366
FXUS66 KPQR 210500
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1000 PM PDT Mon Jul 20 2026

Updated aviation discussion.

&&

.SYNOPSIS...Ever-changing pattern this week with a warming
trend on Tuesday into Wednesday. Higher confidence on Tuesday`s
highs being well above normal, but some level of uncertainty
lies with Wednesday still as there is another potential weather
pattern that would disrupt as significant of heating.
Thunderstorms remain possible on Wednesday, especially over the
Lane and Linn county Cascades. Cooler with onshore flow starting
Thursday.

&&

.SHORT TERM...Now through Wednesday Night...Satellite imagery
this afternoon shows widespread cloud cover over the region
which has maintained more moderate temperatures throughout the
area. Starting to see temperatures rise, but it has been a slow
process. Still expecting highs in the mid to upper 80s inland,
with cooler temperatures along the Coast, southwest Washington
and the Cascades.

Tuesday continues to be on track for a significantly warmer day
as high pressure builds over the region. This ridge is going to
maintain generally clear skies with light winds overnight. Night
time temperatures will remain elevated, especially with the aid
of cloud cover that fills in overnight. The HREF continues to
show a return of southerly flow and cloud cover on Tuesday
which, if combined with smoke aloft, could inhibit significant
heating. This trend can be observed when comparing models. For
example, the NBM is showing around 98 degrees for a high on
Tuesday, while the HREF is closer to 95 degrees in Portland.
While not a significant drop, it does show that there remains
some wiggle room. This is further supported when looking at the
probabilities. In Salem for example (also in the Heat
Advisory), the temperatures in the 25th to 75th percentile range
from 96-100 degrees F. There is a 10% chance that highs could
reach around 101 degrees on Tuesday. The Heat Advisory remains
in effect through Wednesday.

Speaking of Wednesday, that is where conditions become a little
be less confident. Ensembles continue to agree on a ridging
pattern persisting, but where it ends up is the question.
Northwest Oregon and Southwest Washington is sitting right on
the outer edge of the ridge which is going to increase southerly
to southwesterly flow. In addition, there is moisture in the
area from a trough aloft forming off of the coast of California.
This trough would disrupt the potential for another significant
heating day, and instead bring higher cloud cover and even the
potential for rain/thunderstorms. Right now, the trend remains
warm, but more and more of the models are showing increasing
convection risk. CAPE values over the Cascades are increasing,
and looking at forecast soundings, a lot of that instability is
aloft. If we maintain lots of cloud cover, the initiation for
storms will be limited as the flow aloft is less strong than the
last thunderstorm outbreak we experienced. However, if we get
the cloud breaks, we could easily see these storms perk up and
we could see some elevated thunderstorms. PWATs remain around 1
inch which is a tad lower and would lead towards a dry
thunderstorm scenario.

Multiple days of above normal heat combined with limited
overnight relief will support widespread Moderate HeatRisk
across much of the interior. The greatest concern remains
centered on the Portland/Vancouver metro, the Columbia River
Gorge including Hood River County, and the Kelso/Longview area,
where a Heat Advisory is in effect from Tuesday morning through
at least Wednesday evening. Within those areas, Major HeatRisk
appears increasingly likely Tuesday and Wednesday, especially in
locations that see the warmest afternoons and the least
nighttime cooling. Those with outdoor plans or without effective
cooling should be prepared for elevated heat impacts. So, drink
plenty of fluids, stay in a cool place during the heat of the
day, stay out of the sunshine, and check up on relatives and
neighbors. -27


.LONG TERM...Thursday through Monday...By Thursday and Friday,
the ridge is expected to weaken as a broader trough begins to
press into the Pacific Northwest. That should allow temperatures
to ease a few degrees late in the week, though values may still
remain somewhat above average for late July. Beyond Friday,
there is currently no strong signal for meaningful
precipitation, and temperatures remain mild in the mid 80s. -12

&&

.AVIATION...Continued VFR flying conditions expected throughout
the period at inland terminals with sct/bkn high clouds and
unrestricted vis. Nearly calm winds tonight will build to around
5 kt out of the north to northwest by 16-20z Tue.

Along the coast, resurgent low marine stratus is again expected,
favoring IFR/LIFR conditions through much of the overnight
period. LIFR cigs/vis are favored (80% chance of occurrence)
at KONP, with chances decreasing to the north; IFR conditions
are instead favored (60% chance) at KAST. Slow improvement to
MVFR/VFR is expected after 16-18z Tue. Nearly calm winds tonight
will build out of the west to northwest at 5-10 kt by 18-21z Tue.

KPDX AND APPROACHES...VFR conditions beneath sct/bkn high clouds
and light northwest winds are expected. Winds will build
slightly to 4-8 kt by Tuesday afternoon. -36

&&

.MARINE...A typical summertime pattern will continue through
the middle of this week with persistent north to northwest winds
over the coastal waters. Winds then shift southwest to westerly
Thursday into the weekend as weak low pressure develops over
the waters. Winds will remain light less than 10-15 kts. Seas
will be 3-6 ft at 8-9 seconds through the weekend. -03

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Heat Advisory from 10 AM Tuesday to 11 PM PDT Wednesday for
     ORZ108>115-120>122.

WA...Heat Advisory from 10 AM Tuesday to 11 PM PDT Wednesday for
     WAZ204>207-209-210.

PZ...None.

&&

$$

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