934
FXUS66 KSEW 241055
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
355 AM PDT Fri May 24 2024

.SYNOPSIS...Cooler and unsettled conditions return today and will
persist into Saturday as an upper level trough moves across the
region. Upper level ridging then looks to build into the Interior
West early next week, however troughing over the northeastern
Pacific will continue and will bring additional chances of
precipitation across western Washington at times.

&&

.SHORT TERM /TODAY THROUGH SUNDAY/...Cooler and unsettled conditions
return today as the next upper level trough drops down into the
region from British Columbia. Radar this morning shows showers
moving inland along the coast ahead of a surface low and its
associated frontal system. Expect showers to continue to push
inland throughout the day and persist into Saturday. Onshore flow
will increase in the wake of the frontal system Friday night into
Saturday and high-resolution models continue to hint at a convergence
zone developing across the central Sound overnight into Saturday.
Overall, expect precipitation amounts to remain rather light as
this system moves across the region, with most lowland locations
looking to receive a tenth to a quarter of an inch. A few spots,
primarily in the vicinity of the convergence zone and across the
northern Sound, may see some higher rainfall amounts -most likely
towards half an inch in any heavier showers. Amounts across the
mountains are generally expected to be 0.50-1.25 inches through
Saturday. High temperatures today and Saturday will be below
normal, likely topping out in the mid to upper 50s for much of the
area.

Upper level ridging will start to build across the Interior West
on Sunday, however western Washington will continue to be
influenced from upper level troughing over the northeastern
Pacific. A warm front moving into British Columbia looks to brush
the region, likely bringing another round of showers to portions
of the coast and areas from Snohomish County northward. Areas
across the central and southern Sound look to remain drier and
afternoon highs look to warm a few degrees, generally topping out
in the upper 50s to low 60s. Highs along the coast will remain
cooler and look to remain in the 50s. Precipitation amounts
generally look to remain light, with most spots only looking to
receive a few hundredths of an inch of rain. The exception is the
Northern Coast, which could pick up 0.25 to 0.50 inches of rain.

.LONG TERM /MONDAY THROUGH THURSDAY/...Ensembles and deterministic
guidance are in good agreement that upper level ridging will
continue to build across the Interior West early next week.
Meanwhile, upper level troughing over the northeastern Pacific
will continue to influence western Washington and will keep shower
chances in the forecast, especially for portions of the coast and
Northern Interior. Precipitation chances then look to increase
Tuesday as another cold front moves across western Washington.
Uncertainty increases mid to late week as guidance continues to
struggle with the position of the upper level ridge and trough.
Have kept mention of slight chances of showers in the forecast for
now, though will have to see how guidance trends going forward.
High temperatures look to trend in the 60s.

&&

.AVIATION...Westerly flow aloft turning more northwesterly
through the day Friday with onshore flow at the surface. Some
lowering clouds from west to east ahead of an approaching front,
with a mix of MVFR and VFR conditions expected toward daybreak. Rain
pushing onshore 13-16z before slowly reaching Puget Sound toward 21z.


KSEA...Southerly surface winds and increasing clouds this morning.
Expect lower VFR ceilings giving way to MVFR conditions toward 16z.
Shower chances increase from 21z onward, with mostly MVFR conditions
and southerly winds continuing through the remainder of the period.

&&

.MARINE...An approaching front will bring increasing winds
and steep seas over the coastal waters later today. Expect the most
widespread advisory strength winds beyond 10 nm from shore, but
occasional gusts to 25 kt are possible into the inner waters.
Meanwhile, expect seas to build into the 7 to 10 ft range by tonight
with dominant periods generally 8 or 9 seconds. As a result, a small
craft advisory has been issued to cover the coastal waters. A modest
push down the Strait of Juan de Fuca this evening will be followed
by a stronger push of westerlies Saturday morning. This may need an
advisory with more solid winds expected. The next frontal system
will move into B.C. on Sunday with increasing southerly winds. Seas
over the coastal waters generally hold around 5 to 6 feet during the
early part of next week.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 7 PM this evening to 8 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.

     Small Craft Advisory from 2 PM this afternoon to 8 AM 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.

&&

$$