National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS66 KSEW 121618
AFDSEW

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

.SYNOPSIS...Weak high pressure will begin to build over the region
today and last throughout the weekend, bringing with it a warming
and drying trend. Upper-level troughing returns on Monday with
showers and cooler temps. This will only be a brief interlude as
upper level ridging is expected to return for much of next week.

&&

.SHORT TERM /TODAY THROUGH SUNDAY/...Upper level low pressure
continues to sink southward today, dragging its associated moisture
with it. While this circulation will continue to push high clouds
over the area...as seen on current satellite...the influence of a
building weak upper level ridge will remain the dominant weather
feature for today and into the weekend. Going back to current
satellite, still some lingering low clouds present...mainly along
the lowlands of the eastern Sound, along the Strait, in the SW
interior and along the central coast. Continued gradual improvement
is expected in these spots which should reveal at least partly sunny
skies for the afternoon.

As already mentioned, weak upper level ridging will be the main
headline for the short term, not only making for dry conditions but
also with warmer daytime highs. Mid 50s to around 60 expected in the
interior lowlands today then warming even further to the lower to
mid 60s for Saturday. A little cooling is expected Sunday ahead of
the next frontal system...most notably along the coast where temps
will cool back into the mid to upper 50s while the interior remains
warm with highs in the upper 50s to lower 60s.

Inherited forecast looks on track given the benign weather pattern
and as such see no need for any morning updates at this time.

18

.LONG TERM /MONDAY THROUGH THURSDAY/...From Previous Discussion...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...Southwesterly flow aloft as an upper-level trough moves
southward into California. A mixed bag of ceilings this morning,
primarily MVFR with localized IFR at times with significant low
level moisture following the frontal passage last night. Shower
activity has largely ended, and conditions should stay dry through
the TAF period. Low ceilings should scatter out between 18-21Z,
leaving conditions VFR with mostly clear skies with high clouds
exiting this evening. Winds are northerly, increasing to 8-12 kt
today, easing a bit tonight. Some low stratus/fog may develop in the
most prone regions (PAE, PWT, HQM), but is not expected to be
widespread except along the Pacific coast.

KSEA...MVFR to IFR ceilings this morning, improving to VFR between
18-20Z this morning once low stratus evaporates. VFR conditions with
decreasing clouds for the remainder of the TAF period. Surface winds
northerly 8 to 12 kt through today, easing somewhat tonight.

LH

&&

.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. A Small Craft Advisory is in effect for the
coastal waters from 10-60 NM out. 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/LH

&&

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


&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 3 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.


&&

$$