FXUS66 KSEW 252218
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
318 PM PDT Sun Aug 25 2024

.SYNOPSIS...Weak high pressure returns to the area today before
another system moves in from the north on Monday into Tuesday.
High pressure reestablishes itself over the region Wednesday
onward for more seasonable temperatures and drier conditions. Low
level flow will be turning offshore Thursday into next weekend.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...Lots more sunshine is
prevailing this afternoon as clouds have widely scattered.
Temperatures are in the 60s and low 70s this afternoon. Shortwave
ridging will keep things dry for the rest of today and much of
tomorrow ahead of the next system that will move in from the north
Monday evening. Winds will begin to pick up from the WSW on Monday
afternoon, with the breeziest locations being throughout Puget
Sound, the Pacific coast and along the Strait of Juan de Fuca.
Area wide winds will increase to 10 to 15 miles per hour, gusting
to 20 to 25 miles per hour by early Tuesday morning, lasting into
the afternoon.

Rainfall on Monday night into Tuesday will be light for most in
Puget Sound, with only a few hundredths to a tenth of an inch of
rain likely. Slightly higher amounts of up to a quarter to half
inch of rain are possible in the central and northern Cascades.
This activity will taper by Tuesday afternoon and high pressure
will resume come Wednesday. Temperatures will be slower to rebound
on Wednesday in the wake of the previous system, but high
pressure is trending to remain over the area for the rest of the
late week period, offering a better chance at seasonal to slightly
above average temperatures by the end of the week.

.LONG TERM /THURSDAY THROUGH SUNDAY/...High temperatures will
become steadily warmer on Thursday and climb into the upper 70s
and low 80s for much of western Washington. This can be attributed
partly due to light offshore flow setting in by the late morning
hours on Thursday as thermal troughing sets up along the Oregon
and Washington coasts. Relative humidity values through the
Cascade gaps and through portions of the southwest interior will
decrease into the 30 percent range, but in the absence of stronger
flow, will pose less fire weather concerns. This offshore flow
pattern will repeat into the weekend, and will continue to bring
the relative humidity values in the Cascades down as it continues.
Recoveries overnight will be in the 60 to 80 percent range,
minimizing concerns posed by the low points in the afternoons. The
warmest day of the upcoming forecast period looks to be Saturday,
with widespread highs in the low to mid 80s.

Ensemble and deterministic forecasts are attempting to show a
cut-off low form off the northern California coast by next Sunday,
meandering onshore and potentially picking up some monsoonal
moisture to return to the PNW with. Right now, nothing is certain
at this lead time, but should it remain a persistent feature in
subsequent model runs, could be the next point of interest once
the upper level ridge begins to move out of the area. Wouldn't put
much stock in this outcome for now, but something to watch.

Kristell

&&

.AVIATION...Weak high pressure aloft remains across Western
Washington, which is maintaining northerly flow at the upper levels.
Low clouds have scattered across much of the region, maintaining
mostly VFR conditions. Low level winds remain mostly southerly this
morning, switching to northerly (and west near the Strait) by
evening. Low clouds likely return overnight for some spots, but
coverage should be less widespread tonight as the air mass dries a
bit. The next front begins to approach late in the day Monday, with
increasing clouds through the afternoon.

KSEA...Mostly VFR through the day with just some scattered clouds.
Otherwise, southerly surface winds veering to northerly late this
afternoon but remaining light. Some lower clouds may reform late
tonight after 11z with around a 25% chance for low MVFR ceilings
around daybreak, but scattering quickly later Monday morning.
Cullen


&&

.MARINE...High pressure remains across the waters through
tonight and into early Monday. However, this will be a short break
with the next frontal system reaching the waters late Monday before
it pushes onshore Tuesday. Stronger winds behind the front will
likely bring winds to 25 kt starting late Monday night over portions
of the coastal waters and then the Strait of Juan de Fuca into
Tuesday. This will build seas closer to 7 to 8 feet, especially over
the outer coastal waters, with choppy conditions resulting from the
persistent northerly winds. A more typical late summer pattern
develops for the second half of the week with diurnally driven winds
peaking during the afternoon and evening hours and shorter period
seas over the coastal waters.  Cullen


&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&

$$