536
FXUS66 KSEW 122112
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
212 PM PDT Mon Aug 12 2024

.SYNOPSIS...Upper troughing over the region will promote onshore
flow and cooler temperatures through Tuesday. Isolated
thunderstorms will be possible across the North Cascades today and
Tuesday. Brief ridging will build Wednesday into Thursday. An
upper low offshore may bring more widespread precipitation
potential over the weekend.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...Mostly cloudy conditions
across Western Washington this afternoon with continued onshore
flow. There remains a chance for thunderstorms this afternoon over
the North Cascades, with NBM probabilities generally 20-30%,
highest along the Cascade crest in this region. Troughing will
continue through Tuesday, allowing for continued cooler
conditions. High temperatures both today and Tuesday will be in
the mid 60s to low 70s.

Ridging will build briefly into British Columbia Wednesday into
Thursday. This will allow for some additional clearing, especially
Wednesday afternoon. Temperatures will also warm a bit Wednesday
and Thursday, but remain below normal, with highs generally in the
mid 70s for the interior and mid 60s for the coast.

.LONG TERM /FRIDAY THROUGH MONDAY/...Ensembles are consistent in
troughing developing offshore Friday with an upper low lingering
offshore of Washington/Oregon into early next week. Initially,
precipitation potential will generally be confined to the
Cascades on Friday, along with the threat for thunderstorms in
this area. Increasing moisture is expected Saturday and Sunday
with the upper low position and southerly flow aloft, introducing
more widespread shower chances over Western Washington. We will
also have to monitor the potential for convection, particularly
later Saturday into Sunday morning, given the increasing southerly
flow aloft. NBM probabilities at this time for much of Western
Washington are around 15% for thunderstorms during this period.
Showers chances may lingering into Monday with the upper low
offshore. Temperatures will likely remain below normal, mostly in
the mid 60s to mid 70s over the weekend.

JD

&&

.AVIATION...Light and variable flow aloft with an upper level
trough moving over western Washington. Stratus has lifted and
broken up a bit, allowing for ceilings to rise to VFR. VFR
conditions will continue though this evening until stratus will
redevelop and lower through the night into tomorrow morning.
Widespread MVFR ceilings with locally lower conditions possible,
especially along the coast. Expecting a similar evolution tomorrow
to today where ceilings slowly rise back to VFR and become broken
without fully clearing out. Winds remain west to southwesterly 5
to 10 kt, with a few gusts up to 15 kt this afternoon.

KSEA...VFR conditions through this evening, dropping back down to
MVFR early tomorrow morning after 12Z then lifting back up around
18Z Tuesday. Winds continue to remain southwesterly 5 to 10 kt.

LH

&&

.MARINE...Broad high pressure over the East Pacific will continue
onshore flow over the area waters. Diurnally driven pushes down the
Strait of Juan de Fuca will occur each evening with no signs of SCA
level winds for the next few days. Marine stratus and fog each
morning may locally limit visibility at times. The push Thursday
afternoon looks to be the strongest of the week and may get close
to SCA criteria. Seas will remain around 3 to 5 ft through the
rest of the week.

LH

&&

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

$$