-- Discussion containing changed information from previous version are highlighted. --
019
FXUS66 KSEW 122048
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
148 PM PDT Wed Jun 12 2024

.SYNOPSIS...
-- Changed Discussion --
Ridging will nudge into Western Washington through
Thursday for drier weather and slightly warmer temperatures.
Troughing Friday through early next week will bring unsettled
weather, including potential thunderstorms over the weekend.
Lingering troughing possible into the middle of next week.
-- End Changed Discussion --

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...
-- Changed Discussion --
Dry conditions this
afternoon with scattered cumulus across portions of Western
Washington. Ridging will continue to nudge into Western Washington
through Thursday for drier conditions and slightly warmer
temperatures. Patchy fog possible tonight into Thursday morning
for the local river valleys and into Southwest Interior.
Otherwise, highs will be in the mid 60s to low 70s through
Thursday.

Troughing will develop offshore Thursday night and move towards
the area on Friday as an associated front moves across the area.
This will begin a period of more unsettled weather and cooler
temperatures. Showers will initially increase along the coast
early Friday morning, with increasing precipitation for the
interior Friday afternoon. Temperatures Friday will be a few
degrees cooler with highs in the upper 50s to mid 60s.

Troughing will move overhead Saturday through the weekend,
ushering in cooler temperatures aloft. Surface instability will
increase post-front on Saturday with potential thunderstorms
across Western Washington. Current probabilities are highest
across central Puget Sound (generally 25-35% chance) due to likely
convergence zone activity. Any thunderstorm may be accompanied by
frequent lightning, small hail, and brief gusty winds. Shower
activity will continue into Saturday night, though the threat of
thunderstorms becomes limited following sunset. Saturday will
likely be the coolest day of the stretch with highs in the mid 50s
to low 60s.

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Troughing will be
reinforced Sunday across the Pacific Northwest for continued
unsettled weather, including scattered showers, and a slight
chance of thunderstorms. Troughing slowly slides east Monday into
Tuesday, but given the proximity of the trough, slight
precipitation chances remain, primarily in the mountains with more
northerly flow. Uncertainty remains as to the degree of troughing
into the middle of next week, but some slight warming may occur
Tuesday into Wednesday. JD
-- End Changed Discussion --

&&

.AVIATION...
-- Changed Discussion --
Westerly flow in the midlevels today, becoming more
southwesterly late Thursday morning as an upper low digs southward
across the Gulf of Alaska. Satellite shows clouds continuing to
scatter across the region this afternoon. Conditions at the area
terminals are VFR and expect most sites to remain so through this
evening and into the overnight period. Some patchy fog development
will be possible overnight, mainly along the coast and across portions
of the Chehalis River Valley. Latest NBM probabilistic guidance
has roughly a 35 percent chance of KHQM seeing a few hours of MVFR
conditions on Thursday morning. Probabilities across the south
Sound terminals are lower, with only a 15 percent chance of
conditions becoming MVFR at KOLM. Thus, any terminals in fog could
see some brief MVFR, or even IFR, conditions for few hours in the
morning. Expect fog to dissipate for a return to VFR by late
Thursday morning. Flow in the low levels will remain northerly
through the TAF period. Winds at the surface generally persisting
out of the N/NE between 7-12 kt. Winds will become light this
evening and will continue out the N into Thursday, increasing to
5-10 kt during the afternoon hours.

KSEA...VFR conditions will persist into Thursday. Winds generally
persisting out of the N/NW this afternoon at 7-12 kt. Winds will
become light overnight, shifting to the NE. Winds will increase
to 5-10 kt again by Thursday afternoon. 14
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
High pressure building over the offshore waters has
allowed for conditions to gradually calm across the majority of
the area waters today. Seas have started to subside across the
coastal waters, currently persisting at 7-9 ft, and winds have
eased below small craft criteria along the Strait of Juan de Fuca.

Northerly winds will increase a bit tonight along the coastal
waters south of Point Grenville as the surface ridge continues to
nose into the region and interact with a surface trough over
northern CA/southern OR. A Small Craft Advisory remains in effect
for the southernmost inner coastal zone this afternoon into
tonight. Another push of westerly winds will occur along the
Strait tonight. While occasional gusts to 25 kt will be possible
at times in the central and eastern Strait, the majority of the
guidance suggests that winds will generally remain between 10-20
kt into Thursday.

High pressure offshore will weaken on Thursday as the next frontal
system approaches the region. Onshore flow will continue, with
another, stronger push of westerlies expected along the central
and eastern Strait Thursday night into Friday. The next front
will then move across the region Friday into Saturday, allowing
for winds to transition back to the south. Additional pushes of
westerlies look likely down the Strait Friday and over the
weekend. The pattern looks a bit more uncertain heading into early
next week, though could see high pressure briefly build back into
the coastal waters with additional systems weakening as they
approach the region.

Seas will continue to subside into Thursday, persisting at 6-8 ft.
Seas will then subside towards 4-6 ft over the weekend and generally
look to persist in this range headed into early next week. 14
-- End Changed Discussion --

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
WA...None.
PZ...Small Craft Advisory from 5 PM this afternoon to 1 AM PDT
     Thursday for Coastal Waters From Point Grenville To Cape
     Shoalwater Out 10 Nm.
-- End Changed Discussion --

&&

$$