259
FXUS66 KPQR 121724 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1024 AM PDT Sat Jul 12 2025

Updated Aviation discussion.

.SYNOPSIS...High pressure maintains warm and dry conditions
this weekend, with a Heat Advisory on Sunday for most interior
valleys. Expect sunny skies across the area with morning marine
stratus/fog along the coast. Temperatures cool slightly on
Monday, but still remain warm and dry. An Extreme Heat Watch
continues for some interior valley locations from Tuesday to
Wednesday, as afternoon temperatures between 90 to 100 degrees
and low temperatures between 65 and 70 degrees are possible.

&&

.SHORT TERM...Now through Sunday night...Today`s conditions are
expected to be similar to yesterday with high pressure over the
northeast Pacific remaining in control. Marine stratus and fog
will impact the coast through much of the morning before
dissipating before noon. North winds are expected to increase
this afternoon, supporting gusts to around 20 mph inland and 25
mph along the coast and through the Columbia River Gorge. Highs
are expected to top out in the upper 80s to low 90s inland and
mid 60s to low 70s along the coast.

Sunday temps are forecast to jump up a few degrees  from Saturday as
the upper ridge persists and the overall airmass continues to warm-
up. 850 mb temperatures are expected to increase to 20-23 C and will
mix down to the surface on Sunday, leading to high temperatures in
the mid to upper 90s for interior valleys. Expect widespread
Moderate HeatRisk, which means that this level of heat affects most
individuals sensitive heat, especially those without effective
cooling and/or adequate hydration. A Heat Advisory is in effect
across the Willamette Valley, Portland/Vancouver Metro Area,
Columbia River Gorge, and Upper Hood River Valley from 11 AM Sunday
to 10 PM Sunday. Take necessary heat precautions as hot temperatures
may lead to heat illnesses. -Batz/Alviz


.LONG TERM...Monday through Friday...Monday will see a 5-10
degree drop as guidance suggests an upper level shortwave
dropping from the Canadian Rookies into the Intermountain West.
500 mb heights will fall slightly with this disturbance passing
to the east but in general, heights remain above average for
this time of year. Inland highs in the mid to upper 80s are
expected with 60s along the coast.

The Extreme Heat Watch remains in effect Tuesday through
Wednesday; though highs across the region have generally
trended lower based on deterministic model data. The 10th-90th
percentile spread for Tuesday is around 10 degrees across the
inland valleys, generally from low 90s to around 100.
Deterministic forecast highs are around the 25th percentile at
this point, so this large spread in potential is leading to
decreased certainty. Deterministic highs on Wednesday remain in
the mid to upper 90s inland, though the spread between the
10th-90th percentiles is even more pronounced ranging from the
mid 80s to low 100s. The large spread among the guidance is
likely due to the models struggling with the 500 mb pattern and
how pronounced another shortwave trough within the flow
becomes. If the trough strengthens and digs into the PacNW,
expect a "cooler" scenario and if the trough remains weak or
less pronounced expect the higher end of the scenario.

The latest guidance suggests a 20% chance that temperatures reach
100 degrees or hotter across the Willamette Valley on Tuesday, a
decline from the past few days of guidance. Tuesday night low
temperatures have also come down a few degrees as well, but lows
between 65 and 70 degrees are still possible especially around the
Portland/Vancouver Metro Area and Columbia River Gorge. Guidance
suggests a 30-50% chance that Tuesday night lows remain above 65
degrees and a 10% chance low temperatures remain above 70 degrees,
which would limit overnight relief. The current Watch encompasses
areas where overnight low temperatures may struggle to fall below 65
to 70 degrees. As a reminder, an Extreme Heat "Watch" is issued when
dangerous heat is possible. An Extreme Heat "Warning" is issued when
dangerous heat is happening or about to happen.

In addition to the heat, some models are also indicating a thermal
trough developing over the Willamette Valley Tuesday night to
Wednesday. If this occurs, then it would lead to more offshore flow.
Currently, the easterly winds forecast with this thermal trough are
not looking very strong, and will mainly be through the Columbia
River Gorge and Cascades. Current guidance shows pressure gradients
of -2 to -5 mb through the Gorge Tuesday and Wednesday, which would
lead to wind gusts up to 20-25 mph in that area. Minimum relative
humidity are also forecast to fall Tuesday-Wednesday into the 20-30%
range. Will continue to monitor potential fire weather concerns.

Days 6 and 7 in this forecast continue the large uncertainty trend
with potential for a big cool down or another day of hot conditions
on Thursday. Deterministic values are suggesting low to mid 90s
throughout the inland valleys but the 10th-90th percentile
spread is significant, ranging from mid 70s to low 100s.
Ensemble guidance is really struggling with the pattern for the
latter half of next week with a 50/50 split between troughing
or weak ridging across the PacNW. Model spread should decrease
as the lead time becomes shorter. -Batz/Alviz


&&

.AVIATION...High pressure over the area. Current conditions
exhibit some upwelling along the coast once more producing low
stratus and some fog just near the coastline. Conditions are
beginning to clear though giving a break to areas around KONP
which were socked in with low stratus nearly all day yesterday.
Northerly flow over the area will increase through the afternoon
with daytime heating. Gustiest winds will be in areas with a north
to south alignment, especially along the coast and the Willamette
Valley. Along the coast, the northerly winds will promote more
upwelling though and lower stratus may rebuild into area terminals
and thus keep conditions variable. Have maintained more
optimistic forecast, but cannot rule out a return to IFR CIGs.

Overnight expect conditions inland to remain VFR over the next 24
hours.

PDX AND APPROACHES...VFR CIGs and VIS. Gusty winds in the
afternoon with daytime heating. Generally northerly winds aloft up
to 30 kt between 02-10Z Sunday at 2000 ft. For higher approaches
around FL040 northeast gusts up to 35 kt during that time.
-Muessle

&&

.MARINE...Strong high pressure remains over the eastern
Pacific with low pressure over northern CA and eastern OR/WA
increasing in the afternoon and evening hours and decreasing
after sunset. This will cause a diurnal ebb and flow of
tightening pressure gradients over the waters through the
weekend into early next week and therefore increased north
winds. Expect winds to increase from south to north each
afternoon with gusts up to 25-30 kts south of Cape Falcon,
decreasing slightly after sunset. However, small craft advisory
winds of over 21 kts expected to remain for most of the waters
south of Cape Falcon after 11 AM today into early next week.
Therefore, a small craft advisory has been issued. These winds
could also surge north of Cape Falcon Sunday late
afternoon/evening, as well. Seas will build to 7 to 9 feet at 11
seconds by this afternoon, continuing through the weekend. -HEC

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Extreme Heat Watch from Tuesday afternoon through Wednesday
     evening for ORZ108>115-119>122.
     Heat Advisory from 11 AM to 10 PM PDT Sunday for ORZ109-111-
     112-114>118-120>122.
WA...Extreme Heat Watch from Tuesday afternoon through Wednesday
     evening for WAZ204>207-209-210.
     Heat Advisory from 11 AM to 10 PM PDT Sunday for WAZ205>207-
     209-210.
PZ...Dense Fog Advisory until 11 AM PDT this morning for PZZ210-
     251>253.
     Small Craft Advisory until 5 PM PDT Sunday for PZZ252-253-272-
     273.
&&

$$

www.weather.gov/portland

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