482
FXUS66 KSEW 101740
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
1040 AM PDT Wed Jul 10 2024

.SYNOPSIS...An upper level ridge remains over Western Washington
through the weekend with continued low-level onshore flow. Little
change through the week ahead with temperatures remaining above
normal and no rain expected.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...Forecast remains on track
this morning with some shallow marine stratus remaining along the
coast and extending along the lower Chehalis as well as in the
eastern Strait of Juan de Fuca. Temperatures this morning trending
cooler than this time yesterday with the cooling aloft and the
addition of the marine influence. Still some temperatures near 90
in the Cascade foothills today and perhaps even in the eastern
portions of the Seattle area, but looks like the heat advisory is
well on track to expire this afternoon. Remainder of previous
discussion follows.

Little change in the pattern tonight through Friday with the flat
upper level ridge over the area and varying degrees of low level
onshore flow. 500 mb heights remaining in the mid 580 dms. 850 mb
temperatures also remaining fairly consistent in the plus 16C-18C
range. The increased difference in the high temperatures between
the coast and the interior this afternoon will increase the low
level onshore flow tonight. This will bring more marine air into
the interior Thursday for another 5 degrees or so of cooling on
the high temperatures. Highs both Thursday and Friday for the
interior in the mid 70s to mid 80s. With more marine air getting
into the interior both nights lows in the 50s.

A heat advisory is still in place for portions of the interior
until 5 pm this afternoon. With lows dropping into the 50s the
next couple of mornings this will lessen the HeatRisk across the
area.

.LONG TERM /SATURDAY THROUGH TUESDAY/...Models in good agreement
with little change in the pattern for most of the extended period.
Flat upper level ridge remaining over the area through the
weekend with 500 mb heights remaining in the mid 580 dms. In the
lower levels varying degrees of onshore flow through Sunday. Some
of the ensemble solutions have a very weak trough moving through
Monday. The only thing this feature will do, if it comes about,
will be to enhance the marine layer a little Monday morning.
Ensembles in good agreement that the flat ridge will rebound
Tuesday. Highs temperatures for the interior in the mid 70s to
mid 80s. Along the coast highs in the 60s and lower 70s. Lows
mostly in the 50s each morning. Felton

&&

.AVIATION...Upper ridge axis well east of the area with southwest
flow aloft. VFR in place for most TAF sites and expected to remain
that way for much of the TAF period. The main exception will HQM
where IFR conditions persist due to marine stratus. These low cigs
will linger into the mid to late afternoon before gradually mixing
out. This break will only be brief however as stratus are expected
to return tonight, lowering cigs once more. With this latter push,
marine stratus may get as far inland as PWT, lowing their cigs down
into MVFR to IFR conditions overnight as well.

KSEA...VFR throughout the TAF period. SW surface winds in place for
the remainder of the morning generally ranging 4 to 8 kts. Will see
a shift to more westerly flow by mid afternoon. Transition to NW
winds expected a little later, closer to 00Z and speeds increasing 8
to 12 kts. Overnight, winds ease to around 5 kts with a shift to
slight northeasterly.

McMillian/18

&&

.MARINE...Surface ridge over the NE Pacific will strengthen
just off the coastal waters through the week. A thermal trough is
shifting east of the Cascades, resulting in increased onshore flow.
Shallow marine stratus still clinging to the coast, however outer
waters are seeing some clearing. Forecast still looks on track for
Gales in the central and eastern Strait, so inherited headline will
continue unaltered. Persistent onshore flow will remain in place
into the weekend with diurnally driven westerly pushes through the
strait possibly accompanied with additional headlines.

Seas generally 4 to 6 ft today before increasing to 6 to 8 ft
Thursday and nearing 10 ft by Friday for the outer coastal waters.

McMillian/18


&&

.FIRE WEATHER...The red flag warning for the Cascades ended late
last night. Increasing low level onshore flow will help with
humidity recoveries in the early morning hours and keep late
afternoon relative humidity values from dropping as low as they
have the last few days. Even though the current weather conditions
do not meet red flag criteria, this last week of hot dry weather
dried out the area significantly and the fire danger across
Western Washington is much higher than it was at the start of the
month.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory until 5 PM PDT this afternoon for Bellevue and
     Vicinity-Bremerton and Vicinity-East Puget Sound Lowlands-
     Everett and Vicinity-Hood Canal Area-Seattle and Vicinity-
     Tacoma Area-West Slopes North Cascades and Passes-West
     Slopes North Central Cascades and Passes-West Slopes South
     Central Cascades and Passes.

PZ...Small Craft Advisory until 5 PM PDT this afternoon for Central
     U.S. Waters Strait Of Juan De Fuca-East Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Gale Warning from 5 PM this afternoon to 5 AM PDT Thursday for
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance
     U.S. Waters Strait Of Juan De Fuca.

&&

$$