Forecast Discussion for SEW NWS Office
000
FXUS66 KSEW 190306
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
806 PM PDT Mon Mar 18 2024

.SYNOPSIS...Upper ridging will continue into Tuesday for dry,
warmer weather. A subtle trough will move through later Wednesday
into Thursday for increasing precipitation chances. Troughing will
develop further next weekend for cooler temperatures and
precipitation.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...Clear skies this
afternoon with temperatures generally ranging in the 60s for much
of the area. Another uptick in onshore flow tonight into Tuesday
will result in another period of low stratus or fog Tuesday
morning. Fog may be dense in areas during this period before
clearing late morning for additional sunshine. Temperatures on
Tuesday will be similar in the 60s, although cooler temperatures
likely along the coast due to the onshore flow.

The upper ridge will slowly begin to weaken on Wednesday with
subtle troughing sliding across western Washington. Precipitation
potential increases Wednesday, especially later in the day, and
continuing into Thursday. QPF amounts will generally be light for
most areas, heaviest in the Cascades. Snow levels will range
4000-5000 feet Wednesday through Thursday. Temperatures will fall
to near normal Wednesday into Thursday with highs in the low to
mid 50s.

.LONG TERM /FRIDAY THROUGH MONDAY/...An upper low will move
towards OR/CA on Friday with continued weakening ridging across
the interior West. This upper low will result in continued
precipitation chances Friday into Saturday. Uncertainty increases
in ensemble guidance in regards to the track of the upper low, but
a consistent pattern is noted with further troughing developing
over the Pacific Northwest. Cooler temperatures are expected along
with continued precipitation chances into early next week across
the area. JD

&&

.AVIATION...An upper-level ridge of high pressure will continue to
shift off to our south and east with southwest flow aloft. Light
onshore flow at HQM and CLM with northerly flow at the Puget Sound
terminals, turning light and variable by 06Z tonight. This will set
the stage for another round of LIFR/IFR stratus and patchy fog late
tonight into Tuesday morning. Best chances for VSBY and CIG
restrictions will be between 09-16Z Tuesday (30-40% chance for IFR
or lower).

KSEA...VFR through early tonight with light northerly winds 5-10 kt
shifting to the east-northeast after 02Z. Lighter surface flow
tonight with the ridge shifting east of the region increases the
chance for CIG/VSBY restrictions with a moderate (40%) chance for
IFR or lower CIGs in fog and low stratus. Northeast winds shift to
the west-southwest Tuesday morning 5-10 kt.

Davis

&&

.MARINE...Onshore flow pattern continues with weak surface troughing
along the coast Tuesday into Wednesday and sub-advisory conditions,
aside from brief wind gusts to near 20 kt across the far southern
waters of the Strait of Georgia tonight. Seas less than 10 feet
through the week. A splitting frontal system looks to move across
the area waters Friday with the next main chances for advisory-
strength winds Friday into Saturday.

Davis

&&

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

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&

$$

NWS SEW Office Area Forecast Discussion