927
FXUS66 KPQR 090440
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
940 PM PDT Tue Jul 8 2025

.UPDATE...Quick update this evening. A strong southwest to
westerly marine push is underway. The KOTH-KPDX pressure
gradient peaked at over 7mb this evening, which is up there.
Typically, when this gets to 5mb, we are in for a solid
southwest marine push. Given Coast Range gap winds have been
blowing 10-20 kt for much of the evening at KEUG, KCVO and KMMV,
marine air is infiltrating the Willamette Valley and a
significant, albeit short lived change is underway. Have the
kept the current sky cover and temperature forecast as is, but
would suspect it will be substantially cloudier in the morning
than the current deterministic forecast suggests given the
observed pressure gradients and surface wind observations. As
such, would also expect that the current temperature forecast is
too high, potentially by quite a bit depending on how far and
quickly marine clouds push inland overnight. Given the typically
reliable HREF guidance is not bullish on cloud cover and little
model guidance suggests a drastically cooler temperature
forecast, going to forego making any drastic changes, will
leave the grids alone this evening and let the night shift
monitor trends and adjust as necessary.

In addition, some elevated instability and large scale lift
ahead of an approaching shortwave trough triggered a lone
thunderstorm over Clackamas County that died quickly and is now
moving over the west-central Columbia River Gorge before it will
shift northeastward towards Mt Adams over the next 1-2 hours.
Cannot rule out another isolated cell, but overall this threat
should be coming to an end across our CWA with the focusing
generally remaining east and northeast of our CWA overnight.

Meanwhile, a weakening cold front will push into southwest
Washington and northwest Oregon Wednesday. NBM PoPs have come
down a little bit from earlier, which given the current
lackluster amount of radar returns across the Olympic Peninsula
and points west does not seem unreasonable. Nonetheless, these
shallow fronts have a tendency to overperform and wring out a
surprising amount of drizzle so will keep NBM PoPs as is for
Wednesday morning. /Neuman



&&

.SYNOPSIS...
Inland highs around 90 degrees again this afternoon.
A weak frontal system brings more seasonable temperatures for
Wednesday and Thursday, with a chance for some light rain along
northern coastal areas early Wednesday. Hotter temperatures
return Friday and persist into next week as strong high pressure
builds offshore.

&&

.SHORT TERM...Now through Thursday Night...
Now through Thursday Night...High pressure remains
entrenched over the western CONUS today, promoting clear skies
across all of western Oregon and Washington with the exception
of some patchy marine stratus along the immediate coast.
Observations from around the area show highs in the upper 80s to
low 90s in the interior valleys as of mid afternoon. Visible
satellite shows cumulus fields starting to become more agitated
near and east of the Cascade crest in central Oregon, and expect
this to eventually yield a few thunderstorms this afternoon and
evening as cutoff upper level low pressure drifts inland from
northern California. Expect most of this activity to remain on
the east side of the Cascades, but will maintain a 15-20% chance
of thunderstorms along the Lane County Cascades this evening as
a few storms could move near the Crest later today.

A brief pattern change will commence tonight as a deep upper
level trough over the Gulf of Alaska pushes inland across
western Canada. This will send a weak surface cold front across
the Pacific northwest early Wednesday, bringing about cloudier
weather and more seasonable temps for the area Wednesday into
Thursday. Expect any precipitation chances to remain limited to
northern coastal areas and parts of southwest Washington on
Wednesday. Model QPF suggests parts of Pacific County could see
as much as a tenth or two of an inch of rain through early
Wednesday afternoon, but other locations along the north Oregon
Coast or the Cowlitz Valley will likely be limited to a trace
to a few hundredths. Although other locations are expected to
remain dry, passage of the front will at least bring some
temporary relief from the recent hot temperatures as afternoon
highs will run about 10 degrees cooler in the interior valleys,
maxing out in the upper 70s to around 80 degrees in most
locations. Expect dry weather on Thursday, with a bit less cloud
cover and temperatures rebounding by a few degrees into the low
80s in many interior locations. Meanwhile, persistent onshore
flow amd marine stratus will keep coastal temperatures in the
low to mid 60s going forward. /CB

.LONG TERM...Friday through Tuesday...Hotter temperatures return
on Friday and look to persist well into next week as ensemble
clusters remain in lock step in depicting a strong upper level
ridge developing across the NE Pacific in the long term. This
will likely correspond to a prolonged stretch of daytime highs
in the low 90s across the Willamette Valley and Portland
Vancouver Metro, helping to maintain a moderate Heat Risk in
these areas from Friday into next week. The probability to reach
95 degrees ranges from 60-80% from Salem to Eugene and 25-40%
in the Portland/Vancouver Metro each day from Friday through
Monday. The NBM is hinting at the possibility for even hotter
temperatures next Tuesday and Wednesday, with NBM 75th
percentile guidance depicting highs reaching the low 100s from
the Portland/Vancouver Metro to Eugene and pushing Heat Risk
into the Major category on Tuesday. It should be said that more
modest highs in the low 90s remain well within the range of
outcomes on these days, but the potential is there for the first
widespread triple digit readings of the summer as we head into
Tuesday and the middle of next week.

In terms of precipitation, certainly expect most of the area to
remain dry through the end of the long term. However, did note
that most deterministic solutions depict a mid level impulse off
of northern California this weekend and early next week, which
maintains at least a thought for a few thunderstorms in the
vicinity of the Lane County Cascades into the long term. Model
probabilities are too low to warrant inclusion of thunderstorms
in the forecast for now, but will need to monitor this potential
as models start to better resolve this feature in the coming
days. /CB




&&

.AVIATION...Weakening high pressure over the region will
give way to a dying front sliding into northwest Oregon and
southwest Washington Wednesday morning. Marine clouds are
pushing into the Coast Range gaps as a strong southwest to west
marine push is underway with the KOTH-KPDX gradient peaking at
over 7mb earlier this evening. This suggests marine clouds
should deepen substantially overnight and push into the
Willamette Valley despite most high resolution model guidance
suggesting otherwise. At the moment, high resolution ensemble
guidance suggests a 50% chance that marine clouds reach KEUG and
stay primarily downriver of KPDX & KTTD along the lowest
stretches of the Columbia River. Given the solid 10-20 kt sea
breeze observed most of the evening at KEUG, KCVO, KS12 and
KMMV, and the aforementioned observed pressure gradients, have
hedged towards MVFR ceilings being more likely than not with the
latest TAF package for inland taf sites Wednesday morning. The
aforementioned dying front will push onto our northern coastal
zones around daybreak on Wednesday with a 50-60% chance for
drizzle and light rain at KAST between 12-20z Wednesday. The
odds the front hangs on enough to produce measurable drizzle or
light rain and impact visibilities for the Portland metro taf
sites has lowered to ~10% and drops to well below 10% as one
goes southward in the Willamette Valley.

PDX AND APPROACHES...Weakening high pressure over the region will
give way to a dying front sliding into northwest Oregon and
southwest Washington Wednesday. Marine clouds are pushing into
the Coast Range gaps this evening as a strong southwest to west
marine push is underway with the KOTH-KPDX gradient peaking at
over 7mb this evening. This suggests marine clouds should
deepen substantially overnight and push into the Willamette
Valley despite most high resolution model guidance suggesting
otherwise. Given the solid 10-20 kt sea breeze observed most of
the evening at KEUG, KCVO, KS12 and KMMV currently, and the
aforementioned pressure gradient, have hedged towards MVFR
ceilings arriving between 12-15z Wednesday for the Portland taf
sites. The aforementioned dying front will push towards the taf
sites between 15-20z Wednesday, but the odds the front is
strong enough to wring out measurable drizzle or light rain and
impact visibilities for the Portland metro taf sites is ~10%.
/Neuman

&&

.MARINE...A dense fog advisory has been issued to account for the
fact that the widespread low clouds over the waters are most
likely lowering to the ocean`s surface in the vicinity of the
maximum upwelling, which is typically within 20-30NM of the coast.
In addition, a weak front is currently dropping southeastward
into the waters. This will turn the winds southerly across the
waters overnight. Winds will be strongest within 20 NM of the
coast, particularly from Cape Falcon northward, but there is a 75%
chance that southerly wind gusts remain below 20 kt. Once the
front passes, winds will turn west to northwesterly late in the
day on Wednesday.

We will then return a more typical northerly wind pattern Thursday
into Friday as high pressure builds across the northeast Pacific
and thermally induced lower pressure returns to northern
California. This will produce gusty northerly winds and choppier
wind driven seas, particularly south of Cape Falcon. Winds and
seas will be strongest off the central coast of Oregon and will
typically peak in the afternoon and evening hours over the inner
waters each day through the weekend. /Neuman

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Dense Fog Advisory until 11 AM PDT Wednesday for PZZ210-
     251>253-271>273.
&&

$$

www.weather.gov/portland

Interact with us via social media:
www.facebook.com/NWSPortland
x.com/NWSPortland