049
FXUS66 KSEW 110337
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
837 PM PDT Sun May 10 2026

.SYNOPSIS...
A weak system clipping the region has brought in an expansive
cumulus field with partly sunny skies. A warming trend is
expected through Tuesday. Thereafter, conditions become more
unsettled with a chance for isolated thunderstorms on Wednesday.
Cloudy and cooler conditions will persist through the end of the
week.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
A mix of partly cloudy skies to mostly cloudy skies across
Western Washington this evening. Light shower activity has
dwindled across much of the area. Any remaining showers are
expected to taper off tonight.

High pressure bumps back in early this week, with warming
temperatures through Tuesday. Tuesday looks to be on track for
the warmest temperatures this week, with widespread upper 70s to
mid 80s across the region. The warmest temperatures are
forecast to be in areas from south King County in through Mason
and Grays Harbor County. The Cascade valleys will also be well
into the 80s. These locations are giving a 50 to 70% chance of
reaching Moderate HeatRisk, which can impact the most sensitive
demographics-especially with limited access to cooling. Given
the pattern, minimum relative humidity values on Tuesday are
forecast to be between 25 to 30% in the Cascades and 35 to 40%
throughout much of Puget Sound. The winds, although light, seem
to be slightly northeasterly which could drive these RH
forecasts even lower. Overnight temperatures will be cool enough
to offset some of it being in the low to mid 50s. Relief will
be in short order as the pattern turns unsettled into the second
half of the week.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
The pattern becomes more unsettled Wednesday through the second
half of the week. A cutoff low offshore of the OR/CA border
amplifies and nudges the ridge off to the east. While the exact
track of that cutoff low is still carrying some uncertainty, it
does provide potentially favorable conditions for a few
thunderstorms Wednesday morning into early afternoon. Southerly
flow and an increase in CAPE could favor some orographically
enhanced storms in the southern WA Cascades and foothills. Right
now, it seems as though some of the ingredients are misaligned
with the generally necessary solar insolation of the day, but
this will be monitored as Wednesday approaches.

Broader troughing in the NE Pacific keeps onshore flow into
Washington for the rest of the week, allowing some weaker
systems to move in. Scattered showers could occur during this
timeframe but are unlikely to produce significant rains.

21

&&

.AVIATION...
West to southwest flow aloft will gradually become more west/
northwesterly on Monday as an upper level ridge moves back into
the region. The majority of the terminals are VFR this evening,
except for KHQM and KCLM which are MVFR in stratus. Some lingering
mid level cloud cover remains over the region in the wake of
some light shower activity this afternoon and the weak front
that moved across the area earlier. Otherwise, with an increase
of onshore flow tonight, expect stratus to push inland into
portions of the Southwest Interior and south/central Sound
late tonight into early Monday. This may yield some brief
periods of MVFR conditions for terminals across the central
Sound by early Monday. Expect conditions to improve mid-to late
morning for a return to VFR by the afternoon. Low-level onshore
winds expected to become lighter overnight before increasing to
8-12 kt out of the north on Monday afternoon.

KSEA...VFR this evening. However, areas of stratus are set to
redevelop this evening in moist onshore flow. The NBM has a 25-
30% chance of ceilings under 3,000 ft moving into the terminal
by early Monday. Should this occur, VFR conditions are set to
return by mid to late morning. Northerly surface winds will
persist between 3-6 kt overnight and will increase to 8-12 kt
between 18-21Z.

41/14

&&

.MARINE...
Post-frontal onshore flow will continue in the wake of a weak
front. A westerly push will continue to bring SCA-strength
winds through the Strait of Juan de Fuca through tonight. Winds
remain relatively light elsewhere and primarily out of the north.
A thermal trough will build along the coast on Tuesday, yielding
a brief period of offshore flow. A potential system approaching
the area midweek may bring another push through the Strait.
Additionally, while low stratus is expected off the coast the next
couple of mornings, there is potential for some pockets of fog
over the coastal waters (especially in areas where the wind is
calmer). Combined seas will hover around 4-6 ft through the week
(with a brief jump to 6-8 ft midweek).

41/14

&&

.HYDROLOGY...
The daily hydrology discussion has ended until the start of the
next rainy season; it will only be updated during this time as
needed.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 3 AM PDT Monday for Central U.S.
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
     Strait Of Juan De Fuca.

&&

$$