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000
FXUS66 KSEW 120940
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
240 AM PDT Fri Apr 12 2024

.SYNOPSIS...Weak high pressure will begin to build over the region
on Friday and last throughout the weekend. A warming and drying
trend will take hold before upper-level troughing returns on
Monday with showers and cooler temps. But, signs are pointing
towards more ridging later next week.


&&

.SHORT TERM /TODAY THROUGH SUNDAY/...A weak front pretty much died
on arrival last evening as a few showers remain in its wake. The
associated upper-low is over the offshore waters of WA & OR and
will sink southward before making its way towards CA by the day`s
end. For us here locally, we`ll see drier conditions set up
across W WA today as weak ridging builds overhead. Near average
high temperatures are in the offing with values in the mid 50s to
lower 60s. Cooler spots are forecasted to be in and around the
coast with warmer locations within the interior. Overnight lows
will fall into the lower to mid 40s.

Benign conditions are expected through the weekend as the upper-
level pattern remains largely unchanged. The aforementioned
upper-low will gradually track towards the Great Basin by Sunday
evening. Weak upper-level ridging will persist over the PNW
leading to a rather pleasant stretch for both Saturday and Sunday.
Widespread 60s are in the cards during this time throughout the
interior. Coastal areas are to remain in the 50s. Overnight lows
will maintain in the lower to mid 40s also.

.LONG TERM /MONDAY THROUGH THURSDAY/...A pattern change will
arrive on Monday because of course, Monday. Temperatures are
expected to drop several degrees as upper-level troughing brings
the next round of widespread precipitation and lower snow levels
around 2,000 ft. A few showers are slated to remain on Tuesday but
things may trend drier again towards midweek. Deterministic
guidance indicates a ridge amplifying during this time but
questions remain on its exact location and intensity. Nevertheless,
the brief cool down to start the next may not last too long.

McMillian



&&

.AVIATION...Mainly MVFR with localized IFR as low to mid-level
clouds continue to spread inland behind a cold frontal passage.
Northerly flow will develop through the morning, increasing to 8-12
kt this afternoon. Isolated light shower activity will taper off
through the morning with cloud ceilings lifting to VFR by 18-20z Fri
with clouds scattering out by 22 Fri-00z Sat.

KSEA...MVFR to low VFR ceilings will remain in place through the
late morning before improving in the afternoon. Surface winds S/SW 4
to 7 kt will transition to northerly after 09Z tonight and increase
to 8 to 12 kt by early this afternoon.


&&

.MARINE...High pressure will continue to build over the waters today
with seas around 6 to 8 ft. High pressure will increase into
Saturday with offshore north winds reaching 15 to 25 kt as seas
increase to 8 to 11 ft. The gradient will intensify even more on
Sunday as a frontal boundary slides southward, causing a sharp
increase in onshore flow. This will likely lead to additional
headlines in the form of small craft advisory level winds for the
coastal waters and possible westerly gales in the strait Sunday
night. A sustained period of northwest winds over the coastal waters
this weekend into early next week is expected generate hazardous
seas in the form of short period swell at times.

Surface ridging will gradually rebuild early next week, allowing
seas to lessen by Tuesday to 5 to 7 feet with northerly winds over
the waters of 10 to 15 kt.

15


&&

.HYDROLOGY...No river flooding is expected through the next seven
days.


&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 5 PM this afternoon to 5 PM PDT
     Saturday for Coastal Waters From Cape Flattery To James
     Island 10 To 60 Nm-Coastal Waters From James Island To
     Point Grenville 10 To 60 Nm-Coastal Waters From Point
     Grenville To Cape Shoalwater 10 To 60 Nm.

&&

$$