929
FXUS66 KSEW 042204
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
304 PM PDT Thu Jul 4 2024

.SYNOPSIS...Very warm week ahead for western Washington as a ridge
slowly drifts over the area. Temperatures will warm into the 90s
area-wide by Sunday and Monday. The ridge will slowly exit to the
east making for a gradual cooling trend going into middle of next
week.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY/...Overall key messages have
not changed with this forecast update.

* HEAT...Continued warming will lead to hot conditions beginning
  Friday. Temperatures peak for most of the region in the upper 80s
  to upper 90s on Sunday, before beginning to slowly ease into next
  week. A Heat Advisory is in effect for the entire region beginning
  Friday afternoon, ending Sunday evening for the coast, Monday
  evening elsewhere.

* FIRE WEATHER...Increasing dry and unstable conditions for this
  weekend has warranted the issuance of a Fire Weather Watch for
  the Cascades. See the Fire Weather discussion below for details.

Not a cloud in the sky can be spotted on satellite imagery this
afternoon with temperatures in the upper 70s to low 80s through
most of the area, cooler in the mid 60s to mid 70s along the
coast. Water vapor imagery shows the ridge axis offshore, with the
highest heights centered over central California. The ridge will
amplify Friday and Saturday before the ridge axis slowly moves
over the region on Sunday.

High and low temperatures will increase each day. Highs Friday and
Saturday will be similar, in the 80s around and north of Seattle,
low to mid 90s through the Southwest Interior, 70s along the
immediate coast. Sunday looks to be the warmest day across the
region, with widespread 90s, reaching near 100 in locations along
the interior Chehalis valley and the Cascade valleys. Record high
temperatures are comparatively low compared to surrounding days,
so it appears that record highs will potentially be set for the
day (July 7th). Temperatures along the coast will range from the
mid 70s to mid 80s. Low temperatures will rise from the low to mid
50s on Friday morning to the low to mid 60s on Monday morning.
Lows will be locally warmer in the urban heat islands.

HeatRisk values remain Moderate through most of western Washington
through the short term, with the exception of the coast. Sunday sees
the introduction of some isolated areas of Major HeatRisk, most
notably in the urban heat islands and west-facing slopes and valleys
of the Cascades.

.LONG TERM /MONDAY THROUGH THURSDAY/...Ensemble solutions are in
good consensus that the ridge axis will gradually move across the
region, finally moving to the east Tuesday into Wednesday.
Temperatures look to remain very warm on Monday, similar to Sunday
through perhaps a degree or two cooler. A weak push along the coast
will keep conditions cooler there. Increasing onshore flow going
into mid-week will allow temperatures to gradually decrease a few
degrees each day going into mid-week though still remaining above
average.

LH

&&

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

KSEA...Clear. N winds 10-15kt through 03z, easing and becoming NE
to 5 kt thereafter.

33

&&

.MARINE...Light, offshore flow through the weekend with a thermal
trough along the coast. The flow will turn onshore Monday and
Tuesday with stronger westerly pushes down the strait.

33

&&

.FIRE WEATHER...Benign fire weather conditions are expected to
remain for today. However, confidence is high on an amplifying upper-
level ridge settling over the region beginning Friday. 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 falling upon the holiday
weekend. Because of this we`ve issued a fire weather watch for zones
658 and 659. 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 and 652 but won`t be strong enough to completely
limit the threat for the Cascades early next week.

McMillian

&&

.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.

     Fire Weather Watch from Saturday morning through Sunday evening
     for West Slopes of the Central Cascades Generally above
     1500 Feet-West Slopes of the North Cascades Generally above
     1500 Feet.

PZ...None.
&&

$$