499
FXUS66 KPQR 221102
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
402 AM PDT Wed Jul 22 2026

.SYNOPSIS...
Hot and increasingly humid conditions will continue
today, with another round of very warm overnight temperatures
limiting recovery across the interior. Highs this afternoon will
again reach the 90s for most inland locations, and a few spots
may touch 100 degrees before cloud cover and convection begin to
temper heating. Monsoonal moisture spreading northward will
bring a rising chance of showers and thunderstorms today,
especially from afternoon into evening, with the greatest risk
over the Cascades. Cooler weather is then expected Thursday and
beyond as onshore flow strengthens.

&&

.SHORT TERM...Now through Thursday...There are two concerns
today: heat and increasing convective potential. Upper ridging
remains in place today, and warm overnight temperatures have
once again left much of the interior with poor overnight cooling
heading into the new day. That sets the stage for another hot
afternoon, although the temperature forecast is more complicated
due to increasing mid and high level moisture advancing
northward.

For the heat portion of the forecast, inland locations remain
on track to climb well into the 90s again today, with the
warmest interior valleys having at least some chance to reach
the upper 90s to near 100 degrees (notably around the
Portland/Vancouver metro). The exact high temperature today
will depend in part on how quickly cloud cover increases and how
much sunshine can be maintained into the afternoon. Even if
highs end up a few degrees lower than peak potential, the added
humidity will make conditions feel more oppressive than on
previous days. A Heat Advisory remains in effect through this
evening for much of the interior lowlands, including the
Portland/Vancouver Metro, the Columbia River Gorge including
Hood River County, Kelso/Longview, and portions of the south
Washington Cascades. Major HeatRisk remains a concern for much
of the Willamette Valley, especially where overnight
temperatures stay elevated and afternoon heat builds before
storms develop.

The more active part of the forecast arrives later today as
monsoonal moisture and an offshore low work together to
destabilize the atmosphere. Guidance continues to suggest that
at least isolated convection could begin as early as 11 AM this
morning in a few locations, but confidence is notably greater in
development from 1 PM this afternoon to 7 PM this evening when
daytime heating can maximize instability. The favored area for
thunderstorm development continues to be the Lane and Linn
County Cascades and nearby Willamette National Forest, though a
few storms could develop farther west as well if sufficient
breaks in cloud cover allow instability to build. This is
reflected in the latest SPC convective outlook, which depicts a
general thunderstorm risk across much of southwest Washington
and northwest Oregon, with a marginal risk focused over the
Oregon Cascades. It is critical that if you hear thunder or see
lightning that you take cover immediately inside of a sturdy
structure, get off of the water, and limit outdoor activities.

Forecast soundings and convective guidance continue to support
an environment capable of thunderstorms, with elevated
instability in place and precipitable water (PWAT) values
around 1.2 to 1.5 inches. While that amount of moisture could
support pockets of locally heavier rainfall, relatively dry air
in the lower levels may reduce rainfall efficiency in some
locations. While lightning remains the primary concern, locally
gusty and erratic winds may accompany any stronger storms,
especially near the Cascades. A more scattered thunderstorm
scenario cannot be ruled out this afternoon and evening,
particularly over the higher terrain.

Showers and thunderstorms may linger into tonight, though
coverage and intensity should gradually diminish after sunset as
surface-based instability weakens. A few showers could persist
into Thursday morning before the broader pattern begins to
shift.

.LONG TERM...Thursday Night through Tuesday...By late Thursday
into Friday, upper ridging will weaken while a broader trough
moves toward the Pacific Northwest. This will allow onshore flow
to re-establish itself and bring a more noticeable cooling
trend late this week, along with a return to more marine
influence and night/morning cloud cover. Confidence is moderate
to high in the overall cooling trend, though lower in the exact
day-to-day temperatures. Temperatures should remain somewhat
above seasonal averages Thursday and Friday, but well below the
temperatures reached earlier in the week, with improved
overnight recovery as well. Looking into the weekend and early
next week, temperatures appear likely to settle back into the
upper 70s to lower 80s inland, with no strong signal for
meaningful precipitation after Friday, though light shower
chances may linger Saturday along the north Oregon coast and
south Washington coast.
~12

&&

.AVIATION...Through 12Z Thursday...VFR conditions with sct/bkn
high clouds inland will continue through most of the TAF period,
with the exception of marine stratus potentially pushing inland
late Wednesday, bringing a 20-30% chance of MVFR conditions
after 06Z Thu. Periods of haze from elevated smoke may restrict
vis to 5-6 SM in the afternoon at inland terminals. As for
coastal terminals, current LIFR conditions will likely improve
back to VFR conditions by 16-18Z Wed. Marine stratus will then
likely creep back in from south to north, returning KONP to
LIFR/IFR conditions around 00Z Thu, then to KTMK around 06Z Thu,
and to KAST by 09Z Thu. There is less confidence for these
conditions at KAST compared to KONP, with a 30-40% chance of IFR
at KAST but a 80-90% chance at KONP. Additionally, there is a
20-40% chance of LIFR at KAST but 50-70% chance at KONP.

Otherwise, winds will be calm to light and variable early this
morning, building out of the west to northwest at 5-10 kt
inland and 9-14 kt along the coast after 18-21Z Wed. KEUG and
KSLE are an exception, with winds around 9-14 kt expected.
Coastal terminals and KEUG/KSLE may see gusts up to 20 kt during
the afternoon. Winds will begin to shift more west to
southwesterly after 03Z Thu.

Afternoon temperatures are forecast to approach 100 degrees at
many inland terminals this afternoon; be aware of high density
altitude which may reduce aircraft performance. Showers and
isolated thunderstorms are expected to develop this afternoon,
tracking northward through the remainder of the period.
Confidence in the occurrence of thunder is too low to include in
TAFs at this time, but heavy showers may briefly result in
MVFR/IFR vis if they pass over a terminal. Showers may also
produce gusty or erratic winds nearby. Late in the period, winds
will begin to turn out of the southwest to south as showers
wane.

KPDX AND APPROACHES...VFR conditions and sct/bkn high clouds
through most of the TAF period. There is a 20-30% chance of MVFR
CIGs after 06Z Thu. Smoke aloft may yield surface vis of 5-6 SM
this afternoon, although vis aloft can often be lower. Chances
for showers or an isolated thunderstorm increase after 00z Thu;
the most likely terminal impacts are gusty/erratic winds and
locally heavy downpours which may briefly restrict vis to
IFR/MVFR levels. Northwest winds continue through the period at
5 kt or less overnight, building to 5-10 kt by this afternoon.
Winds will shift more west to southwesterly after 03Z Thu.
~12/36

&&

.MARINE...
North to northwest winds over the coastal waters will shift to
west to southwesterly late today and through 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.

Today, there is a chance for showers and thunderstorms across
all of the waters through the majority of the day and overnight
hours. There could be frequent lightning and gusty and erratic
winds with any thunderstorm that forms.
~12/03

&&

.CLIMATE...
Daily record high minimum temperatures for July 22
Astoria 62 (2007)
Vancouver, WA 74 (2006)
Portland Int`l 74 (2006)
Hillsboro 73 (2006)
McMinnville 73 (2006)
Salem 74 (2006)
Eugene  71 (2006)

Daily record high maximum temperatures for July 22
Astoria 88 (1891)
Vancouver, WA 98 (1928)
Portland Int`l 98 (1978, 2004)
Hillsboro103 (1938)
McMinnville102 (1928)
Salem102 (1928, 1978)
Eugene101 (2006)

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory until 11 PM PDT this evening for ORZ108>115-
     120>122.
WA...Heat Advisory until 11 PM PDT this evening for WAZ204>210.
PZ...None.
&&

$$

www.weather.gov/portland

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