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000
FXUS66 KSEW 242244
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
344 PM PDT Wed Apr 24 2024

.SYNOPSIS...Weakening front dissipating over Western Washington
this evening. Next system moving over Western Washington and
stalling Thursday before moving east Thursday night. Cool upper
level trough over the area Friday. Another weather system
arriving Saturday. Upper level trough over the area Sunday into
the middle of next week keeping temperatures below normal into
the first part of May.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...Satellite imagery and
doppler radar show slow moving narrow front on a line from about
Everett to Elma to Astoria. Rain with the front is light with just
a couple hundredths at Everett this afternoon. Cloudy skies
outside of the front. Temperatures much cooler than Tuesday with
lower to mid 50s at 3 pm/22z.

Front will continue to move slowly east eventually dissipating
over the Cascades later this evening. Not much rain left with the
front with less than a tenth of an inch possible. A little break
behind the front late tonight into early Thursday morning with the
next system currently just east of 140W. Cloudy skies overnight
will keep lows in the mid to upper 40s.

Rain ahead of the next system moving into Western Washington
Thursday morning. Weak jet associated with the front digging
south into Oregon Thursday afternoon. This will cause the front
to stretch out, weaken and become stationary over Western
Washington making for a wet late April day. Rain most of the day
will make for little in the way of daytime heating with the high
temperatures only a few degrees above the lows, in the lower to
mid 50s.

As the jet continues to dig south front dissipating over Western
Washington late Thursday night into Friday morning. Daily rainfall
records are on the low side Thursday. For example, the record
rainfall for Seattle is 0.59 inches set in 2020. There is a chance
some daily rainfall records could be broken, not so much from
heavy rain just steady rain all day Thursday. Seattle April
monthly rain total currently at 0.43 inches so there is a chance
Seattle gets more rain Thursday than the previous 24 days in
April. Steady rain giving way to more showery precipitation with
the front dissipating early Friday morning. Lows once again in the
mid to upper 40s.

Cool upper level trough hanging out over the area Friday. Jet well
to the south with little dynamics overhead but cooler air mass
aloft enough to keep showers in the forecast. It will be another
below normal day temperature wise with highs in the mid to upper
50s.

Upper level trough shifting east Friday night with showers coming
to an end. Next system reaching Western Washington during the day
Saturday with rain spreading back over the area. Parent low for
the front in the Northern Gulf of Alaska so this will not be a
strong system with rainfall amounts mostly under a tenth of an
inch. Lows Friday night in the 40s with highs Saturday in the mid
to upper 50s.

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Extended models remaining
consistent in the idea of a cool upper level trough over Western
Washington Sunday and Monday. Snow levels dropping down to near
3000 feet Monday bringing up the possibility of light snow on all
the passes. Some differences in the models show up beginning
Tuesday. There is good agreement that a closed low will form in
the trough Tuesday but the location of this feature is much
different with the GFS taking the low well offshore Wednesday while
the ECMWF has the low much closer to the coast. Even with the
different locations of the upper level low both solutions keep
showers over Western Washington Tuesday and Wednesday along with a
continuation of below normal temperatures. It`s going to be a cool
last week of April for Western Washington. Felton

&&

.AVIATION...W to SW winds aloft with a broad upper-level trough to
the north. A mixed bag of ceilings across the area ranging from VFR
to IFR as scattered showers slowly work their way across the region.
Winds a bit breezy through the central Puget Sound (PWT, SEA, BLI)
but otherwise light south/southwesterly.

Expect CIGs to generally remain low-end VFR to high-end MVFR through
around 06Z Thursday when the next frontal system will usher in more
consistent MVFR to IFR cigs that should persist through most of
tomorrow. Visibility restrictions due to heavy rain is possible,
especially along the coast. Winds will ease tonight, then build back
to more S 8-12kt with gusts up to 20kt possible.

KSEA...Low end VFR to occasional MVFR should persist through early
evening. Solidly MVFR conditions after 06Z Thursday with rain coming
in after 12Z. Limited visibility possible in heavy rain. SW winds 10-
15 kt decreasing to 4-8 kt tonight, then backing to S 8-12 kt with
gusts up to 20kt possible tomorrow.

LH

&&

.MARINE...Scattered showers continue across the coastal waters in
the wake of a dissipated front. A more substantial system will move
through the area waters on Thursday. A more substantial frontal
system will move into the area early tomorrow. Southerly winds will
increase throughout the coastal waters, but the areas with the best
chance to see Small Craft Advisory conditions will be in waters
south of Point Grenville (50-85% probability, especially within 20
NM of shore). As such, a Small Craft Advisory is effect for
Thursday. Additionally, rain will be heavy at times, which will
likely reduce visibilities as low as 1-3NM during the heaviest rain.

Breezy conditions will continue on Friday for the outermost coastal
waters as the low pressure center moves through western Washington.
A weak surface ridge will calm things down on Saturday before another
front moves through the region Sunday. The active pattern looks to
continue into the beginning of next week.

Seas look to remain 4 to 6 feet at about 10 seconds through the rest
of the week and into Saturday. Seas look to rise to 8 to 10 ft
beginning Sunday.

LH

&&

.HYDROLOGY...No river flooding expected in the next 7 days.
Heavier rain over the south slopes of the Olympics Thursday into Thursday
night could push the Skokomish River in Mason county close to
action stage Friday. Felton

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 5 AM to 5 PM PDT Thursday for Coastal
     Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-
     Coastal Waters From Point Grenville To Cape Shoalwater Out
     10 Nm.

&&

$$