895
FXUS66 KSEW 111052
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
352 AM PDT Sat May 11 2024

.SYNOPSIS...Upper level ridge over the area today will weaken
tonight and Sunday. Upper level trough moving through Sunday night
with a weak upper level disturbance Monday. Another upper level
ridge moves through Western Washington Tuesday. Possible unsettled
weather Wednesday into Friday.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...What a show! That had to be
the best aurora visible in the Seattle earlier this morning.
Satellite imagery shows clear skies over Western Washington.
Surface gradients have gone flat with light winds being reporting
in most locations. Temperatures at 3 am/10z are mostly in the
upper 40s and 50s with Seattle and Everett still in the lower 60s.

Upper level ridge over the area today starting to weaken this
afternoon. Surface gradients remain light this morning before becoming
onshore this afternoon. The transition to onshore flow will result
in much cooler temperatures along the coast with highs mostly in
the 60s. Interior high temperatures a little tougher to forecast.
Temperatures aloft cooling slightly with the weakening ridge. Onshore
flow in the afternoon will put the breaks on the daytime heating
but temperatures this morning are 3 to 6 degrees warmer than
yesterday. End result is high temperatures near what they were on
Friday with just a couple of degrees of cooling, 70s to lower 80s.

Upper level ridge continuing to weaken tonight with increasing
onshore flow. Stratus along the coast spreading inland but still
looks like most of the stratus will stay west of Puget Sound. Lows
tonight in the upper 40s to mid 50s.

Upper level trough offshore approaching the coast but remaining
offshore Sunday. Low level onshore flow continuing throughout the
day giving the interior a good 10 to 15 degrees of cooling. Highs
along the coast will be in the lower to mid 60s. For the interior
mid 60s to lower 70s.

Upper level trough moving through Sunday night. Weak upper level
shortwave embedded in the northwesterly flow aloft arriving
Monday. Not much in the way of dynamics with both of these
features. The shortwave could set off some light showers in the
Cascades Monday. Lows Sunday night in the upper 40s to mid 50s.
Highs continuing to cool over the interior with upper 50s to mid
60s forecast for the entire area.

.LONG TERM /TUESDAY THROUGH FRIDAY/...Models in good agreement for
Tuesday with a brief upper level ridge rebuilding over the area
for a dry and slightly warmer day. Once again confidence is low
for Wednesday through Friday with the models very inconsistent in
their solutions. The operational ECMWF brings a weak front into
the area Wednesday followed by an upper level trough Thursday that
moves out of the area Friday. The operational GFS has an upper
level ridge over Western Washington Wednesday weakening Thursday
with an upper level trough arriving Friday. The GFS ensembles are
dry through the period while the ECMWF ensembles have about half
of the solutions being wet from Wednesday night through Friday.
Forecast for now is a broadbrush mostly cloudy with a slight
chance of showers Wednesday night through Friday with high
temperatures trending slightly above normal. Felton

&&

.AVIATION...An upper ridge remains in control with westerly flow
aloft. The air mass is dry and stable. Low level onshore flow will
increase today as thermally induced low pressure shifts into the
interior of Western Washington. This will bring IFR ceilings in
stratus to coastal areas tonight, but VFR conditions will prevail
elsewhere.

KSEA...VFR. Surface winds light and variable wind becoming W/NW less
than 10 knots this afternoon and evening. 27

&&

.MARINE...Thermally induced low pressure shifts into the
interior of Western Washington today then east of the Cascades
tonight and Sunday. This will lead to increasing onshore flow. A
weak system will pass to the north of the area Sunday night and
Monday. Small craft advisory conditions will develop over the
coastal waters today and continue through the weekend. A westerly
push in the strait will develop later today, but a stronger push on
Sunday could produce gales in the central/east strait.

Onshore flow will prevail through much of early next week for
periodic small craft advisory winds across the coastal waters as
well as the strait.

27

&&

.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 4 PM this afternoon to 3 AM PDT Sunday
     for Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca.

     Gale Watch from Sunday morning through Monday morning for
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance
     U.S. Waters Strait Of Juan De Fuca.

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

     Small Craft Advisory until 3 AM PDT Monday 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.

&&

$$