610
FXUS66 KSEW 150955
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
255 AM PDT Wed May 15 2024

.SYNOPSIS...High pressure offshore will continue to provide warm
and dry conditions into early Thursday. An upper level trough will
dip down south from the British Columbia on Thursday afternoon
for cooler temperatures, more cloud cover, 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 a chance of showers.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...An upper level ridge mainly
located offshore will continue to build into our area today,
allowing for the generally warm and dry conditions to continue.
Low level onshore flow will keep coastal locations mainly in the
lower to mid 60s this afternoon, meanwhile, the more interior
locations will likely experience high temps in the low to mid 70s.

The aforementioned upper level ridge will begin to flatten into
Thursday, leaving room for a upper level trough to move in
from British Columbia, increasing onshore flow. A front will then
cross into western Washington on Thursday, bringing breezy winds
at times, a chance of showers, and cooler temperatures. Showers
look meager for the interior with this front, with most of the
precipitation aimed at the Northern Cascades. Snow levels look to
also gradually drop to around 4000 to 4500 feet on Thursday, but
any snow accumulations in the mountains will be light and mainly
be limited to the higher peaks in the backcountry. With increased
onshore flow, some model guidance is hinting at a convergence
zone developing over Skagit and Snohomish counties Thursday
evening. High temps will be around the low to mid 60s for the
interior, and upper 50s for locations near the coast and areas of
water.

The upper trough axis will move right across western Washington on
Friday, keeping it a cloudy day with the chance for some leftover
showers (with the best chance for showers being over the
mountains).

.LONG TERM /SATURDAY THROUGH TUESDAY/...Ensemble guidance still
show several solutions regarding the weekend, but cluster guidance
is starting to favor weak troughing over the Pacific Northwest.
Although troughing is being favored, it does not look like a
particularly wet solution, with most guidance hinting at below
normal temperatures and shower chances sticking around through the
long term. The best bet for any showers this weekend looks like to
be mainly in the higher terrain. Unsettled weather looks to
continue into the first half of next week.

Mazurkiewicz

&&

.AVIATION...Northwesterly flow aloft will continue over W WA into at
least Thursday morning as upper level ridging remains over the
eastern Pacific. Surface winds light and northerly for most
terminals with only BLI reporting more southerly.

Largely VFR conditions area-wide with some high clouds overhead
largely east of the Sound or over the western half of the Olympic
peninsula. UIL and CLM reporting IFR conditions, however it is
worth noting that CLM is bouncing around, sometimes clear, other
times with BKN low clouds. Have the lower cigs in a TEMPO group and
given the yo-yo nature of the obs, this appears to be the best way
to handle it at this time. VFR conditions expected to remain in
place for most terminals, however will see cigs gradually lower
throughout the day in anticipation of incoming system for Thursday.
HQM is worth noting here in that cigs may fall enough to dip down
into MVFR this afternoon.

KSEA...VFR with mainly high cirrus for the TAF period. While some
low confidence hints at MVFR conditions emerging early this morning,
a large T-Td difference suggests chances of this close to nil. As
mentioned above, cigs will gradually lower throughout the day,
however still remaining at or above 10000 ft. Northerly winds 4-8
kts through at least 18Z, then speeds increasing to around 5-10 kts
for the afternoon and evening.

18

&&

.MARINE...High pressure/upper-level ridging will continue to build
over the Pacific through the week, resulting in northwest flow
translating to north/northwest surface winds. Another round of SCA
level winds expected in the Strait starting this afternoon and
potentially continuing into Thursday. That said, will be issuing a
new round of headlines with the morning forecast package. A stronger
push is expected to accompany an incoming frontal system Thursday
night and Friday which may need yet another set of headlines. Winds
expected to ease for most areas, save perhaps the outer coastal
waters this weekend into early next week.

Seas will hold around 4 to 6 ft through Friday before increasing 8
to 12 ft from Friday into the weekend, reducing to 6 to 8 ft 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 until 5 AM PDT early this morning for
     Central U.S. Waters Strait Of Juan De Fuca-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.

&&

$$