544
FXUS66 KSEW 140309
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
808 PM PDT Sun Jul 13 2025
.SYNOPSIS...A brief reprieve in warm temperatures is expected on
Monday as a system slides southward from British Columbia and
skirts the area. Warmer and drier conditions will return Tuesday
through Thursday, with some lowland locations potentially seeing
highs in the 90s by Wednesday. Elevated fire weather conditions
are also expected during this warm up. A cooling trend then
commences late in the week and into next weekend.
&&
.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...A northwesterly
oriented onshore push in underway this evening with the UIL/BLI
gradient now approaching 4 millibars with gale westerlies in the
strait. The upper trough responsible for this is digging
southeastward across British Columbia this evening. Apart from
cooler temperatures and morning cloud cover on Monday, there won`t
be much in the way of impacts for the CWA with precip of any
consequence staying well north of the border. A rapid warming trend
for Tuesday and Wednesday is still on track. Given recent
performance, high temperatures for midweek may run closer to the NBM
75th percentile or higher which gives Seattle and points southward a
a shot at back-to-back 90 degree days. Current forecasts run closer
to the 50th percentile, but watch this space for updates as we get
closer to the next warm spell. Previous discussion follows with
updates to the marine and aviation portions.
Warm and dry conditions continue across the area this afternoon with
temperatures generally ranging in the 80s to low 90s across the
interior. Areas along the coast remain much cooler, with
temperatures ranging in the 60s to low 70s under onshore flow and
with stratus still present along the coast.
A brief reprieve in temperatures is expected on Monday as a positively
tilted trough slides down across British Columbia and skirts
western Washington. Outside of a slight chance of showers across
the far Northern Cascades, the main impact from this system will
be cooler temperatures, an increase in cloud cover, and an
increase in onshore flow in the low levels. High temperatures on
Monday will primarily be in the 70s to low 80s across the interior
and in the 60s along the coast.
Conditions start to ramp up again on Tuesday as high pressure
offshore starts to build into the region and a thermal trough at
the surface builds northward into the area. Afternoon highs on
Tuesday will rebound into the 80s for the majority of the interior
lowlands, with temperatures along the coast expected to climb
into the 70s to low 80s. Temperatures will continue to warm and
will peak on Wednesday, with highs expected to be in the 80s to
low 90s across the interior. With overnight lows generally
expected to be in the upper 50s to low 60s, this will bring
another round of Moderate HeatRisk to the majority of the interior
lowlands. This warm and dry trend will also bring elevated to
critical fire weather conditions to portions of the area both
Tuesday and Wednesday. More details on fire weather can be found
below in the fire weather section.
.LONG TERM /THURSDAY THROUGH SUNDAY/...Ensembles continue to have a
tough time converging on solutions late in the week. At this time,
Thursday looks to remain warm for much of the area outside of the
coast, however there remains a decent spread in temperatures
amongst the ensemble members. Guidance starts to show more of a
cooling trend by Friday with an increase in onshore flow, though
highs are still expected to be above normal and in the 80s for
the interior lowlands. At this time, temperatures look to cool
closer to seasonal norms over the weekend. 14
&&
.AVIATION...West-northwest flow aloft as upper-ridging continues
offshore. Widespread VFR for majority of W WA this evening, although
marine stratus may impact coastal locations given proximity. As of
this writing /1930 PDT/, it has not pushed eastward enough to impact
HQM. Stronger easterly push overnight will result in widespread MVFR
conditions by 12-14Z Monday morning and persisting before conditions
start to improve early Monday afternoon. VFR conditions resume
afterward, save for HQM, which may still be affected by lingering
marine stratus.
Northerly surface winds through the interior this evening with
speeds 8 to 12 kt, easing overnight to generally 4 to 8 kts. KCLM
seeing more westerly winds 10 to 15 knots this evening with gusts
ranging 20 to 25 kts possible. Winds here may ease slightly
overnight to 8 to 12 kts.
KSEA...VFR this evening but stratus is favored to return around 12Z,
with MVFR expected afterward. Cigs recover to VFR by 18-20Z. NW
winds this evening 8-12 kts, with the potential of some gusts up to
20 kts. Northerly winds easing to 4-8 kts by 06Z, remaining there
for the rest of the TAF period.
McMillian/18
&&
.MARINE...Surface high pressure remains offshore with onshore flow
throughout the area waters. Diurnally driven westerly pushes down
the strait will continue over the next several days of differing
magnitude. Latest guidance has shown more strength in the westerly
push tonight, therefore a Gale Warning remains in effect for the
Central and Eastern Strait. Northerly winds also look to increase
over the coastal waters this evening along with steep seas, so A
Small Craft Advisory also remains in effect well into Monday.
Thermal troughing looks to build along the coast through midweek,
with periodic increases of northerly winds through the area waters.
Combined seas 6 to 8 feet look to increase to 8 to 10 feet by Monday
morning. Seas will likely remain elevated throughout the first half
of the week.
McMillian/18
&&
.FIRE WEATHER...A passing disturbance Monday will bring a brief
relief from the very warm and dry conditions of the weekend. This
system will bring much stronger onshore flow, spreading widespread
clouds and cooler conditions. However, attention will then turn to
the return of high pressure over the region. Expect to see afternoon
RH values dip down close to critical thresholds Tuesday afternoon
with a thermal trough building north over the Cascades. While some
uncertainty remains with respect to how far north and west this
builds, expect to see at least some east component to the surface
winds near the Cascade gaps in zone 659 and perhaps portions of 657
and 658. Confidence is lower in seeing more widespread easterly wind
and speeds may not be strong enough to raise fire weather concerns
to critical, but this may serve to further reduce RHs. Additionally,
depending on the placement of the thermal trough, expect to see a
deeper mixed layer and increased instability with mixing heights
potentially rising into Wednesday. While confidence in the specific
timing of elevated fire weather concerns is still lower, the mid
week period bears close watching for both existing incidents and for
the potential for conditions to remain of concern if new ones were
to begin. Looking ahead to the end of the week, expect conditions to
remain warmer and drier than normal but forecast guidance continues
to exhibit a large range of potential scenarios that leave
confidence lower than normal. Cullen
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Gale Warning until 6 AM PDT Monday for Central U.S. Waters
Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of
Juan De Fuca.
Small Craft Advisory until 5 AM PDT Monday for Admiralty Inlet.
Small Craft Advisory until 7 AM PDT Monday for Coastal Waters
From Cape Flattery To James Island 10 To 60 Nm-Coastal
Waters From Cape Flattery To James Island Out 10 Nm-Coastal
Waters From James Island To Point Grenville 10 To 60 Nm-
Coastal Waters From James Island To Point Grenville Out 10
Nm-Coastal Waters From Point Grenville To Cape Shoalwater
10 To 60 Nm-Coastal Waters From Point Grenville To Cape
Shoalwater Out 10 Nm.
&&
$$