381
FXUS66 KSEW 180939
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
239 AM PDT Wed Sep 18 2024

.SYNOPSIS...Troughing remains over the region today with cooler
weather continuing. Weak high pressure brings a break in the
weather on Thursday. Expect wetter weather over the weekend as the
next upper level disturbance rolls through.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...Showers shifting south today
as a trough digs over the West. Onshore flow prevails across
western WA with plenty of low clouds over the lowlands. High
pressure tries to nudge inland this afternoon with a few sunbreaks
possible. Temperatures remain a few degrees cooler than average
and in the 60s.

Thursday`s weather looks dry but we`re still under the influence
of NW onshore flow for partly to mostly cloudy skies. The interior
may see a few showers on Friday where there`s convergence. Highs
in the 60s both days with lows in the 40s and 50s. 33

.LONG TERM /SATURDAY THROUGH TUESDAY/...There`s more wet weather
heading into the weekend with W to NW flow aloft, especially by
Sunday. By then, the next disturbance will roll through western WA
with rain spreading through the region. Wetting rains expected in
the mountains. Moving forward, high pressure shifts inland,
deflecting precip to the north or near the Canadian border.
Temperatures rebound with highs reaching the 70s again. 33

&&

.AVIATION...North to northwest flow aloft will increase over
Western Washington today as upper level ridging gradually rebuilds
into the region behind a departing trough. Low level moisture
remains in place with widespread IFR or low MVFR ceilings. With
light low level flow, these conditions will be slow to improve.
Ceilings will gradually lift to VFR away from the coast 21Z-00Z.
Continued relatively light surface flow favors the redevelopment of
IFR or low MVFR conditions in stratus/fog across the lowlands of
Western Washington again on Thursday morning.

KSEA...IFR ceilings in stratus will gradually lift to MVFR around
19Z or 20Z before becoming lower end VFR 22Z-00Z. Ceilings are
likely to sink down again tonight with low MVFR or tempo IFR
expected by daybreak Thursday. Surface winds light and variable
early becoming north/northwesterly 5 to 7 knots this afternoon. 27

&&

.MARINE...A weak surface low over the southern Oregon coastal waters
will continue to shift southward today as a broad surface ridge
centered well offshore expands into the Washington coastal waters. A
weak surface trough in the vicinity of Vancouver Island later
Thursday into Friday will likely tighten the northwesterly gradient
enough to produce some small craft advisory conditions over the
outer coastal waters in the form of gusty winds and steep seas.
Otherwise, relatively tranquil conditions are expected across the
remainder of area waters heading into the upcoming weekend. 27

&&

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

$$