Bainbridge Island, Washington Weather Forecast Discussion

524
FXUS66 KSEW 011001
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
259 AM PDT Wed Oct 1 2025
.SYNOPSIS...An unstable air mass associated with upper level low
pressure off the coast will lead to showers and isolated
thunderstorms today. 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 /TODAY THROUGH FRIDAY/...Current IR satellite loop shows
an upper level low out over the Pacific waters well due west of
Vancouver Island this morning. This feature will continue to be the
driving force for W WA weather again today and for the entirety of
the short term. Latest radar continues to show post-frontal showers
associated with this feature over portions of the CWA. Although
lightning strikes have occurred...mainly closer to the parent upper
low and along the coast of the aforementioned Vancouver Island, no
strikes have been detected over any portion of W WA overnight nor
early this morning. Not sure how long that will hold however as
conditions become increasingly unstable, especially over the western
half of the area this afternoon. Even though unstable, a look at
both CAPE and LIs suggest a very borderline scenario and
probabilities for thunder for most locations ranging 10-20
pct...closer to 20 along the coast, closer to 10 pct east of the
Sound. The fact that there have been some thunderstorms overnight,
albeit elsewhere, lends enough support to keep them in the forecast
for today. Models allow this threat for thunder to persist into
Thursday. Once again, the emphasis remains on the western half of
the CWA, but this time the coastal waters, closest to the upper low,
see the higher chances. These again, however, are more to the 15-20
pct range while coastal land zones see a ProbThunder closer to 10
pct. NBM-derived forecast might be overdoing this threat just a tad,
pushing thunder chances all the way to the western shores of the
Sound. Will let that stand for now with the intent to revisit using
what happens today as a standard of evaluation.
The upper low plunges southward Thursday night, so while W WA will
still be under the influence of troughing, the low center pulls far
enough away to allow for diminishing chances for precip Thursday
night and Friday. Even as upper level ridging builds over the
Pacific Friday, there appear to be a couple of shortwaves embedded
in the leading edge of said ridge that will still allow for precip
chances Friday. Ensembles are not terribly impressed with chances,
mostly leaning toward slight chance wording /10-20 pct/. NBM might
be a little inflated, going for low-end chance wording /30-40 pct/,
but these variances do not appear to make a significant impact the
the general forecast overall, suggesting that Friday will likely be
more dry than wet.
Temps over the area will remain seasonable throughout the short
term, either right at climatological normals a slightly under.
18
.LONG TERM /SATURDAY THROUGH TUESDAY/...A Pacific upper level ridge
will take the reins /or will reign/ for the long term period,
keeping conditions dry over W WA for the remainder of the forecast
period. There is a weak shortwave Saturday which could result in
some showers for the first half of the day, but PoPs remain slight
at best. Dry conditions expected for the remainder of the forecast
period.
Daytime highs in the long term will still remain seasonable,
shifting slightly to near normal or a degree or two above.
18
&&
.AVIATION...Southwest flow aloft as an upper level low remains
offshore. On and off rain showers will continue over the area today
with generally VFR/MVFR conditions. Generally ceilings have been VFR
with these showers, but could see MVFR/IFR briefly at times under
heavier showers. Southerly surface winds 10 to 15 kts will continue
to remain into the afternoon, with occasional gusts up to  25 kts
throughout much of the area terminals. There is also a widespread 15-
20% chance of an isolated thunderstorm mainly around 18z-00z through
the interior, but as of now, confidence is too low to include in the
TAF.
.KSEA...VFR conditions this morning with a few showers around the
terminal. VFR likely will continue through the remainder of the day,
with a 20% chance of brief MVFR conditions under a heavier rain
shower or two at the terminal early this afternoon. Southerly winds
10 to 12 knots this afternoon with occasional gusts up to 20 to 25
kts at times. A chance of thunder (20%) exists later this afternoon
and evening, with not enough confidence for TAF inclusion at this
time.
28 &&
.MARINE...A strong frontal system will continue to move across the
area waters this morning, continuing to bring gale force winds
across the Coastal Waters, the Eastern Strait of Juan de Fuca, and
portions of the Northern Inland Waters. There will be a brief pause
in winds later this morning before southerly winds increase back
again to gale force. A Small Craft Advisory will remain for all
other interior waters.
The aforementioned frontal system will weaken into Thursday,
allowing for winds to gradually decrease over the area waters and
further weaken into the weekend, where additional systems may move
through the area waters but at this time will not have much impact
to wind and seas.
Combined seas this morning around 10 to 15 feet will quickly build
to 15 to 20 feet later this afternoon, with the largest seas (17-20
feet) being in the most outer coastal water zones. Most of the inner
water zones will see seas around 9 to 14 feet.
Seas look to quickly diminish by Thursday morning, around 10 feet.
28
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Wind Advisory until 5 AM PDT early this morning 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.
PZ...Small Craft Advisory until 5 AM PDT Thursday 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 AM PDT Thursday 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 early this morning for Puget
     Sound and Hood Canal.
Small Craft Advisory from noon today to 5 AM PDT Thursday for
     Puget Sound and Hood Canal.
&&
$$

NWS SEW Office Area Forecast Discussion