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000
FXUS66 KSEW 191619
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
919 AM PDT Fri Apr 19 2024

.SYNOPSIS...Upper level ridge offshore today moving east through
Western Washington late tonight and Saturday morning. Next front
arriving Saturday evening. Upper level trough behind the front
late Saturday night into Sunday morning moving into Eastern
Washington Sunday afternoon. Upper level ridge building offshore
Sunday night moving through Western Washington Monday. Weak upper
level trough over the area later Tuesday and Wednesday with
another front possible for Thursday.

&&

.SHORT TERM /TODAY THROUGH SUNDAY/...Satellite imagery shows clear
skies over Western Washington this morning. Cross cascade
gradient has turned negative with easterly winds picking up in the
Cascade foothills and along the coast. Wide variety of
temperatures at 3 am/10z. Locations not exposed to the east winds
in the mid to upper 30s while locations with some easterlies in
the upper 40s.

Upper level ridge offshore moving into Western Washington today.
This combined with the increasing offshore flow will give the area
a warm day. High temperatures around 10 degrees above normal, in
the 60s to mid 70s. Expect the coast and Cascade foothills to be
the warmest locations.

Upper level ridge axis over Western Washington tonight with a
low level offshore flow continuing into Saturday morning. Like
this morning, locations exposed to the east winds will only drop
into the 40s while more sheltered locations like Olympia get as
cold as the mid 30s.

Ridge axis moving east of the area by late Saturday morning. Front
offshore approaching but with the jet digging into the southern
portion of the front the front will become negatively tilted
slowing down its eastward progress. Rain west of the Puget Sound
by afternoon with a chance of rain over most of the interior. The
Northwest Interior still looks dry through the afternoon hours.
High temperatures are going to be a tough call. Low level offshore
flow continuing but the increasing middle level clouds will
reduce the amount of daytime heating over the interior.
Significantly cooler along the coast with highs near 60. Slightly
cooler over the interior with highs in the 60s. A few places in
the Cascade foothills could still get to 70 degrees.

Rain changing to showers after midnight Saturday night as the
front moves through Western Washington. Unlike last night where
the models were showing a cold pool of air behind the front along
the coast, the models this morning have this cold pool well to the
north near Haida Gwaii. Will not have any post frontal
thunderstorms mentioned for the coast this morning. Snow levels
near 5000 feet ahead of the front with a few inches of snow in the
higher elevations especially in the North Cascades. Snow levels
dropping to 3000-3500 feet behind the front early Sunday morning
but the main batch of precipitation is with and ahead of the front
leaving only a couple of inches of snow for the passes. Lows
Saturday night in the upper 30s to mid 40s.

Upper level trough behind the front over Western Washington
Sunday morning moving into Eastern Washington Sunday afternoon.
Shower activity over the lowlands decreasing in the afternoon.
Cool air aloft plus low level onshore flow making for a brisk day
with highs only in the lower to mid 50s.

.LONG TERM /MONDAY THROUGH THURSDAY/...Extended models in good
agreement with an upper level ridge building offshore Sunday night
moving into Western Washington Monday. Under sunny skies highs
warming into the upper 50s to mid 60s. Ridge shifts east Monday
night with an upper level trough approaching Western Washington
Tuesday. With the trough staying offshore we should squeeze out
one more dry day with highs again in the upper 50s to mid 60s.
Model consistency falls apart Tuesday night through Thursday.
There is general agreement that an upper level trough will be over
Western Washington Tuesday night into Wednesday night with the
ECMWF weaker with this feature versus the GFS. ECMWF has an
organized front moving into the area Thursday while the GFS has
this system moving inland south of the area. Ensembles don`t show
any clear trend so given the uncertainty will have chance pops in
the forecast Tuesday night through Thursday. Highs Wednesday
cooling into the mid 50s to lower 60s. Thursday even cooler with
mid to upper 50s. Felton

&&

.AVIATION...Flow aloft will remain out of the northwest through the
TAF period as an upper level ridge continues to build offshore. A
thermal trough also remains positioned off the coast for offshore
flow continuing. Weather remains dry as well with VFR
conditions/clear skies expected. Breezy east to northeast winds
across the region, with occasional gusts to 15 to 20 kt. Winds will
likely decrease a bit this evening but struggle to get very light. A
frontal system will arrive later on Saturday for breezy winds and
the next chance for precipitation.

KSEA...VFR/clear skies through the TAF period. Winds easterly 8 to
12 kt, easing to around 4 to 8 kt in the evening. Winds turn
southwesterly and breezy ahead of the next system coming in.

Kristell/LH

&&

.MARINE...An upper level ridge will begin to move inland
today. A thermal trough remains positioned off the coast of
Washington for continued offshore flow. The next approaching system
for this weekend will promote some breezy winds with some gusts
reaching 20 to 25 kt in the Central Strait of Juan de Fuca into this
afternoon and evening, for which there is a Small Craft Advisory.
Additional gusty winds are possible Saturday and Sunday with the
next system, including potential westerly gales in the Strait.

Seas remain around 3 to 6 ft through Saturday, before rising to 10
to 12 feet on Sunday. Seas may be steep over the weekend with
short period waves being the dominant group.

Kristell/LH

&&

.HYDROLOGY...No river flooding expected over the next 7 days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 8 PM PDT this evening for Central
     U.S. Waters Strait Of Juan De Fuca.

&&

$$