761
FXUS66 KSEW 161612
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
912 AM PDT Thu May 16 2024

.UPDATE...Cold front edging closer to western Washington this
morning as it`s currently over southern BC. For today, wetter
conditions and cooler temperatures remain in store. Rain showers
will push form north to south today along with convergence zone
activity developing later this evening over central Puget Sound.


&&


.SYNOPSIS...An upper level trough will dip down south from the
British Columbia today for cooler temperatures and a chance for
showers mainly in the northern portions of our region. Unsettled
weather looks to continue through the weekend and into early next
week, with cooler temperatures and more chances of showers. High
temps are to range between the mid 50s to mid 60s. The previous
discussion is below along with an updated marine/aviation
section.

&&

.SHORT TERM /TODAY THROUGH SATURDAY/...An upper level trough will
continue to move southward from British Columbia through this
afternoon, with a weakening cold front swinging through western
Washington into this evening. A chance of showers will return
throughout the day with breezy winds at times and slightly cooler
temperatures. Moisture looks mostly confined throughout the
Northern Cascades, with the best chance of showers being primarily
there. As the aforementioned cold front swings through the area,
onshore flow will also increase behind the front, leading to
breezy winds at times throughout the lowlands. Latest hi-res
guidance suggests a convergence zone to develop post-frontally
near western Skagit and Snohomish counties later this evening..
with likely higher precipitation amounts within the convergence
zone.

Snow levels look to drop around 3000 to 3500 feet as well, with
some light snow accumulations in the higher peaks in the
backcountry. High temperatures this afternoon will be around the
mid 60s for the interior, and in the upper 50s for locations near
the coast and areas of water.

The upper trough axis will swing directly above western Washington
on Friday, with some leftover showers staying in the higher
terrain in the Cascades. Most of the interior should remain dry
with clouds breaking up for some. Temps will continue to remain in
the mid 60s. A weak shortwave will pulse through the region on
Saturday, keeping the unsettled weather trend going with another
chance of showers for the area. Precip looks light and will likely
continue to stay focused in the Cascades.

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Ensemble guidance and
clusters are in general agreement for troughing to continue over
the Pacific Northwest, with several disturbances tracking across
our region in the long term. Temperatures will remain at or just
below average through Wednesday, with light shower chances likely
each day, although shower chances look spotty in coverage.

Mazurkiewicz

&&

.AVIATION...West to northwesterly flow aloft throughout the day
today as an upper level trough starts to dip into W WA. Surface flow
generally southerly throughout the day with lighter winds this
morning before becoming gusty this afternoon and evening.

Cigs already feeling impacts from the incoming frontal system
this morning, with observations showing a mixed bag of VFR, MVFR
and IFR. A few spots have briefly seen LIFR conditions in drizzle
this morning as well. Expect more widespread MVFR to IFR conditions
to develop through the morning. Some improvement to high- end
MVFR can be expected this afternoon with VFR conditions returning
this evening and tonight. The exception will be in locations that
tend to favor lower cigs such as HQM, OLM where recoveries should
nudge them just into low- end MVFR range. Showers will be possible
today, but favored terminals look to be HQM and BLI. A convergence
zone looks to develop across the central Sound this evening,
and looks to dissipate overnight.

KSEA...MVFR cigs in place this morning, though have seen some
reductions to IFR to LIFR conditions. Some light shower activity
will be possible today. There is the prospect for some convergence
zone activity, but latest model trends continue to suggest that
activity will remain north or east of the terminal, however this
will continue to be monitored throughout the day.

18/14


&&

.MARINE...Breezy to windy conditions with the incoming frontal
system will keep headlines in the marine forecast for much of today
and possibly into Friday. While previous models suggested a brief
break in the winds in the Strait this morning, data no longer
supports that outcome. As such, decided to not get fancy with the
forecast and simply extended inherited headlines to cover at least
most of the event expected today. Inherited SCA for coastal waters
looks good and will remain untouched. Otherwise, remaining interior
waters look to reach into SCA criteria at varying times and have
staggered their headlines accordingly. Headlines in the Strait will
likely need extension into Friday, but will leave that for following
shifts. Winds expected to ease for most waters, save perhaps the
outer coastal waters this weekend into early next week.

Seas will hold around 4 to 6 ft today before increasing 8 to 12 ft
from Friday into the weekend, reducing to 6 to 8 ft early next week.

18


&&

.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 5 PM this afternoon to 11 AM PDT
     Friday for Admiralty Inlet-West Entrance U.S. Waters Strait
     Of Juan De Fuca.

     Small Craft Advisory until 11 AM PDT Friday for Central U.S.
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
     Strait Of Juan De Fuca-Northern Inland Waters Including The
     San Juan Islands.

     Small Craft Advisory from 5 PM this afternoon to 5 AM PDT Friday
     for Puget Sound and Hood Canal.

     Small Craft Advisory from 2 PM this afternoon to 11 AM PDT
     Friday 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.

&&

$$