University Place, Washington Weather Forecast Discussion

465
FXUS66 KSEW 282209
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
309 PM PDT Sun Sep 28 2025
.SYNOPSIS...A couple of frontal systems will pass through western
Washington this week. The first one arrives tonight into Monday,
with a second, more prolonged system midweek. Widespread steady
rain with a low chance of thunder, and breezy to gusty winds are
the main impacts with these systems. Temperatures will also cool
off slightly this week, with highs only reaching the low to mid
60s, and lows in the upper 40s to 50s.
&&
.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...It`s a dry afternoon
across western WA, as weak high pressure inland begins to weaken
and move east tonight High clouds are beginning to fill inland
this afternoon ahead of the next system offshore. Quite a bit of
sun still out there, so many spots are still seeing temps in the
upper 60s to low 70s this afternoon, and may continue to climb
another degree or two before the evening.
The pattern changes significantly tonight into Monday - much more
like late autumn with the first of a couple of surface systems
passing through tonight/Monday. An upper level low/trough from the
Gulf of Alaska will dig southward and deepen offshore this week.
A shortwave trough will pass over the west coast Monday. driving
a surface cold front through the region. Rain and wind are the
primary concerns with this system. The first band of rain is
expected to reach the coast after midnight, reaching the interior
during the morning commute. Winds will pick up out of the
southeast ahead of the rain. The windiest areas are the coast/NW
interior (western Whatcom County) with mean HREF ensemble members
showing peak gusts up to 35 mph (very low chance of a gust
exceeding 40 mph). The thunder threat remains very low, but can`t
rule out an isolated thunderstorm with the strongest rain bands.
Rain will wrap up Monday evening. Heaviest rain amounts are
expected along the coast/Olympics, with amounts of 0.50-1.00"
(convective banding may produce slightly heavier amounts over the
Olympics and the north coast). The interior will most likely see
0.10-0.25", with the north Cascades seeing 0.50-1.00" and locally
heavier amounts over mountain peaks.
A break in widespread rain is expected Monday night through
Tuesday afternoon before a stronger frontal system approaches the
coast. WPC surface analysis has the low deepening down to 977 mb
prior to moving inland on Wednesday. The duration of this system
is expected to last from Tuesday evening through most of Thursday,
with more rain and wind. The strongest southeast winds are
expected from Tuesday evening into Wednesday, with a 40-60% that
coastal areas may see wind gusts over 40 mph. Interior areas will
most likely see gusts of 15-25 mph with this system. Rain remains
the biggest uncertainty (especially as cool air aloft will likely
increase the probability of convective with a few isolated
thunderstorms). The Cascades and Olympics/coast will see the most
rain, with a 60-80% chance of these areas exceeding 2" of rain
Tuesday through Thursday (40-60% chance of total rain exceeding
3"). 6 hourly rain rates may approach half an inch in these areas.
In addition to rain and wind, wave heights along the coast will
approach 15 ft and higher on Wednesday. This may lead to some
beach erosion due to coastal flooding, and high surf conditions.
Cooler temperatures will keep highs in the 60s through the week,
with lows dropping into the 50s and upper 40s.
.LONG TERM /THURSDAY THROUGH SUNDAY/...The ensembles still have
some discrepancies with how the low will track inland going into
Thursday (the GFS gives a more southern track towards Oregon,
while the Euro gives a more northern track into Canada with the
trough filling/weakening). The track may add or subtract
precipitation to the total amount of rain expected in the
Tuesday-Thursday period. The southern track would likely leave a
quick dry period towards the end of the week before another
disturbance passes to the north, keeping shower chances in the
forecast for the foreseeable future (next seven days). Though the
amount of QPF/precipitation expected drops substantially after
Thursday.
HPR
&&
.AVIATION...Mid to high level cloud cover will continue to increase
over the region tonight ahead of the next frontal system, with
increasing southerly breezes this afternoon and evening. Expect the
frontal system moving across the area late tonight through Monday.
Expect rain to reach the coast this evening and pushing into Puget
Sound around 12z Monday. Expect gusty southerly winds to 25 kt and
lower ceilings and reduced visibility in rain as the front pushes
through. Gradually improving conditions Monday afternoon with
residual showers tapering late.
KSEA...Increased mid level clouds through the afternoon and evening
ahead of the approaching front. Winds relatively light today, but
increasing southeasterly winds early Monday morning with gusts to
25 kt around the frontal passage. This front will bring lower
ceilings and visibility in rain. Conditions gradually improve
Monday afternoon as showers end.
&&
.MARINE...A frontal system will move through the coastal waters
late tonight into Monday. Southerly winds will continue to
increase this afternoon across the coastal waters, though not
increasing through the interior waters until late tonight into
early Monday morning as the front will be slow-moving. The front
should pass through the coastal waters overnight allowing winds to
ease. Winds remain elevated Monday morning across the interior
waters through Monday morning though will ease by Monday
afternoon. Winds will continue to remain at Small Craft Advisory
strength across the coastal waters as well as Admiralty Inlet and
the North Interior Waters. Frequent gusts up to gale force are
expected in the East Strait of Juan de Fuca.
A stronger frontal system will 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. With continued high confidence in gale
force winds, have gone ahead and issued a Gale Watch for the
aforementioned areas from early Tuesday morning through Wednesday
morning. Most remaining marine zones will likely see winds of at
least SCA criteria during this period.
Winds will decrease throughout the day Thursday and into Friday
as the low pressure system weakens as it moves inland. High
pressure will build over the northeast Pacific again late in the
week, shifting winds back to the northwest over the coastal
waters.
Seas of around 8 to 9 ft will increase to around 10 to 12 ft
across the coastal waters tonight as the front moves through.
Waves will rise once again on Tuesday, up to around 15-18 ft.
Waves will be southerly associated with the frontal passage, then
switch to westerly by Wednesday. Waves will ease below 10 ft on
Thursday.
62
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Gale Warning from 8 PM this evening to 11 AM PDT Monday for East
     Entrance U.S. Waters Strait Of Juan De Fuca.
Gale Watch from late Monday night 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 from 8 PM this evening to 11 AM PDT Monday
     for Admiralty Inlet-Northern Inland Waters Including The
     San Juan Islands.
Small Craft Advisory until 5 AM PDT Monday 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.
&&
$$

NWS SEW Office Area Forecast Discussion