481
FXUS66 KSEW 151607
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
907 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.

&&

.UPDATE...Forecast below remains on track for the short term and
extended periods. Temperatures today are already in the 50s and
low 60s this morning, and are on track to climb into the upper 60s
and low to mid 70s today. See details below as well as a refreshed
aviation section.

HPR

&&

.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, CLM and HQM are reporting IFR conditions. 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.

KSEA...VFR with mainly high cirrus for the TAF period. 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. MVFR is possible going into late tonight
along with convergence zone activity in the vicinity.

18/McMillian

&&

.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 Thursday for Central U.S.
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 5 PM this afternoon to 5 AM PDT
     Thursday for East Entrance U.S. Waters Strait Of Juan De
     Fuca-Northern Inland Waters Including The San Juan Islands.

&&

$$