FXUS66 KSEW 062310
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
410 PM PDT Sat Jul 6 2024

.SYNOPSIS...Strong high pressure will maintain very hot and dry
conditions across western Washington this weekend through the 
early part of next week. A weak disturbance will bring some cooler
temperatures Wednesday and Thursday with stronger onshore flow. 
However, above normal temperatures and no precipitation is 
expected through the week ahead.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY/...The weather pattern
remains rather persistent for the next few days with strong high
pressure aloft centered offshore. This will maintain very hot
temperatures through the early part of next week, with areas of
Moderate (orange) to Major (red) HeatRisk expected through the
interior portions of western Washington. High temperatures have
climbed well into the 80s to around 90 at this hour, with SeaTac
recording 90 degrees for the first time this year. Overnight lows
will also remain in the lower 60s for areas inland, making for
slow relief from the very hot daytime highs. Still expect Monday
and Tuesday to be the warmest days of the week for most with the
upper ridge axis moving eastward over the region. This will bring
some light onshore influence back to the immediate coast into the
afternoon, but little help for the interior with the thermal low
pressure building overhead and cutting off much in the way of
surface wind. Additionally, expect very warm nights in the
mountains as the subsidence inversion strengthens. See the fire
weather section more details for fire weather concerns.   Cullen

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...Some subtle differences
emerge in the timing of the ridge sliding east and flattening
under the influence of a passing shortwave disturbance, but
overall there is decent agreement that this will be sufficient
enough to take conditions in the interior back down to merely
"warm" or slightly above normal rather than the very hot
conditions from the first half of the week. The increasing 
onshore flow will cool high temperatures Wednesday around 10 
degrees for the interior with mid 70s to mid 80s in the forecast. 
Highs along the coast will also continue to cool, back into the 
60s. The increasing onshore flow will cool morning lows Wednesday 
into the 50s and lower 60s. Very little change through the second
half of the week with temperatures remaining above normal and 
afternoon humidities a little higher owing the onshore influence 
each day.

&&

.AVIATION...Northwest flow aloft as high pressure continues to
build over the Pacific Northwest. VFR conditions will continue to
dominate through the TAF period for all area terminals - the
exception being KHQM, where there is a 40% chance of lower
ceilings from 11z-16z (MVFR/IFR). N/NE winds 8 to 12 knots 
through the region this afternoon, gradually decreasing to 4 to 8
knots this evening. 

KSEA...VFR conditions into Sunday. North winds 8 to 12 knots this
afternoon, lowering to 3 to 6 knots overnight. 

Maz

&&

.MARINE...High pressure still remains offshore, with a thermal
trough lingering over the west coast. North/northwesterly winds 
will maintain over the coastal waters through the weekend for
generally benign marine conditions. 

A surface front will push across the area waters through Wednesday
for increased onshore flow and stronger pushes down the Strait of
Juan De Fuca. Winds will likely be elevated through this period
and look to remain that way through the end of next week.

Coastal seas 4 to 6 feet throughout the weekend, and will
gradually increase to 6 to 8 feet by the end of next week.

Maz

&&

.FIRE WEATHER...As expected, strong high pressure aloft is
continuing to bring very warm and dry conditions to the region.
With the additional factor of instability, the red flag warning
for the Cascades zones (658 and 659) will remain unchanged.
Elsewhere, the primary concern for the lower elevations and
foothills south and east of Puget Sound will be the continued
critical afternoon relative humidity values. For these zones,
there's at least one factor (fuel readiness, instability or winds)
that remains lacking, but given the continued trends there
remains the potential for needing a Red Flag Warning for
additional zones for Monday and Tuesday. Some onshore flow will
bring somewhat higher humidities for the coastal and Olympics
zones Monday, but it could be at late as Wednesday before portions
of the Cascades see notable improvement.

&&

.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 until 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.
&&

$$