573
FXUS66 KSEW 041555
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
855 AM PDT Thu Jul 4 2024

.UPDATE...Pleasant start to the 4th of July today with clear skies
and temperatures in the low to mid 60s across western Washington
as of 845 AM. High temperatures are still on track today to reach
the upper 70s to mid 80s through the interior, mid 60s to mid 70s
along the coast. No changes to the forecast, see below for
updates for the aviation section.

LH

&&

.SYNOPSIS...Very warm week ahead for Western Washington. Upper
level ridge offshore today will slowly drift east over the weekend
ending up over Western Washington Sunday and Monday. The center of
the ridge will move off to the east Tuesday and Wednesday. High
temperatures warming into the weekend peaking Sunday and Monday.
Gradual cool down beginning Tuesday with the ridge moving east.

&&

.SHORT TERM /TODAY THROUGH SATURDAY/...Little change in the
forecast this morning. Heat advisory will remain in effect for the
interior Friday afternoon through Monday evening and Friday
afternoon through Sunday evening for the coast.

Satellite imagery shows clear skies over most of the area with a
small patch of stratus and fog near Grays Harbor. Temperatures at
3 am/10z were in the 50s and lower 60s.

Upper level ridge over Western Washington today with the ridge
axis offshore near 130W. Light flow in the lower levels turning
northerly this afternoon. Stratus and fog near Grays Harbor will
dissipate by mid morning. Clear skies over the remainder of the
area. Temperatures aloft warming today with 850 mb temperatures
rising from plus 10C to 14C to plus 16C to 18C by 00z Friday.
Northerly afternoon breeze will cut a couple of degrees off the
high temperatures near the water. Highs mid 70s to mid 80s inland
and lower to mid 70s coast.

Little change in the pattern tonight and Friday with the ridge
axis remaining near 130W with northerly flow in the lower levels
across the area. Ridge building a little resulting in slightly
warmer temperatures aloft Friday afternoon, 850 mb temperatures in
the plus 20c to 22C range. Lows tonight in the 50s. Highs Friday
warmer with 80s and lower 90s inland and mid 70s to mid 80s coast.

Thermally induced surface trough along the Oregon coast Friday
will try and move north Friday night into Saturday with the trough
ending up over the Western Washington interior Saturday afternoon.
Even with the surface thermal trough low level winds above the
ground to 850 mb remain northwesterly. Without a good switch to
offshore flow highs Saturday similar to Friday, 80s and lower 90s
inland and mid 70s to mid 80s coast. Lows Friday night in the mid
50s to lower 60s.

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Extended models in good
agreement with the upper level ridge drifting towards the coast
Sunday. Ridge axis along the coast Monday moving inland Monday
night and east of the Cascades Tuesday and Wednesday. Highs
peaking along the coast Sunday, upper 70s to mid 80s, and over
the interior Sunday and Monday, mid 80s to upper 90s. Weak
onshore flow developing along the coast Monday as the ridge axis
moves into the interior with the weak onshore flow spreading to
the interior Tuesday as the ridge axis moves east of the Cascades.
Even with the ridge axis to the east temperatures aloft will only
cool slightly Tuesday and Wednesday. With the onshore flow being
rather shallow Tuesday high temperatures will only cool a couple
of degrees in the interior, 80s to mid 90s. A little bit stronger
onshore flow Wednesday lowering high temperatures a little more,
upper 70s to near 90. Highs along the coast Monday and Tuesday in
the upper 60s to mid 70s, Wednesday mid 60s to lower 70s. Lows
Sunday night for the interior in the upper 50s to mid 60s and mid
50s to lower 60s Monday and Tuesday night. Lows along the coast in
the mid to upper 50s.

Felton

&&

.AVIATION...High pressure and offshore flow will lead to a dry
and stable air mass across western WA with VFR conditions.

KSEA...Clear with N winds, increasing to 10-15kt 21-03z.

33


&&

.MARINE...Strong high pressure remains offshore through the
week, which will continue to dominate the weather pattern. A
building thermal trough will bring breezy northerly winds to the
coastal waters and Puget Sound. These will peak each afternoon and
evening, and while mostly well below advisory criteria. There`s some
potential that winds over the outer coastal waters do occasionally
get into the 20-25 kt range, but confidence is low. Meanwhile, the
persistent northerly winds will maintain rather steep seas over the
coastal waters with seas generally 5 to 7 feet at around 8 or 9
seconds for the remainder of the week.

12

&&

.FIRE WEATHER...Benign fire weather conditions are expected to
remain through today. However, confidence is high on an
amplifying upper-level ridge settling over the region beginning
Friday. Not only will dry conditions persist, but hot weather is
in the forecast thanks to easterly flow created by a developing
thermal pressure trough along the coast. The heat is expected to
peak over the weekend with the hottest temperatures likely on
Sunday. Critical RH values are trending widespread over the
Cascades with isolated areas within the Olympic Mountain valleys
during this time. The hot and dry setting will be enough to
maintain elevated fire weather conditions especially with fuels
expected to dry out rapidly during this heat stretch. The next
notable push of onshore flow will arrive Sunday night into Monday.
It`ll bring decent RH recoveries to fire zones such as 650 but
won`t be strong enough to completely limit the threat for the
Cascades early next week.

McMillian/18

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory from noon Friday to 10 PM PDT Monday for Admiralty
     Inlet Area-Bellevue and Vicinity-Bremerton and Vicinity-
     East Puget Sound Lowlands-Eastern Strait of Juan de Fuca-
     Everett and Vicinity-Hood Canal Area-Lower Chehalis Valley
     Area-Olympics-San Juan County-Seattle and Vicinity-
     Southwest Interior-Tacoma Area-West Slopes North Cascades
     and Passes-West Slopes North Central Cascades and Passes-
     West Slopes South Central Cascades and Passes-Western
     Skagit County-Western Whatcom County.

     Heat Advisory from noon Friday to 10 PM PDT Sunday for Central
     Coast-North Coast-Western Strait of Juan De Fuca.

PZ...None.
&&

$$