy with precip
while ensembles lean toward fairly small precip amounts...generally
under one-tenth of an inch. This system will knock temps down a bit
to just a degree or two below normal with daytime highs in the lower
to mid 50s.

Overnight lows throughout the near term are pretty uniform with each
night getting down into the lower to mid 40.

18

.LONG TERM /TUESDAY THROUGH FRIDAY/...Some precip from the
aforementioned frontal system cloud linger into Tuesday, mainly
south and east of the Sound. Conditions dry out pretty quickly by
late Tuesday afternoon as another upper level ridge prepares to take
over the weather in the region. Deterministic models differ greatly
on the strength and orientation of the ridge all the while ensemble
solutions are mostly in lockstep advertising persistent dry
conditions, with only a handful of members disagreeing with that.
The dissenters, much like the deterministic models, also disagree on
details with one another. The NBM is favoring an extended dry period
for the majority of the long term and see no reason to disagree with
it at this time.

As one would expect with a prolonged ridge, a warming trend will be
the story for the extended period. Tuesday sees daytime highs akin
to those of Monday with most spots only getting into the lower to
mid 50s...however there look to be some spots in the SW interior
that could push into the upper 50s. Wednesday nudges a little warmer
with highs in the upper 50s to lower 60s. Thursday increases more
with mid to upper 60s and Friday may give the area a warm start to
the weekend as interior locations close in on 70.

&&

.AVIATION...Southwesterly flow aloft as an upper-level trough moves
southward into California. Mostly VFR conditions this afternoon as
cloud cover has largely scattered out, with the exception of CLM.
Skies should remain mostly clear overnight and into tomorrow, with
VFR conditions through the TAF period. Some low stratus may develop
along the Pacific coast and along the Cascade foothills (which may
impact PAE), but the confidence in either of these events occuring
tomorrow morning is fairly low, and will not be included in the TAF
with this update.

Winds remain north/northeasterly across the region at around 8 to 12
kt with occasional gusts to 15 to 20 kt. Winds will ease this
evening to around 5 to 8 kt before returning to 8 to 12 kt again
tomorrow, with directions staying consistent.

KSEA...VFR through the TAF period with mostly clear skies. Northerly
winds 8 to 12 kt (with occasional gusts up to 20 kt) easing tonight
before coming back up tomorrow.

LH

&&

.MARINE...High pressure continues to build well offshore of western
Washington. This high pressure system will slowly creep its way
eastward towards the region this weekend and into the beginning of
next week. As a result, northwesterly winds will slowly build
through the course of this weekend. A Small Craft Advisory will go
into effect tonight for the coastal waters 10-60 NM out. The
pressure gradient looks to sharply increase on Sunday, which will
develop stronger winds through the northern portions of the coastal
waters, as well a solid push through the Strait of Juan de Fuca,
which will likely reach Small Craft Advisory levels, with gusts
reaching up to gale force possible. Winds look to ease into next
week as the high pressure system looks to center itself over the
region.

Seas 6 to 8 ft will gently rise Sunday to 9 to 12 ft, with the
highest waves over the northern coastal waters up towards Vancouver
Island. With the persistent northwesterly winds, waves will become
steep on Sunday with heights 9 to 12 ft with a 9 second period. This
sea state will likely persist into Monday, through could linger as
late as early Tuesday.

LH

&&

.HYDROLOGY...No river flooding is expected through the next seven
days.


&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 11 PM PDT Saturday for Coastal Waters
     From Cape Flattery To James Island 10 To 60 Nm-Coastal
     Waters From James Island To Point Grenville 10 To 60 Nm-
     Coastal Waters From Point Grenville To Cape Shoalwater 10
     To 60 Nm.


&&

$$