054
FXUS66 KSEW 251609
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
909 AM PDT Wed Sep 25 2024

.SYNOPSIS...A weather system will move across the region today,
bringing more widespread rain, breezy winds, and chances of
isolated thunderstorms to western Washington. Another system will
move into the region Thursday evening into Friday, bringing
another round of rain and gusty winds. Conditions will then dry
out over the weekend. Additional, weaker systems may move into
the area early next week.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...Main precip band is along the
coast and will push inland late morning and afternoon. There is a
slight chance of thunderstorms in the interior and Cascades as
well. No major updates this morning. 33

Previous discussion...A fall-like weather system will move across
western Washington today. Radar shows a pre- frontal band of rain
already making its way inland along the coast and pushing into
portions of the Northern Interior early this morning. Expect rain
to continue to make its way inland through the morning and
afternoon hours as the main frontal system moves through the area.
Rain will taper to showers by this evening, with increased
onshore flow in the wake of the front allowing for a convergence
zone to develop across King/Snohomish counties. Southerly winds
will become breezy across the region in the vicinity of the front.
The airmass will also be slightly unstable, so some isolated
thunderstorms will be possible throughout the day. Rainfall
amounts generally look to range from a quarter of an inch to half
an inch across the interior lowlands, half an inch to three
quarters of an inch for the coast, and 1-2 inches for the
mountains. High temperatures will be in the 60s area-wide.

Expect a brief break in the weather on Thursday before the next
system moves in Thursday night into Friday. Rainfall amounts
generally look to trend lighter than that of the system today,
with most areas across the lowlands expected to receive a few
tenths of an inch to a quarter of an inch. Amounts look to be
higher along the North Coast, Olympics, and North Cascades- where
amounts of half an inch to an inch will be possible. This system
looks to bring more widespread breezy southerly winds to the
region, with the highest gusts likely being along the North Coast
and areas north of Everett - where gusts to 35 mph will be
possible. Temperatures will generally trend in the 60s to low 70s
both Thursday and Friday.

.LONG TERM /SATURDAY THROUGH TUESDAY/...Weak upper level troughing
looks to set up over the region over the weekend. With not much
in the way of moisture or forcing, the weekend generally looks to
remain cool and mostly dry. Cannot rule out a few light isolated
showers, however, so will need to continue to monitor how guidance
trends throughout the week. High temperatures generally look to
trend in the 60s, with overnight lows expected to be in the 40s
and 50s. Additional weak disturbances may move across the region
early next week and bring additional chances of showers at times.
14

&&

.AVIATION...Southwest flow aloft will increase into early Wednesday
as a frontal system moves across the area. Mix of flight conditions
continue this morning with the approaching front. Rain continues to
move onshore over the coast. Conditions have deteriorated to
IFR/MVFR along the coast due to rain/mist. These worsening
conditions will continue to spread inland today, as rain increases
across the remaining terminals late this morning and afternoon. The
rain rates will lower visibilities at times to 2-5 miles. In
addition, a convergence zone is also expected to develop over
Snohomish and King counties into Wednesday evening. Increasing
south/southwest surface winds through the day, with gusty conditions
especially along the coast and far north.

KSEA...VFR conditions this morning with gradually lowering ceilings
as the front approaches. Approaching cold front will bring rain
across the terminal area 17-22z with a developing PSCZ to the north
of the terminal into Wednesday evening. Ceilings will lower to MVFR
with this activity, with visibilities also dropping anywhere from 2
to 5 miles with the heavier rain. Southerly surface winds will
continue at the terminal most of the day, with gusts increasing late
morning through afternoon. Currently not expecting a significant
shift to northerly winds with the convergence zone remaining north
this evening (will see southeasterly winds instead). Cullen/HPR

&&

.MARINE...An approaching front will continue to advance across the
coastal waters this morning. Expect breezy southerly winds ahead of
the front to increase, followed by northwest winds behind the front
as it pushes inland. Winds gusts ahead of the front may occasional
gusts around 20-25 kt, but these aren`t expected to be frequent or
widespread enough for an advisory. However, an advisory has been
issued for the outer coastal waters with seas increasing to around 9
to 11 feet through the day today as this system pushes eastward. In
the Strait of Juan de Fuca however, gusts may reach gale
periodically in the east section at times this afternoon, with them
peaking at 33 to 35 kt. Sustained winds are expected to remain at 24
to 28 kt.

The next disturbance will then be quick to follow, with a deeper low
strengthening and curling north toward Haida Gwaii on Thursday.
Expect a more widespread swatch of gusty southeasterly winds ahead
of the front as the cold front sweeps through the coastal waters and
inland, following by a stronger round of west winds through the
Strait of Juan de Fuca. This will bring around a 40% chance of gales
through the Strait as the onshore flow surges through. Meanwhile,
seas over the coastal waters will increase more significantly into
the 13 to 16 ft range (highest over the outer coastal waters) on
Friday. Cullen/HPR

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until midnight PDT tonight for Central U.S.
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
     Strait Of Juan De Fuca.

     Small Craft Advisory until 4 PM PDT this afternoon for Coastal
     Waters From Cape Flattery To James Island 10 To 60 Nm-
     Coastal Waters From James Island To Point Grenville 10 To
     60 Nm-Coastal Waters From Point Grenville To Cape
     Shoalwater 10 To 60 Nm.

&&

$$