198
FXUS66 KSEW 280920
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
220 AM PDT Tue May 28 2024

.SYNOPSIS...A cold front will cross western Washington today with
a quick round of widespread rainfall, which will decrease into
showers through the day Wednesday. A shortwave ridge and surface
high to our south will bring warmer and drier conditions. A warm
front will slowly lift across the Pacific Northwest late Saturday
into Sunday with another series of weak frontal systems looking to
move across the region into early next week.

&&

.SHORT TERM /TODAY THROUGH THURSDAY/...Rain continues to move
towards the coast this morning on radar in association with an
incoming cold/occluded front. This will bring a brief period of
stratiform rain to most of the area as the front passes across
western Washington today. High temperatures on the cool side in
the mid to upper 50s, some 10 degrees below normal for late May.

This front continues to skirt eastward into Wednesday morning
with rain transitioning to showers, favoring the typical Puget
Sound Convergence Zone-affected areas in central Snohomish
County. HREF member consensus redevelops this PSCZ along the King
and Snohomish County line early Wednesday afternoon. Low-topped
convection is possible once again thanks to the upper-level trough
axis moving overhead with anomalously cold 500 mb heights around
-25C. The best chance for any thunder will be in the convergence
 zone over this area, though the probability for thunder only tops
 out around 20% with maximum SB CAPE only at 200 J/kg. Primary
 hazards with any isolated thunderstorms that do form will be
 small hail and brief gusty winds. High temperatures Wednesday
 once again in the upper 50s to near 60 into the Southwest
 Interior.

Shortwave ridging builds inland Thursday with surface high
pressure centered well off the northern California coast. Drier
conditions return Thursday with highs warming into the low to mid
60s.

.LONG TERM /FRIDAY THROUGH MONDAY/...High pressure keeps dry and
mild conditions in place Friday with highs finally returning to
seasonal normals. The ridge axis shifts to our east through the
weekend as a deep vertically-stacked low forms over the Gulf of
Alaska, ejecting a series of shortwaves northeastward across the
Pacific Northwest into early next week. Long range ensemble
consensus keeps wet pattern in place into early next week with the
several inches of QPF possible across the Olympics and Cascades
Sunday and Monday (60% chance for 2 inches or more of liquid
precipitation accumulation). High temperatures look to favor the
mid to upper 60s into early next week as well.

Davis

&&

.AVIATION...Southwesterly flow aloft continues today as
a weakening front moves onshore ahead of an upper trough over the
offshore waters. Post-frontal onshore flow will lead to the
development of a convergence zone over north and central Puget Sound
this afternoon and evening. Ceilings will lower to MVFR 12z-15z this
morning in light rain. Ceilings will lift back up to VFR again
behind the front 21z-00z except in a convergence zone near KPAE
where ceilings will remain MVFR.

KSEA...Ceilings will lower to MVFR 12z-15z then lift back up to VFR
again behind the front 21z-00z. Surface winds becoming southerly 4
to 8 knots rising to southwesterly 7 to 12 knots this afternoon.

27

&&

.MARINE...A weak front will move onshore late this morning with
increasing onshore flow in its wake. This will lead to small craft
advisory westerlies in the central/east strait this afternoon and
evening. Broad surface ridging builds over the coastal and offshore
waters on Wednesday with a likely repeat of afternoon and evening
small craft advisory westerlies in the strait. The combination of
surface ridging offshore and lower pressure inland will maintain
onshore flow through the remainder of the week. The onshore flow
will weaken somewhat by Friday as high pressure aloft moves over the
area. Another weak front is expected to arrive on Saturday.

27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 2 PM this afternoon to 2 AM PDT
     Wednesday for Central U.S. Waters Strait Of Juan De Fuca-
     East Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$