865
FXUS66 KSEW 191629
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
929 AM PDT Thu Sep 19 2024

.SYNOPSIS...Weak high pressure holds over the region through
Thursday with morning clouds but afternoon sunshine. Expect a
return to a wetter pattern Friday and again late in the weekend as
the next disturbance crosses the region.

&&

.SHORT TERM /TODAY THROUGH SATURDAY/...Forecast remains on track
with some lingering low clouds across parts of the area. These
will gradually scatter through the morning with increasing sun
this afternoon for most of the area. No updates this morning, and
the previous short/long term sections follow.       12

Western WA remains under the influence of onshore flow for
slightly cooler weather today - highs tracking a degree or two
below average. There is a disturbance rolling through southern
B.C. but we remain dry for the most part (aside from a few light
showers in the Cascades). A weak ripple may help generate a few
more showers in the interior and Cascades on Friday. The next
incoming frontal system pushes into B.C. and stalls as we move
into Saturday, keeping western WA mainly dry. The air mass will be
a little warmer with temps tracking closer to average. 33

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Wetter weather is ahead as
we move into later Sunday and Monday, especially for the coast and
mountains with a steady stream of moisture over the region.
Ensemble guidance is backing off on total rainfall amounts in the
interior (Seattle south) with a 25-50% chance of seeing
measurable rain. But there`s a good chance of wetting rains at the
coast and mountains with 0.25-0.50" ranges. Moving on, we`re on
the northern edge of a ridge as it moves inland on Tuesday. This
results in a dry and warmer pattern with highs in the 70s again.
Then, toward midweek, moist SW flow returns as the ridge moves
farther inland. This brings cooler and wetter weather back to
western WA with a chance of rain. 33

&&

.AVIATION...An upper ridge centered well offshore and an upper
trough moving into British Columbia today will produce increasing
northwesterly flow aloft over Western Washington. Widespread low
level moisture remains in place across the area this morning
producing a mixed bag of ceilings. Areas of IFR/MVFR ceilings/mist
and localized LIFR fog/clouds will continue this morning before
lifting to VFR across interior areas 18Z-20Z. Increasing low level
onshore flow later today is expected to spread low MVFR stratus
across much of the lowlands of Western Washington on Friday morning.
Winds will be variable between southwesterly (South Puget Sound) to
northwesterly elsewhere at 4 to 8 kt (highest winds towards the
coastline and Strait of Juan de Fuca).

KSEA...Still on the lookout for possible brief periods of low
stratus/fog this morning (but this has only filled in a couple of
times - however low stratus to the north of the terminal may sneak
in briefly mid morning before mixing/lifting upward). The risk of
low clouds/mist will diminish late this morning/afternoon by 19-20Z
as clouds scatter out. MVFR ceilings will fill back in as early as
12Z Friday for the morning. Winds will be variably out of the west 4
to 8 kt.  27/HPR

&&

.MARINE...Broad surface ridging will remain centered well offshore
into the weekend. Onshore flow will increase tonight into Friday as
a system moves by well to our north. Small craft advisories have
been posted for the outer coastal waters and the central/east
portions of the strait. Surface ridging expands in the coastal and
interior waters on Saturday for lighter winds. A series of weak
frontal systems will brush the area early in the coming week, but
are presently not expected to produce any headlines. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 5 PM this afternoon to 3 AM PDT Friday
     for Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 11 PM this evening to 5 PM PDT Friday
     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.

&&

$$