909
FXUS66 KSEW 251043
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
343 AM PDT Sat May 25 2024

.SYNOPSIS...Upper level trough moving through Western Washington
today followed by a weak front for Sunday. Upper level trough
offshore with upper level ridge well to the east Memorial Day.
System spinning out of the trough moving through Tuesday with the
trough moving over the area Wednesday into Thursday. Upper level
ridge building into British Columbia Thursday night into Friday.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...Satellite imagery shows
cloudy skies over Western Washington early this morning. Doppler
radar shows convergence zone near the East Entrance to the Strait
of Juan de Fuca with isolated showers elsewhere. With the cloud
cover temperatures were in a narrow range at 3 am/10z, a couple of
degrees either side of 50.

Upper level trough moving through the area today keeping showers
in the forecast with the higher pops in the morning. Convergence
zone will slowly drift south and east with the northwesterly flow
aloft over the area. The convergence zone will dissipate this
afternoon. Plenty of cloud cover through the day will keep high
temperatures mostly in the 50s.

Weak upper level ridge moving through Western Washington tonight
with shower activity decreasing especially over the lowlands. Low
level onshore flow keeping skies mostly cloudy. Lows in the mid to
upper 40s.

Weak system moving out of the large upper level trough in the
Gulf of Alaska moving by mainly to the north Sunday. System close
enough to have showers in the forecast for the coast and Northwest
Interior and at least a chance of showers elsewhere. Cloud cover
over Western Washington combined with the shower activity will
result in another cool day for this time of year. Highs in the 50s
and lower 60s.

Upper level ridge building well east of the area Sunday night into
Memorial Day with the large upper level trough offshore slowly
digging south. Ridge too far east to completely protect the area
from any shower activity with a chance of showers west of a line
from about Hoquiam to Mount Baker. Temperatures aloft warming
slightly and with a little less cloud cover highs getting into the
60s.

.LONG TERM /TUESDAY THROUGH FRIDAY/...Extended models in good
agreement with another frontal system moving into Western
Washington Tuesday with the trailing upper level trough arriving
Wednesday. Trough moving east of the area Thursday but not fast
enough to keep showers out of the forecast. Upper level ridge
nosing into British Columbia Thursday night into Friday. Some
differences in the models start showing up Thursday night with the
ECMWF much stronger with the upper level ridge versus the GFS.
Both models pretty dry Friday with pops mostly in the slight
chance category. Temperatures remaining unseasonable cool Tuesday
through Thursday with highs in the mid 50s to lower 60s. A little
warmer Friday with highs in the lower to mid 60s. Felton



&&

AVIATION...A weak cold front continues to advance east of the
region with lingering PSCZ activity across the northern portions of
Puget Sound early this morning. Expect the air mass to remain moist
with widespread low MVFR to IFR conditions expected this morning.
Little change through midday, but the PSCZ should weaken and
ceilings gradually begin to rise through the afternoon for many
locations.

KSEA...Lower MVFR conditions expected early this morning with
occasional light rain. Main PSCZ activity should remain north of
KSEA and KBFI to keep southerly surface winds at both terminals this
morning. Gusty winds increase this afternoon to 20 kt. Otherwise
expect ceilings to trend toward VFR by 22z before setting back into
MVFR by 12z Sun.

&&

.MARINE...Weak cold front will continue to slide east with breezy
northwest winds over the coastal waters and west winds through the
Strait of Juan de Fuca this morning. Expect winds to ease over the
coastal waters mostly by daybreak or mid-morning, but seas will also
remain steep through this time. The advisories for the coastal
waters will run through the morning. Meanwhile, west winds through
the Strait will again increase with another round of advisory
strength westerlies this evening. A stronger front will approach
early Sunday, with yet another disturbance early next week. Both of
these will increase the potential for advisory strength winds over
portions of the waters as well as lead to a return of steep seas
over the coastal waters.

&&

&&

.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 8 AM PDT this morning for Coastal
     Waters From Cape Flattery To James Island Out 10 Nm-Coastal
     Waters From James Island To Point Grenville Out 10 Nm-
     Coastal Waters From Point Grenville To Cape Shoalwater Out
     10 Nm.

     Small Craft Advisory until 11 AM PDT this morning 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.

&&

$$