031
FXUS66 KSEW 120252
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
752 PM PDT Sat May 11 2024

.SYNOPSIS...Mostly clear skies will prevail tonight, but upper
level ridging will start to weaken into Sunday. A weak system
will move across the area Sunday night into Monday with a touch
cooler temperatures with conditions staying mostly dry. High
pressure looks to build back into the area Tuesday into Thursday
with warm conditions. Unsettled weather looks to make a return by
the weekend.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...Latest satellite
imagery shows another beautiful day across western Washington.
Upper level ridging will start to weaken over our area into
Sunday, with high temperatures in the interior this afternoon
topping out to generally around 80 degrees. The transition to
onshore flow this afternoon will help the coastal locations cool
down, with high temperatures there this afternoon to be in the low
to mid 60s.

As the upper level ridge weakens tonight, skies will remain mostly
clear throughout most of the interior, with the possibility for
some patchy stratus along the coast. It will be another good
night for viewing conditions for the Aurora Borealis, especially for
interior locations. Refer to spaceweather.gov for more space
weather information, including tonight potential for viewing.

The aforementioned ridge will start to move eastward on Sunday and
flatten, weakening the thermal trough along the coast. This will
likely lead to slightly cooler temperatures across the area
tomorrow, along with increasing onshore flow, afternoon high
temperatures can be expected to generally be around the low to mid
70s.

A weak system will cross into our area Sunday night into Monday,
bringing a chance of showers across most of the region, with the
most likely areas to receive any precip would be the Olympics and
the Cascades. Increased cloud cover on Monday will bring temps
down to around normal, in the mid 60s. High pressure looks to
rebuild back in the area on Tuesday, for slightly warmer temps
in the low 70s for the interior, and mid 60s for the coast.

.LONG TERM /THURSDAY THROUGH SUNDAY/...Ensemble guidance in
good agreement for a high pressure to build through Wednesday for
dry and warm conditions, with high temperatures not warming up
too much, staying in the low to mid 70s. Confidence is still
somewhat low looking at the end of next week, with the ECMWF
ensemble highlighting and unsettled pattern Friday and into
Saturday which would bring increased precipitation chances -
meanwhile, the GFS ensemble decides it wants another weekend or
dry and warm conditions over western Washington. Cluster analysis
also favors the ECMWF solution a bit which would bring unsettled
weather into next weekend, but nonetheless, temperatures look to
remain around seasonal normals, but could change if ridging does
develop.

Mazurkiewicz

&&

.AVIATION...An upper ridge remains in control with westerly flow
aloft, but weakens today. Low level onshore flow will increase today
as thermally induced low pressure shifts eastward, with a passing
upper level disturbance allowing for the return of some IFR ceilings
to return to the coastal areas. Not a sufficiently strong push to
reach into much of the interior with continued VFR conditions under
clear skies for most terminals.

KSEA...Northerly winds around 7-9 kt through evening with VFR
conditions under mostly clear skies. Any inland push of stratus
likely too weak to bring much into to south Sound or closer to the
terminal area - around than a 15% chance at best. Winds likely a bit
variable as they go light overnight, but predominantly northwest
winds expected Sunday once winds increase mid-morning onward.
Cullen

&&

.MARINE...A surface thermal trough has now moved east of the
Cascades, ushering in an increase in onshore flow with winds
currently beginning to pick up over the area waters. The strongest
winds (that is, most consistently around 20-25 kt) will remain over
the outer coastal waters, but with frequent gusts to 25 kt over all
of the coastal zones, as well as in the Central and Eastern Strait
of Juan de Fuca, the Small Craft Advisories will continue through
tomorrow evening. With a weak frontal system dropping north of the
area Sunday night and Monday, expect the onshore flow to further
increase. Have upgraded the Gale Watch to a warning for the Central
and East Strait of Juan de Fuca for late Sunday as a result.
Additional frontal systems will continue to cross the waters through
much of next week, with winds periodically building to near advisory
thresholds.

Seas are currently rather choppy, around 6 ft at 7 s, for which the
Small Craft Advisory also encompasses. Seas will build a bit with
each passing system to 7 to 9 ft, with periods remaining short,
around 7 to 9 seconds, through the middle of next week.

Cullen/LH

&&

.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 until 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 Warning from 2 PM Sunday to 4 AM PDT Monday for Central
     U.S. Waters Strait Of Juan De Fuca-East Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 11 PM PDT Sunday for Coastal Waters
     From Cape Flattery To James Island 10 To 60 Nm-Coastal
     Waters From Cape Flattery To James Island Out 10 Nm-Coastal
     Waters From James Island To Point Grenville 10 To 60 Nm-
     Coastal Waters From James Island To Point Grenville Out 10
     Nm-Coastal Waters From Point Grenville To Cape Shoalwater
     10 To 60 Nm-Coastal Waters From Point Grenville To Cape
     Shoalwater Out 10 Nm.

&&

$$