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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS66 KSEW 112037
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
137 PM PDT Thu Apr 11 2024

.SYNOPSIS...
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A weakening cold front will bring showers inland
throughout this afternoon and tonight across all of western
Washington. A weak ridge will clear out most clouds late Friday
afternoon into Saturday. High temperatures will max out in the
mid 60s on Saturday, with a couple areas in and around the
Southwest Interior potentially reaching 70. A series of systems
will return the chance of showers next work week.
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&&

.SHORT TERM /TONIGHT THROUGH SUNDAY/...
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Upper level analysis shows
a 300 mb trough positively tilted over the Pacific Ocean into
British Columbia/Alberta, with the center of the low off the coast
of Oregon/California. The low is expected to cutoff as it fills
over the Pacific, leaving western Washington in a zonal flow
pattern through the weekend (as the flow splits). At the surface,
a weakening cold front continues to approach the western
Washington coastline this afternoon.

A band of showers/light rain has been observed on radar moving
northeastward over the Pacific Ocean. As of early this afternoon,
showers have begun falling over the Olympics, and into Quillayute.
Coverage is expected to increase eastward this afternoon/evening
as the surface low pressure center tracks southward from British
Columbia, through Washington and into Oregon. The system is
expected to slow down coming onto land, which will keep
precipitation chances lingering through the first part of Friday.
Most of the rain will fall in the coastal areas/Olympics, with
potentially over half an inch of QPF possible. Remaining areas
will only see a tenth of two of an inch of QPF (though a possible
convergence zone over Snohomish County cannot be ruled out once
the front passes).

The remainder of this weekend looks dry with the zonal flow/weak
ridge setting up over Washington. Skies will gradually clear out
during the day Friday, and for most of Saturday. The warmest day
will be on Saturday, with widespread high temperatures in the mid
60s. A couple areas in the Southwest Interior may have a shot of
seeing 70 degrees (especially given the zonal flow). A few more
clouds will increase on Sunday as the zonal flow breaks down with
an approaching trough from the north. Temperatures outside of
Saturday will top out in the upper 50s to low 60s. Expect low
temperatures to drop into the 40s. Surface winds in this period will
remain light over land (around 5 mph), and will be out of the
southwest Thursday, and north Friday into Sunday.

.LONG TERM /MONDAY THROUGH THURSDAY/...Ensembles/deterministic
models have the zonal flow breaking down on Monday, with a trough
digging down into Washington through the first part of the work
week. This will keep a chance of showers Monday through the first
part of Wednesday. There`s split confidence as to what happens
post Wednesday, but there seems to be more models leaning towards
some clearing and ridging behind the trough. Sunday/Monday`s front
may be a little breezy, but otherwise no significant winds are
expected in the long-term. High temperatures will take a dip into
the mid 50s Monday/Tuesday, before climbing back to the low 60s
Wednesday/Thursday.

HPR
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&&

.AVIATION...
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Southwest flow aloft continues with weak frontal
boundary offshore expected to dissipate as it moves onshore this
evening. MVFR Ceilings in light rain along the coast will spread to
interior areas this evening.

KSEA...Ceilings will gradually lower to high end MVFR in light rain
by around 03Z as dissipating frontal boundary moves into the area.
MVFR ceilings then expected to remain in place through late morning
on Friday. Surface winds S/SW 5 to 10 knots will transition to
northerly after 09Z tonight and increase to 8 to 12 knots by early
Friday afternoon. 27
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&&

.MARINE...
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A weak front will slowly shift inland and dissipate
tonight. Broad surface ridging will expand over the offshore and
coastal waters Friday and Saturday. This will lead to increasing
northerlies...some of which are expected to reach small craft
advisory speeds over the outer coastal waters. A frontal boundary
sliding southward over British Columbia later Sunday will produce a
sharp increase in onshore flow. This will likely lead to additional
headlines in the form of small craft advisory level winds for the
coastal waters and possible westerly gales in the strait Sunday
night. Surface ridging gradually rebuilds across the waters early
next week for a transition to quieter conditions.

A sustained period of northwest winds over the coastal waters this
weekend into early next week is expected generate hazardous seas in
the form of short period swell at times. 27
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&&

.HYDROLOGY...
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River flooding is not expected over the next seven
days.
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&&

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

$$