Gale Warning 19, NWS Seattle, WA

Area Forecast Discussion
National Weather Service Seattle WA
905 AM PDT Mon Sep 29 2025

.SYNOPSIS...A frontal system will push through Western Washington
today. A stronger frontal system is expected Tuesday through
Wednesday. These systems will bring widespread rain, breezy to gusty
winds, and a slight chance of thunder. Unsettled conditions are
favored to continue late into the week as additional systems move
into the region.

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.SHORT TERM /TODAY THROUGH WEDNESDAY/...The main band of precip
associated with a splitting frontal system continues to progress
eastward across Western Washington this morning. QPF will remain
relatively light with this system, but this sets the stage for a 120
knot jet max offshore to direct a stronger system into the region
tomorrow into Wednesday. The main impacts will be gusty winds
(especially coast and North Interior) and locally heavy precip over
the Olympics. Current forecasts are on track. 27

A frontal system continues to push across Western Washington early
this morning. Latest satellite imagery as of 350 AM shows light to
moderate rain making its way along the coast and a few light showers
moving across the interior locations. This weather system will bring
breezy to gusty winds to the coast, locations along the east Strait,
and northern interior Monday morning. There is high confidence (80-
90% chance) of seeing wind gusts exceed 25 mph for the east Strait
and Whidbey Island, while there is medium to high confidence (50-80%
chance) for the northern interior. There is medium confidence (40-
65% chance) of seeing wind gusts exceed 35 mph for locations along
the east Strait and Whidbey Island. There is a slight chance (10-
25%) of thunder this afternoon, with the highest chances along the
Olympic Peninsula and Cascades. Rainfall totals with this system
will range between 0.10-0.50 inches in the interior, 1.00-2.00
inches for the Olympics and Cascades, and 0.50-1.00 inches along the
coast.

A stronger frontal system associated with an upper level low
offshore will move through Western Washington Tuesday through
Wednesday. This system will bring more rain than the last system.
WPC has included the Olympic Peninsula under a marginal risk for
their Excessive Rainfall Outlook, indicating at least a 5% risk
for significant rainfall. Latest guidance suggests, the Olympic
Peninsula may see between 2.00-4.00 inches of rain, with higher
amounts in the mountain peaks. As for other locations, 0.25-1.00
inches in the interior and 1.00-3.00 inches in the Cascades. In
addition, this system will bring breezy to gusty winds and the
chance for thunder. There is high confidence of seeing wind gusts
exceed 25 mph along the coast, east Strait, Whidbey Island, and
northern interior. Stronger winds will be along the coast, east
Strait, and Whidbey Island, where there is medium confidence
(40-60% chance) of seeing gusts exceed 35 mph. Latest model runs
have trended higher on the chance of thunder for Tuesday and
Wednesday. On Tuesday thunder chances (20-30%) will be mostly
confined to the coast, with a smaller chance (10-15%) in the
interior. On Wednesday evening , thunder chances are slightly
higher; guidance suggests a 20-40% chance for the Olympic
Peninsula and a 15-20% chance for other locations.

Wave heights along the coast will approach 15 feet or higher on
Wednesday. This may generate hazardous surf conditions with waves
running higher on beaches that can sweep people off jetties and
breakwaters. Beach erosion is also possible.

.LONG TERM /THURSDAY THROUGH SUNDAY/...Latest deterministic
models and ensemble data are coming to a general agreement that the
center of upper level low offshore will move through Western
Washington on Thursday. This will keep unsettled conditions late
into the week. However, uncertainty still remains over the weekend
on the upper level pattern. Latest ensemble guidance shows zonal
flow is likely behind the upper level low on Friday with with
another upper level trough following on Saturday and Sunday.

29

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.AVIATION...Southwesterly flow aloft will persist through the TAF
period with upper level troughing over the region. A slow moving
frontal system will continue to push inland this morning, bringing
rain and gusty southerly winds to the area terminals. Radar shows
the heaviest rain continuing to push inland along the coast this
morning, with the bands of heavier precipitation likely to push
inland into the interior terminals through this afternoon. Expect
ceilings to lower towards MVFR and for terminals to see reduced
visibilities as the front pushes through. Gusty southerly winds to
25 kt will also be possible for area terminals, particularly at BLI
and through the north interior, ahead the front this morning.
Winds will ease as the front moves through the area this afternoon.
A slight chance of thunderstorms is possible area- wide this
afternoon and evening, but confidence in occurrence is too low to
include in TAFs at this time. Gradually improving conditions are
then expected by the afternoon with residual showers tapering this
evening. Not much of a break before the next frontal system
approaches the coast Tuesday morning with winds increasing and heavy
rain for the coastal terminals by 18Z Tue.

KSEA...VFR conditions continue this morning as rain reaches the
terminal. SE winds will continue and remain in the 5-10 kt range,
with some gusts to 15-20 kt possible as the front passes through
this afternoon. Ceilings and visibilities will lower towards MVFR
conditions as the front moves through and rain continues. Conditions
look to gradually improve this evening, with showers tapering
tonight. Ceilings look to lower to IFR or lower early Tuesday
morning with potential visibility restrictions in mist/fog.

14/62

&&

.MARINE...A slow-moving frontal system will continue to cross the
area waters this morning, bringing gusty winds to the coastal
waters, the Eastern Strait of Juan de Fuca, Admiralty Inlet, and the
Northern Inland Waters. Frequent gusts to gale force will continue
for East Strait through the late morning hours. Winds will then ease
again by this afternoon for a brief lull in between systems. Latest
observations continue show steep seas across the coastal waters with
seas around 10 ft with dominant periods around 8 to 12 seconds. Seas
will become less steep through the morning and will gradually
subside back to 8 to 9 ft.

A stronger frontal system will then move across the area waters
Tuesday into Wednesday, likely bringing gales to the coastal waters,
the Eastern Strait of Juan de Fuca, and portions of the Northern
Inland Waters. Confidence remains high in the occurrence of gales,
with latest probabilistic guidance showing a 75-90 percent
probability of gale gusts across the coastal waters and a 45-55
percent probability across the East Strait/Northern Interior Waters.
Thus, a Gale Watch remains in effect for these areas. Elsewhere, the
majority of the remaining marine zones will likely see gusty winds
of at least SCA criteria during this period. Waves over the coastal
waters will build towards 15-18 ft and will primarily be southerly
associated with the frontal passage, then will transition to more
westerly by Wednesday.

Winds will decrease through the day Thursday and into Friday as the
low pressure system associated with the front weakens and starts to
move inland. Seas will gradually fall back below 10 ft on Thursday.
High pressure will then build back into the northeastern Pacific
late in the week, shifting winds back to the northwest over the
coastal waters.

14/62

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Gale Warning until 11 AM PDT this morning for East Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Gale Watch from late tonight through Wednesday morning 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.

     Small Craft Advisory until 11 AM PDT this morning for Admiralty
     Inlet-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-Northern
     Inland Waters Including The San Juan Islands.

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