400
FXUS66 KSEW 141632
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
932 AM PDT Wed May 14 2025

.UPDATE...Weak convergence zone activity is persisting over the
Puget Sound region this morning. Showers are drippy at best so
rainfall amounts won`t lead to a washout. Conditions are to
trend drier today as cloud coverage remains. Highs will top out
into the mid 50s to lower 60s this afternoon. The previous
discussion remains below along with an updated marine/aviation
section:


&&


.SYNOPSIS...
A passing disturbance will bring stronger onshore flow and
additional showers across the region today. Transient high
pressure builds late Wednesday through Thursday, but the next
frontal system quickly follows. An unsettled weather pattern
will remain in place across the Pacific Northwest this weekend
through early next week, maintaining widespread clouds and rain
showers.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...
Widespread low clouds across the region this morning with some
light rain showers evident in data from NWS radar this morning.
With the dominant upper trough remaining over the Great Basin,
expect stronger onshore flow to again develop later this
morning, aided by a shortwave dropping through southwestern
British Columbia. Expect increased shower activity this morning
near and east of northern Puget Sound, extending eastward
through the Cascades. A Puget Sound Convergence Zone is likely
to develop this afternoon and evening, bringing an additional
focus for shower activity across central Puget Sound eastward
into the Cascades. That said, QPF remains rather modest.

Expect some drying out to occur late this evening through early
Thursday (outside of the previously mentioned PSCZ) as heights
rises a bit with a transient upper level ridge in between the
main weather features. That said, this will be a short-lived
break, as the next frontal system will approach the coastline by
early Thursday and bring yet another round of increased rain
activity. This will knock a few degrees off of the daytime high
temperatures, with the lowlands topping out in the mid 50s to
lower 60s.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
The long term period looks to feature an extended unsettled
pattern, with an upper trough developing across the Pacific
Northwest. There remains broad support in the ensemble guidance
for this outcome, with fairly solid cloud cover and several
rounds of showers. That said, the amounts aren`t too impressive
in any single time period, but the Friday night/Saturday period
might be the wettest time period of the week ahead. The region
will remain in a rather zonal pattern for the start of next week
which will continue shower chances. Temperatures generally in
the lower 60s through the interior lowlands for the start of
next week.

&&


.AVIATION...Northwest flow aloft continues across Western Washington
today as an upper level trough moving across British Columbia
enhances low level onshore flow across the region. This is producing
convergence across the interior lowlands with low MVFR or IFR
ceilings and scattered showers. Showers will diminish toward
afternoon, but ceilings will be slow to improve. Ceilings will lift
to low end VFR most areas after around 22Z. A gradual deterioration
back to MVFR is expected after 06Z this evening.

KSEA...Low MVFR or tempo IFR ceilings expected into midday with a
convergence zone just north of the terminal. Improvement will be
gradual at best with ceilings lifting to low end VFR by around 23Z.
Ceilings will fall back to 020-030 after 06Z tonight.  Surface winds
S/SW 8 to 13 knots this morning will shift W/SW this afternoon as
the convergence zone dissipates just north of the terminal 22Z-00Z.
Winds may become variable for a period around 00Z before returning
to a predominant southerly direction overnight tonight.  27

&&

.MARINE...Surface high pressure over the coastal and offshore waters
will weaken late Thursday as a frontal system approaches the area.
This front will weaken as it moves onshore on Friday. Surface
ridging will rebuild offshore on Saturday then shift into the
coastal waters early next week.

Seas will generally remain under 10 feet through the weekend, but
may approach 10 feet early next week as a swell train generated by a
trough over the northern Gulf of Alaska arrives.  27


&&

.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be included as needed.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 11 PM PDT this evening for Central
     U.S. Waters Strait Of Juan De Fuca-East Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 5 PM PDT this afternoon for Coastal
     Waters From Cape Flattery To James Island 10 To 60 Nm-
     Coastal Waters From Cape Flattery To James Island Out 10 Nm-
     Coastal Waters From James Island To Point Grenville 10 To
     60 Nm-Coastal Waters From James Island To Point Grenville
     Out 10 Nm-Coastal Waters From Point Grenville To Cape
     Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville
     To Cape Shoalwater Out 10 Nm.

&&

$$