839
FXUS66 KSEW 220835
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
135 AM PDT Wed May 22 2024

.SYNOPSIS...Showers will decrease today as an area of low pressure
over the region moves eastward. Weak high pressure aloft will
produce drier and somewhat warmer conditions on Thursday before
another upper level trough drops into Western Washington Friday
into Saturday for cool and unsettled conditions. A weak ridge of
high pressure will lead to milder temperatures early next week,
but will not prevent a chance of showers from remaining in the
forecast.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...Convergence zone activity
continues over Snohomish and north King counties early this
morning as moderate onshore flow remains in place in the wake of a
cold front that moved across the area early yesterday evening.
The trailing upper trough axis will slip east of the Cascades by
late this morning and low level onshore gradients will ease
allowing shower activity to dissipate by afternoon. Except for a
chance of evening showers in the Cascades, drier conditions will
develop tonight as northerly flow aloft develops once again ahead
of weak ridging offshore. A flattening ridge axis will slide
onshore on Thursday for mainly dry weather and a very modest
warming trend. The next in a seemingly endless series of upper
troughs slides southward from British Columbia on Friday for an
increasing chance of showers and cooler temperatures.

.LONG TERM /SATURDAY THROUGH TUESDAY/...The aforementioned trough
progresses southeastward across the area Friday night into
Saturday keeping the threat of showers in the forecast and
temperatures below normal. A subtle shift in the synoptic pattern
begins early next week as upper ridging builds across the Great
Basin and Intermountain West while a broad upper trough deepens
over the Gulf of Alaska. The proximity of the ridge should
contribute to somewhat warmer temperatures Monday into Tuesday,
but a sequence of systems brushing the region moving into British
Columbia will likely keep precip chances in the
forecast...especially over the Olympic Peninsula and North
Interior portions of the CWA. 27

&&

.AVIATION...Mainly MVFR to IFR with low stratus overspreading much of
the area early this morning. Convergence showers impacting KPAE will
slowly shift eastward before another round of showers pushes into the
area under northwest flow aloft. Brief improvement to low-end VFR early
this morning will likely be short-lived, with ceilings filling in
through the early afternoon. Conditions will improve heading into the
evening, returning to VFR across most of the terminals. The marine
layer will keep the coast in low ceilings through early Thursday.

KSEA...MVFR ceilings behind a cold frontal passage will continue
through the morning with southwest surface winds 10-15 kt with gusts as
high as 30 kt slowly easing to below 10 kt by the afternoon. VFR
conditions return by the early afternoon as cloud cover decreases.
Forecast models show a brief shift to north/variable flow between 20z-
00z before southwest flow returns, but confidence is low on the exact
timing and direction.

AL

&&

.MARINE...Strong post-frontal winds will continue throughout the
morning and into the afternoon before easing, with a Gale Warning for
portions of the outer waters and Small Craft Advisories for the rest of
the seas. Alongside the strong winds, seas will rise to 12 to 16 ft
offshore especially over the northern coastal zones throughout the
morning before the NW swell shifts southward. Waves will be steep with
short period waves dominating. Conditions will calm tonight into
Thursday before another frontal system passes through area waters on
Friday. This will likely bring another round of elevated seas and
breezy winds.

AL


&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 5 PM PDT this afternoon 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.

     Small Craft Advisory until 5 AM PDT early this morning for
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance
     U.S. Waters Strait Of Juan De Fuca-West Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Gale Warning until 11 AM PDT this morning 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.

     Small Craft Advisory from 11 AM this morning to 5 PM PDT this
     afternoon 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.

     Small Craft Advisory until 8 PM PDT this evening for Coastal
     Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm.

&&

$$