083
FXUS66 KPQR 121011
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
311 AM PDT Sat Jul 12 2025

.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...Northerly flow aloft remains in place across the
region through the weekend. IFR/LIFR conditions continue along the
coast through around 16-18z Saturday, when stratus is expected to
clear with VFR conditions returning.

There remains the low potential for stratus to develop along the
mouth of the Columbia River and move eastward along the river into
the Portland Metro area. There`s a 40-60% chance MVFR ceilings
associated with the stratus makes it as far south as KKLS after
09z Saturday but only a 20% chance it reaches KPDX after 12z
Saturday. There is not enough confidence to include in TAFs at
this time. Locations that do see stratus should clear by 16-19z
Saturday. Light northerly winds increase in the Willamette Valley
and along the coast after 18z Saturday. Expect occasional gusts up
to 20-25 kts inland and up to 25-30 kts along the coast through
around 03-06z Sunday.

PDX AND APPROACHES...VFR conditions are expected to persist
throughout the period. A low probability (20%) of MVFR CIGs
developing overnight remains between 10-16z Saturday, but any
such conditions would likely be brief and dissipate quickly after
sunrise. While elevated winds are present between 1000-2500 ft
around 12Z Saturday, the lack of significant directional shear
means LLWS is not a concern. North winds less than 10 kts increase
after 21z Saturday with occasional gusts up to 20 kts possible
00-06z Sunday. -HEC

&&

.MARINE...Upwelling along the coast is keeping marine stratus in
place with marine fog expected through this morning. A Dense Fog
Advisory remains in effect for the inner waters with visibility
of 1 NM or less expected through the morning.

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 PZZ251>253.

     Small Craft Advisory from 11 AM this morning to 5 PM PDT Sunday
     for PZZ252-253-272-273.
&&

$$

www.weather.gov/portland

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