737
FXUS66 KSEW 162254
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
254 PM PST Thu Jan 16 2025

.SYNOPSIS...A weak frontal system will exit the region this
evening as lingering shower chances gradually end. Surface high
pressure will rebuild offshore tonight and remain the main weather
factor into the middle of next week. This will result in drier
and colder weather


&&

.SHORT TERM /TONIGHT THROUGH SUNDAY/...A weak front is currently
crossing east of the Cascades. In its wake, a convergence zone is
raining over King/Snohomish Counties. HREF guidance has this
feature persisting this evening before gradually fading into
Friday morning. For tonight, chilly conditions are in store with
lows forecast to bottom out in the 20s and 30s. Patchy fog/low
stratus is likely again into Friday morning as well.

Drier conditions are favored into Friday as an upper-ridge builds
offshore. W WA is along the leading edge of the ridge as cool
north-northwest flow aloft ushers in. A subtle 700mb vort max is
being hinted at by global models so can`t rule out a stray shower
or two during the day, primarily over the mountains but again
mostly dry conditions are expected. This pattern will remain
locked through the weekend as ridging parallels the US West Coast
with broad troughing over the rest of CONUS. Although conditions
are to remain benign, cold overnight lows are expected.
Confidence is increasing in widespread 20s for low temperatures
throughout the weekend. Cold weather may cause impacts to
vulnerable populations, infrastructure, etc. High temperatures are
to top into the 40s.


.LONG TERM /MONDAY THROUGH THURSDAY/...Models have ridging
remaining into early next week. However, a gentle shift eastward
will allow the pattern to reopen briefly as a weak front brings
the return of slight PoPs into the forecast. Shortly afterward,
stubborn ridging will return by Wednesday-Thursday as the mostly
dry trend continues. Min temps will remain in the 20s and 30s with
daily highs in the 40s.


&&

.AVIATION...A weak cold front continues to move through Puget Sound
this afternoon underneath an upper level trough. The location of the
front as of 22Z is just west of Puget Sound (evident by a weak
convergence zone band of showers moving through Seattle and with
winds beginning to turn to the west just behind the front in Whidbey
Island/Admiralty Inlet area). Some of the IFR/LIFR
ceilings/visibilities are beginning to erode, particularly within
Puget Sound as the front moves through. While a couple pockets of
VFR ceilings are possible at times this afternoon (particularly
along the coast and Strait of Juan de Fuca/San Juan areas),
remaining inland areas will likely remain MVFR through tonight.
Areas out ahead of the front still will see winds turn to the
north/northeast at 6 to 8 kt this afternoon/evening (west for areas
west of Puget Sound), and decrease to under 5 kt tonight. Ceilings
tomorrow morning will be borderline MVFR/IFR (with LIFR clouds or
fog possible from East Olympics down to the Chehalis Valley, and the
Cascades). Clearing is expected Friday afternoon with increased
northerly flow aloft.

KSEA...Terminal improved to MVFR as of 22Z (still could be sporadic
areas of mist or lower ceilings through the afternoon but these will
go away once the front moves through). Ceilings expected to remain
MVFR (but will drop close to IFR tonight/Friday morning). Winds this
afternoon are expected to transition to the northeast once the
convergence zone/area of showers move through the terminal. Couple
of these winds at the surface will be 6 to 8 kt, but will be under 5
kt this evening into much of tomorrow.

HPR

&&

.MARINE...A weak cold front is currently located over the East
Strait of Juan de Fuca, west of the Puget Sound waters this
afternoon. The onshore flow behind this front continues, but will
gradually weaken going into tonight as high pressure follows the
front onto land through the weekend. Gusty winds this afternoon will
continue to diminish in the Strait of Juan de Fuca (and linger into
Friday morning in the coastal waters). Gradients this weekend will
be northerly or offshore. Seas will drop down from 6 to 8 feet
today/Friday to 4 to 6 feet this weekend, with another round of 6 to
8 foot waves Sunday into Monday.

HPR


&&

.HYDROLOGY...No river flooding expected in the next 7 days.


&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 10 PM PST this evening 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-West Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 4 PM PST this afternoon for Central
     U.S. Waters Strait Of Juan De Fuca-East Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 10 AM PST Friday 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.

&&

$$