487
FXUS66 KPQR 211116
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
416 AM PDT Fri Aug 21 2026

.SYNOPSIS...Low pressure brings chances for showers Friday
evening into Saturday across northwest Oregon and southwest
Washington, with a 15-20% chance for thunderstorms over the
Cascades and 5-10% chance elsewhere. Winds out of the
west/southwest on Saturday. Seasonable weather returns Sunday
through the middle of next week.

&&

.DISCUSSION...Today through Thursday...An upper level trough
over the northeast Pacific will shift toward the PacNW today,
supporting upper level cloud cover, a decrease in temps and a
low chance for precipitation. Highs in the 80s are expected for
interior lowland locations with the warmest temps in the upper
80s in the western Columbia River Gorge and Cascade foothill
valleys. Along the coast, highs top out in the low to mid 60s.

Hi-res models seem to be struggling with the development and
progression of precipitation across the area as the low shifts
over the area. Most likely timing is this evening and into the
overnight hours. As winds shift more southwesterly, PWAT values
are expected to increase to between 1.0-1.30 inches across NW OR
and SW WA. The biggest question will be CAPE over the region.
SBCAPE on the order or 400-800 j/kg is possible over the
Cascades but a strong capping inversion of 50-100 j/kg of CIN
could stifle any development. MUCAPE values are a bit higher in
the 700-1100 j/kg range over the Cascades which indicates some
elevated instability in the mid levels of the atmosphere.
Without a clear forcing mechanism, will maintain the slight
chance PoPs and thunder (both 10-25%) over the area with the
Cascades remaining most likely for any precipitation initially
then shifting north of the OR/WA border as a weak cold front
moves onshore late tonight into Saturday morning. Any showers or
storms will be isolated with most locations likely remaining
dry.

The upper level trough will continue to progress northeast through
the weekend. The weak cold front moving through the area early
Saturday will support temperatures cooler further into the
upper 70s inland while also shifting winds more out of the
west/southwest. Winds through west-east aligned mountain gaps
could be gusty, especially through the western Columbia River
Gorge. Gusts around 30 mph are expected with a 30-50% chance for
isolated gusts around 35 mph Saturday afternoon.

Zonal flow aloft develops Sunday as the upper level trough continues
to trek northeast away from the region. Seasonable highs in the
upper 70s to low 80s are expected across the interior lowlands.
Looking ahead into early next week, ensemble clusters favor ridging
over the central CONUS and influencing the PacNW. Model spread for
high temperatures on Monday increases with the 10th-90th
percentiles ranging from the mid 70s to upper 80s for the
interior lowlands. Confidence increases Tuesday and Wednesday
with highs likely in the mid 80s. Clusters indicate another
trough influencing the region by the middle of the week but
exact timing and upper level pattern are uncertain but onshore
flow and more seasonable temperatures would be favored. -19

&&

.AVIATION...Through 12z Saturday...Marine stratus remains
entrenched along the coast, yielding high confidence in continued
LIFR cigs through at least midday. Brief improvement to IFR
conditions is possible during the late afternoon but chances
remain low. VFR conditions are expected inland for all terminals
with only a low chance for stratus to reach KEUG through the Coast
Range Gaps. Chances for MVFR/IFR CIGs are 15-25% through 17z. Otherwise,
increasing coverage of mid to high clouds at or above 15-25 kft
is expected through much of the period. Light winds overnight,
becoming south/southwest 5-10 kt after 16-18z.

KPDX AND APPROACHES...VFR conditions very likely (85% chance) to
prevail throughout the period beneath increasing mid to high
clouds at or above 15-25 kft. Light and variable winds becoming
southwest around 5 kt late in the morning. -19

&&

.MARINE...Winds shift to the southwest today as a low pressure
system moves over the northeast Pacific. A cold front moves
through Saturday,bringing a 40-70% chance for maximum wind gusts
to exceed 21 kt for the waters north of Cape Foulweather,
including the Columbia River Bar. For the rest of the waters,
chances are 15-30%.

High pressure and northerly winds return by Sunday, with a 30-50%
chance for northerly wind gusts to exceed 21 kts in the late
afternoon and evening hours, with the highest chances south of
Cape Falcon. Seas of 4-6 ft persist through the period. -19/12

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...None.

&&


$$

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