Western Washington

485 
FXUS66 KSEW 290325
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
825 PM PDT Sun May 28 2023

.SYNOPSIS...Onshore flow in the low levels will continue through
mid to late next week with morning clouds clearing for some
afternoon sunshine. Conditions will also remain mostly dry over
the week. Warmer conditions look likely late next week into next
weekend as a stronger ridge of high pressure over Canada begins to
build westward.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...Made a few adjustments
to the forecast this evening, mainly to account for cloud cover 
alongside the coast. The previous discussion still tracks and can
be found below along with updated aviation and marine discussions:

Generally clear skies this evening across the interior of Western
Washington. Another round of increasing onshore flow tonight into
Monday morning with stratus sliding inland during this period. 
Monday will feature morning clouds, clearing early afternoon-mid 
afternoon for sunshine. 

Onshore flow will be persistent through the middle of the week.
Troughing will develop further offshore and into BC on Wednesday
leading to a further increase in clouds at times and cooler
temperatures. Highs Monday will likely be in the 60s with a few
low 70s possible in the interior, with 60s Tuesday and Wednesday.

.LONG TERM /THURSDAY THROUGH SUNDAY/...Troughing will likely
continue offshore into Thursday, though weakening later in the
week. Ensembles are generally consistent in that of ridging,
located across central Canada, building westward Friday into the 
weekend. Some uncertainty exists into the extent of troughing
offshore, mainly Friday into Saturday, thus impacting
temperatures. However, a warming trend is likely to begin Friday,
continuing through the weekend with the building ridge.
Temperatures likely near normal Thursday, with highs into the 70s
to low to mid 80s over the weekend. JD/Mazurkiewicz

&&

.AVIATION...Weak upper ridging will gradually flatten and flow 
aloft will become more zonal into Monday as an upper level low 
enters the Gulf of Alaska well to the north of the local area.
Satellite imagery shows lingering stratus continuing to scatter
out across the central and south Sound this afternoon for a 
gradual return to VFR conditions for the area terminals. Once the 
remainder of the clouds scatter, can expect VFR conditions to 
persist through tonight. Low- level onshore flow will bring 
another round of MVFR (to localized IFR) marine stratus into the 
region by Monday morning - with the most likely timing looking to
be 03-06Z for coastal terminals and between 12-15Z for interior 
terminals. Expect stratus to stick around through the morning 
and to scatter toward 21Z. Southerly surface winds will continue
for most terminals through tonight with west winds expected for 
terminals near the Strait of Juan de Fuca (KCLM). Winds will then 
become light and variable overnight, generally persisting at 6 kt 
or less. 

KSEA...Stratus will continue to scatter at the terminal over the
next 1-2 hours for a return to VFR conditions. Southerly surface
winds persist, generally between 4-8 kt this afternoon. Expect 
winds to shift to the north overnight, but remain light - at 
6 kt or less. Winds will then become south/southwesterly again by
the mid-morning. Another round of MVFR stratus (likely between 
1500-2000 ft) is expected to move into the terminal early Monday,
most likely between 12-15Z. Stratus looks like it will be slow to
scatter, with conditions only improving near 21Z Monday. 14

&&

.MARINE...High pressure will remain situated over the waters the 
next several days, helping to maintain breezy northwesterly winds 
over the outer coastal waters at times and diurnal westerly pushes
down the Strait of Juan de Fuca. 

Guidance continues to suggest a slightly weaker push of westerly
winds along the Strait tonight than that of last night. While 
some isolated/occasional gusts to 35 kt cannot be ruled out, these
aren't expected to be widespread in the U.S. waters. Thus, a 
small craft advisory has been maintained for tonight along the
central and eastern portions of the Strait for sustained winds 
generally persisting at 20-30 kt. Westerly pushes on Monday and 
Tuesday appear stronger and thus, have issued a gale watch for the
westerly push on Monday evening. Winds will also likely increase 
again over the coastal waters on Monday, potentially yielding
additional small craft headlines.

Meanwhile, seas over the coastal waters will hover between 5 and 8 
feet today under persistent northwesterly winds - with the largest
seas expected beyond about 30 nm from the shore. Seas look to 
build to 7 to 9 ft on Monday and towards 9 to 11 ft on Tuesday for
the outer coastal waters. With seas dominated by short period 
fresh swell, expect quite choppy conditions to continue over the 
next few days. 14

&&

.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...Gale Warning until 1 AM PDT Monday for Central U.S. Waters 
     Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of 
     Juan De Fuca.

     Small Craft Advisory from 1 AM to 6 AM PDT Monday for Central 
     U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. 
     Waters Strait Of Juan De Fuca.

     Gale Watch from Monday afternoon through Tuesday morning for 
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance 
     U.S. Waters Strait Of Juan De Fuca.

&&

$$