368
FXUS66 KSEW 271009
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
305 AM PDT Fri Sep 27 2024

.SYNOPSIS...Zonal flow over Western Washington will quickly scour
out moisture this morning, paving the way for clearing skies this
afternoon. A broad ridge centered over the Rockies will keep
conditions dry and temperatures mild throughout the weekend. A
series of weak troughs will pass through during the start of next
week, but any precipitation should stay largely north of the area.

&&

.SHORT TERM /TODAY THROUGH SUNDAY/...Current satellite imagery shows
W WA socked in by mostly low level clouds in the wake of exiting
frontal system. Still seeing some occasional gusts up the Sound and
down the Strait, but speeds nowhere near where they were last night.
Latest radar shows some scattered weak bands of light precip with
some verification via ground obs...however some spots are reporting
this as only drizzle.

Latest models not really deviating from earlier solutions, with
zonal flow behind the exiting front expected to dry things out
pretty quickly today. Some lingering slight chance to low-end chance
PoPs still possible through mid-morning, however by afternoon precip
threat should be long gone and skies on their way to clearing.

The combination of a broad ridge centered over the Rockies and some
weak troughing off the coast of Canada will be enough to keep W WA
dry at least through Saturday. Even as this ridge shifts eastward
Sunday, the eastern pushing weak trough does not appear to sag
southward enough to bring any precip into the area. This will bring
an increase in clouds though.

Daytime highs throughout the short term period will remain mild,
generally in the lower to mid 60s for most locations, however some
spots in the southwest interior may sneak into the upper 60s.

18

.LONG TERM /MONDAY THROUGH THURSDAY/...Ridging over the eastern
Pacific will get next week off to a dry start Monday and even
extending into most of Tuesday. An upper level low sinking southward
from the Gulf of Alaska may bring a chance for rain the latter half
of Tuesday and much of Wednesday. Just like 24 hours ago however,
neither deterministic nor ensemble models are terribly impressed
with the chances or any potential amounts for much of the
CWA...except for possibly the northern third of the area. PoPs in
the forecast from the NBM still feel a little high, given that data.
More than likely, as stated yesterday, this output likely remains an
indicator of uncertainty as opposed to genuine PoPs.

Temps in the extended may cool slightly...but not
significantly...with most locations seeing highs in the upper 50s to
mid 60s.

18

&&

.AVIATION...Strong westerly flow aloft over Western Washington
today will ease and back to southwesterly late tonight into Saturday
as another weak upper trough approaches the region. The air mass
remains quite moist over the area this morning in the wake of a
frontal system that swept through the area overnight. Widespread IFR
or low MVFR ceilings can be expected this morning with isolated
light rain showers. Conditions will improve late morning through the
afternoon as the air mass gradually dries with weak upper ridging
rebuilding into the area. Locally gusty southerly surface winds will
ease this morning and the low level flow will become northerly this
afternoon into tonight.

KSEA...Low MVFR and tempo IFR ceilings are likely to persist through
18Z then gradually lift to predominantly VFR by around 21Z. Surface
winds southerly 7 to 11 knots this morning will veer north to
northwesterly this afternoon. The northerlies could be a little
gusty at times late this afternoon and evening with a few gusts of
in excess of 15 knots. 27

&&

.MARINE...A surface ridge will quickly build into the coastal and
offshore waters today in the wake of a deep surface low that swept
onshore near Haida Gwaii overnight. Surface ridging will build into
the interior of southern British Columbia by tonight turning the
flow northerly across area waters. Small craft advisories will
remain in place across the coastal waters and the west entrance to
the strait as hazardous double digit seas will continue before they
subside below 10 feet by Saturday night. A system passing mainly to
the north of the area Saturday night and Sunday will enhance onshore
flow with likely small craft advisory westerlies in the strait.
Otherwise, conditions will remain fairly tranquil across area waters
into early next week as high pressure remains in control.

27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 5 AM PDT Saturday for Coastal Waters
     From Cape Flattery To James Island Out 10 Nm-Coastal Waters
     From James Island To Point Grenville Out 10 Nm-Coastal
     Waters From Point Grenville To Cape Shoalwater Out 10 Nm-
     Grays Harbor Bar-West Entrance U.S. Waters Strait Of Juan
     De Fuca.

     Small Craft Advisory until 5 AM PDT early this morning for
     Northern Inland Waters Including The San Juan Islands-Puget
     Sound and Hood Canal.

     Small Craft Advisory until 3 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.

&&

$$