171
FXUS66 KSEW 241600
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
900 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/...No significant change to the
forecast this morning. The previous discussion can be found below
along with updated aviation and marine sections:

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...Moist, westerly flow aloft today with a trough
overhead. Expect low level moisture increasing throughout the
region for scattered showers and MVFR conditions. Moisture lingers
tonight with showers mainly in the interior and Cascades as the
trough exits. 33

KSEA...Trend is toward lowering ceilings this morning and
afternoon for MVFR conditions. S winds around 10 kt with showers
in the vicinity. Little change overnight. 33

&&

.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.

&&

$$