970
FXUS66 KSEW 142145
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
245 PM PDT Sun Jul 14 2024

.SYNOPSIS...An upper level ridge will remain in control over
Western Washington through the first half of the for continued
dry conditions and above normal temperatures. Minor day to day
variations in onshore flow will bring the marine layer locally
inland each night and morning. A subtle shortwave entering the
area on Wednesday may bring an increased risk of convection over
the Cascades.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...Broad upper level
ridging remains in place over western Washington. Clear skies
will prevail over the region this afternoon, with some leftover
stratus hugging the coastline. Temperatures this afternoon will
continue to remain above average, with high temps in the interior
reaching the mid to upper 80s, and areas along the coast hovering
in the mid 60s. Onshore flow looks to increase later this evening,
which may pull the marine stratus a little bit further inland than
the previous couple of mornings.

High temperatures on Monday will still remain above average, but
be a touch cooler, in the lower 80s for the interior, and low to
mid 60s for coastal locations, with clear skies prevailing once
again. Temperatures on Tuesday will warm as a thermally induced
trough expands along the coast, with interior temps ranging from
the upper 80s to even low 90s. Areas along the coast will warm
into the mid to upper 70s.

Latest ensemble guidance has been keying in on a negative tilted
trough riding up along the west coast Tuesday night into
Wednesday, pushing a weak shortwave sliding over the region with
southerly flow aloft. This may open the door for elevated
instability which could lead to increased convection over the
Cascades. At this time, model guidance is a bit shaky on
specifics, but it is worth noting for recreation and fire weather
concerns. See the fire weather section for more details.

.LONG TERM /THURSDAY THROUGH SUNDAY/...Upper level ridging looks
to amplify through Saturday, which would result in once again
above average temperatures through the region and minor
fluctuations in onshore flow. There is disagreement heading into
Sunday, where ensembles are showing a weak trough moving onshore
into the beginning of next week. This would mean potentially some
precipitation for the area, but, considering how far out it is,
the most likely scenario is the continuation of warm and dry
conditions for now.

Mazurkiewicz

&&

.AVIATION...Mainly VFR with areas of IFR/LIFR along the coast in
marine stratus. Surface winds generally W-SW 8 to 15 kt, decreasing
overnight. Another marine push early Monday morning will allow low
stratus to spread inland causing MVFR to IFR ceilings, potentially
making it as far east as KSEA/KBFI/KPAE. Conditions will improve for
most inland terminals by 18z-19z, allowing for another mostly clear
day.

KSEA...VFR with S-SW winds 12 kt or less. The marine push early
Monday morning may bring MVFR to IFR ceilings (roughly 40% chance)
as early as 12z-14Z Monday and improving by 18z.

15

&&

.MARINE...High pressure situated offshore will continue into the
early week, allowing for diurnally driven pushes through the Strait
of Juan de Fuca and marine stratus along the coast. Another round of
borderline westerly SCA winds will be driven through the Strait of
Juan de Fuca tonight into the early morning Monday. Weak flow will
allow waves to come down from 6 to 8 feet today to 5 to 6 feet by
Monday afternoon.

Northerly flow will develop by mid-week as a trough deepens
offshore. A surface front will slide northward across the region
late Tuesday into Wednesday with additional fronts crossing area
waters through the remainder of the week. While winds are favored to
stay below criteria for now, seas will rise ta foot or two with the
more active weather pattern to 5 to 7 feet.

15

&&

.FIRE WEATHER...High pressure will persist over the Pacific
Northwest for continued warm and dry conditions, with low level onshore
flow providing excellent relative humidity recoveries each night.
Flow will start to turn southerly Tuesday night into Wednesday,
with an increased potential for convection in the Cascades, with
RH values remaining in the mid to upper 30s during this time.

It is worth noting that especially with a pattern like this, with
our fuels already being so receptive, all it takes is a rogue
lightning strike from a thunderstorm to light these fuels.
Will continue to monitor this threat as latest model guidance is
not latching on to any specifics. For now, will monitor for the
potential of thunderstorms and elevated instability.

Mazurkiewicz

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 5 PM this afternoon to 2 AM PDT Monday
     for Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$