Allen, Washington Weather Forecast Discussion

608
FXUS66 KSEW 302213
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
313 PM PDT Tue Sep 30 2025
.SYNOPSIS...A frontal system will move through the area tonight
bringing rain and locally windy conditions. An unstable air mass
behind the front will lead to showers and isolated thunderstorms on
Wednesday. A weakening trough over the region will keep conditions
unsettled into Friday. A trend toward drier weather will begin over
the weekend as a ridge of high pressure aloft builds offshore.
&&
.SHORT TERM /TONIGHT THROUGH FRIDAY/...A negatively tilted upper
trough offshore is slowing the eastward progression of an incoming
frontal system, but rain is still on track to reach coastal areas
this afternoon then spread across the interior this evening. A sub
980 millibar low west of Vancouver Island`s north end will tighten
southeasterly gradients for windy conditions in favored spots along
the coast and interior areas from Admiralty Inlet northward. A
somewhat unstable air mass will follow the front on Wednesday for
showers and a chance of thunderstorms across much of the area. The
vertically stacked nature of the trough wobbling offshore will lead
to a gradual decrease in intensity of winds Wednesday night into
Thursday. Conditions will remain unsettled Thursday into early
Friday as the upper trough gradually fills and shifts eastward.
Temperatures through the short term period will remain near or a
little below normal.
.LONG TERM /SATURDAY THROUGH TUESDAY/...The synoptic pattern
begins to amplify over the weekend as broad upper troughing takes up
residence over the interior West while upper ridging builds over the
northeast Pacific. A system may clip the area early in the weekend
for a chance of showers on Saturday, but the upper ridging offshore
is expected to become the more dominant player early next week for a
shift toward drier conditions and slightly above average
temperatures. Forecast uncertainty increases quite a bit by Tuesday
as models begin to wrestle with the prospect of potential Rex Block
pattern setting up over the western third of the country. 27
&&
.AVIATION...Southwest flow aloft with a vigorous frontal system
moving onshore this afternoon. Rain along the coast will spread to
the interior between 00-01Z. Increasing mid and high clouds this
afternoon with VFR conditions and ceilings 5-6 kft this evening. MFR
conditions are possible with heavier or persistent showers,
otherwise VFR conditions will persist through the night for most
locations, except for the coast, and KPWT where MVFR and possibly
IFR ceilings will develop by morning.Increasing southerly winds with
fairly widespread gusts to 25 kt - strongest along the coast and
northern areas from KNUW northward. Winds will remain southerly and
gusty through Wednesday.
KSEA...VFR ceilings at the terminal through the evening, with rain
reaching the terminal 00-01Z. Ceilings are expected to remain VFR,
though cant rule out a period of MVFR conditions with heavier
rainfall. Southerly winds 7-9kt will become 10-20 kt over the next
few hours with gusts to 25 kt be possible through the night.
&&
.MARINE...A strong frontal system will move across the area waters
today into Wednesday, bringing southerly gale force winds to the
Coastal Waters, Eastern Strait of Juan de Fuca, and portions of the
Northern Inland Waters. Elsewhere, small craft strength winds are
expected. Winds will remain elevated through Wednesday as a strong
low pressure system loiters offshore. Seas will rapidly build
towards 15-17 ft today and to 16-19 ft by Wednesday.
The low pressure system offshore will then weaken on Thursday and
push inland on Friday, allowing for winds to decrease across the
area waters. Seas will gradually subside to below 10 ft through the
day on Thursday and down to 5-7 ft by Friday. Additional weak
systems may move through the area waters over the weekend, however
expect high pressure to build back over the northeastern Pacific by
the end of the week.
14/Cook
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Wind Advisory until 5 AM PDT Wednesday for Island County-
     Lowlands of Western Whatcom County-Port Townsend Area-San
     Juan County.
High Surf Advisory until 5 AM PDT Thursday for Grays Harbor
     County Coast-Northern Washington Coast.
Wind Advisory until 8 PM PDT this evening for Grays Harbor
     County Coast-Northern Washington Coast.
PZ...Small Craft Advisory until 5 PM PDT Wednesday for Admiralty
     Inlet-Central U.S. Waters Strait Of Juan De Fuca-Grays
     Harbor Bar-West Entrance U.S. Waters Strait Of Juan De Fuca.
Gale Warning until 5 PM PDT Wednesday 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-East Entrance U.S. Waters Strait Of
     Juan De Fuca-Northern Inland Waters Including The San Juan
     Islands.
Small Craft Advisory until 5 AM PDT Wednesday for Puget Sound
     and Hood Canal.
&&
$$

NWS SEW Office Area Forecast Discussion