329
FXUS66 KSEW 110919
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
219 AM PDT Wed Sep 11 2024

.SYNOPSIS...The first in a series of low pressure systems has
arrived, setting up a more autumnal pattern. Rain continues to
move onshore this morning and will last through much of the day.
Cooler temperatures and cloudy conditions will last throughout the
forecast period with occasional showers. A stronger front may move
through on Monday or Tuesday.


&&

.SHORT TERM /TODAY THROUGH FRIDAY/...Moderate showers are moving
onshore early this morning and will continue to do so throughout
much of the day today. There have been some cloud flashes and
isolated lightning just to the south of our CWA along the coast,
and an embedded thunderstorm cannot be ruled out namely in areas
south of Puget Sound and along the coast. Any thunderstorms that
happen to develop are expected to be pulsey and short lived.
Lightning and gusty winds would be the main associated hazards. That
said, the probabilities are still low. Rainfall amounts through
Thursday morning have gone up slightly, with up to an inch of
precipitation likely in the southern Cascades and a quarter to
half inch throughout much of Puget Sound. Widespread 60 degree
temperatures are expected today, and with the continuation of a
cooler and showery pattern, temperatures like this are expected to
continue through the weekend. Given the nature of the front and
the cooler airmass impacting the area, this front is going to
provide snow to the upper elevations of Mount Rainier, but snow
levels are still going to be higher than locations like Sunrise
and Paradise.

A decrease in shower coverage is likely on Thursday as shortwave
ridging moves in. Temperatures will be only slightly warmer and a
bit closer to 70 degrees, with a similar expectation for Friday.

.LONG TERM /SATURDAY THROUGH TUESDAY/...Ensembles and long range
height anomalies show persistent troughing over the Pacific
Northwest through the middle of next week. A few showers are
likely over the weekend, but won`t be very widespread and perhaps
more confined to the higher elevations. Extending out into the
beginning of next week, there appears to be a more robust frontal
system poised to move in late Monday or Tuesday, dropping in from
the Gulf of Alaska. Timing of its arrival will vary as more
details become clear in subsequent forecast packages.

Kristell


&&

.AVIATION...South to southwest flow aloft this morning will
transition to northerly by late this afternoon as an upper trough
axis shifts onshore then east of the Cascades by this evening. A mix
of VFR and MVFR in scattered showers is expected across Western
Washington this morning. Shower coverage will diminish by late this
afternoon with ceilings lifting to low end VFR for most areas. Light
surface flow and remnant low level moisture favors the redevelopment
of low MVFR or IFR ceilings in stratus tonight into Thursday
morning.

KSEA...A mix of VFR and MVFR ceilings in scattered showers is
expected this morning. Ceilings should be primarily low end VFR 22Z
to 04Z before sinking back to low MVFR or IFR in stratus before
daybreak on Thursday. Light S/SW surface winds will gradually veer
to light northwesterly by late afternoon before backing to light
southerly again tonight.   27


&&

.MARINE...A weak surface trough over the coastal waters will
gradually fill as it shifts onshore this afternoon. Broad surface
ridging centered well offshore then rebuilds through Thursday.
Another weak trough is expected to slide southward from the British
Columbia coast later Friday into Saturday, but remains unlikely to
generate any impacts at this time. 27


&&

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

$$