463
FXUS66 KSEW 052147
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
247 PM PDT Fri Jul 5 2024

.SYNOPSIS...Very warm temperatures into next week for Western
Washington as an upper level ridge slowly drifts over the area.
Temperatures will peak Sunday through Tuesday with highs over the
interior in the mid 80s to near 100. The ridge will slowly exit to
the east making for a gradual cooling trend in the middle of next
week.

Key Messages:

* HEAT...Continued warming will lead to hot conditions into next
  week. Temperatures will peak Monday and into Tuesday for the
  interior in the upper 80s to near 100. Highs will be cooler
  along the coast. A Heat Advisory is in effect for the entire
  region, ending Sunday evening for the coast, and Tuesday
  evening elsewhere.

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

&&

.SHORT TERM /TONIGHT THROUGH MONDAY/...Dry, clear weather today as
an upper ridge builds further offshore of western Washington.
Temperatures already range in the 80s for most areas with a few
low 90s observed in the Cascade Valleys, as well as towards the
Chehalis Valley.

The upper ridge will continue to build over the Pacific Northwest
through the weekend and into Monday with hot temperatures and dry
conditions. Temperatures will generally increase a few degrees
Saturday and again on Sunday. Highs both days will be in the 80s
to mid 90s, with the hottest temperatures generally King County
southward, in the Chehalis Valley, and into the slopes of the
Cascades and Olympics. In addition, overnight temperatures will
remain elevated, with little overnight relief, with lows in the
upper 50s to mid 60s. Temperatures will be slightly cooler along
the immediate coast this weekend, with highs in the upper 70s to
low 80s, although a sharp gradient will be likely moving inland.

The ridge axis will move over western Washington Monday into early
next week, with likely the warmest days for the interior Monday
and Tuesday. Highs Monday will range in the mid 80s to 90s,
although perhaps a few 100 degree marks will be possible in the
Cascade Valleys as well as Lewis and Mason Counties. Overnight
temperatures will continued to remain elevated as well, although
cooler temperatures are expected along the coast due to slight
increase in onshore flow. HeatRisk will be widespread Moderate to
areas of Major through early next week, with heat impacting most
individuals sensitive to heat, especially though without effective
cooling or adequate hydration. Make sure to stay hydrated during
this period.

.LONG TERM /TUESDAY THROUGH FRIDAY/...The ridge axis generally
remains over western Washington on Tuesday, although another
slight increase in onshore flow is expected for the coast. Hot
conditions will continue, especially for the interior, with the
Heat Advisory extended through Tuesday for interior areas.
Ensembles suggest the ridge axis slowly slides east on Wednesday
as a weak shortwave slides north of the area into Thursday.
However, continued ridging influence will lead to well above
normal temperatures, despite an increase in onshore flow. NBM
suggests highs remain in the 80s to near 90 for the interior,
with further cooling into Thursday. Above normal temperatures and
dry weather likely to continue late next week. JD

&&

.AVIATION...Northwesterly flow aloft as high pressure amplifies
over the west. Dry and stable airmass over the region will
continue to lead to VFR conditions at all sites throughout the TAF
period.

KSEA...VFR persisting thru the TAF period. North winds this
afternoon 8 to 12 knots, turning more NE this evening and
decreasing around 4 to 8 knots.

Maz

&&

.MARINE...Expanding thermal trough along the trough will give way
to periods of light offshore flow throughout the weekend. Recent
guidance suggests flow turning slightly more onshore Monday night
into Tuesday, with stronger pushes down the Strait of Juan De
Fuca likely into midweek.

Coastal seas generally 4 to 6 feet into the weekend and through
early next week.

Maz

&&

.FIRE WEATHER...All remains consistent in regards to the
amplification of a stout upper-level ridge over the PNW. Hot
temperatures, dry conditions, and slight instability all falling
upon the holiday weekend has lead to the issuance of a fire
weather watch beginning Saturday afternoon for Cascade zones 658
and 659 Fortunately, there`s no wind to combat with as a thermal
trough remains far to the south over S OR. However, this prolonged
heat event will dry out fuels rapidly. Critical RH values are
likely over the Cascades with isolated areas within the Olympic
Mountain valleys over the weekend. Model trends continue to push
back the improving fire weather conditions into now Tuesday-
Wednesday. Decent RH recoveries won`t arrive to the Olympic and
coastal zones until then, however, the interior may not feel
relief until late next week.

McMillian

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory until 10 PM PDT Tuesday 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 until 10 PM PDT Sunday for Central Coast-North
     Coast-Western Strait of Juan De Fuca.

     Red Flag Warning from 11 AM Saturday to 11 PM PDT Tuesday for
     West Slopes of the Central Cascades Generally above 1500
     Feet-West Slopes of the North Cascades Generally above 1500
     Feet.

PZ...None.
&&

$$