046
FXUS66 KPQR 140427
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
927 PM PDT Thu Aug 13 2026

Updated aviation discussion.

&&

.SYNOPSIS...Warm and dry conditions expected through the
weekend with persistent onshore flow. Skies become hazy this
afternoon as some wildfire smoke drifts over the area. Slight
chance (10-20%) for thunderstorms or showers over the Cascades
Friday and Saturday afternoons, with the highest chances along
the crest of the Cascades.

&&

.DISCUSSION...Tonight through Wednesday...Upper level
troughing remains over the region with onshore flow in the
lower levels. One nuance, however, is in the mid-levels of the
atmosphere (5,000-10,000 ft above ground), where forecast
soundings are showing light easterly winds. This is resulting in
some smoke from the Grasshopper, High Lava, Mitchell Fires to
drift into the central and northern Willamette Valley. As the
evening progresses, some of this smoke will likely mix-down to
the surface. However, this smoke is expected to be short-lived
as winds from the west/northwest return tonight into Friday
morning and push smoke eastward and clear the air once again.

By Friday, the upper level trough broadens even further off the U.S.
West Coast. As more southerly flow aloft returns over the area, will
see increasing instability and monsoonal moisture that will support
a 10-20% chance for thunderstorms across the Cascades both Friday
and Saturday afternoons/evenings, with the highest chances
along the crest of the Cascades. Otherwise, the general airmass
remains too dry to support any widespread precipitation from
this trough. Guidance suggests high confidence for near to
slightly above average temperatures for mid-August through the
weekend, with afternoon highs warming into the mid to upper 80s
across interior valleys. By Sunday, there is increasing confidence
of the upper trough offshore becoming more elongated with low
pressure dropping south, well off the California coast. This
could allow for upper ridging over the intermountain west to
shift slightly west, nudging into the Pacific NW. But the main
axis of the ridge is expected to stay eat of the region.

Cluster analysis of 500 mb heights continues to show a wide
range of the magnitudes and placements of an upper level trough
offshore. Still, a slight cooling trend to closer to average
temperatures is possible by the middle of next week with no
precipitation in the forecast.

&&

.AVIATION...Through 06Z Sat...West to southwesterly flow aloft
as an upper level trough remains over the airspace. MVFR/IFR
conditions have developed along the coast in marine stratus. These
conditions will continue through the majority of the TAF period
with a 50-70% chance of LIFR cigs at any given hour through 18z
Fri. There`s a 20-40% chance that stratus could briefly improve
to VFR along the coast at any point through 18z Fri through 02z
Sat, though this improvement would not last long. Northwest to
west winds less than 8 kts continue along the coast through the
TAF period.

Predominately VFR conditions expected for inland terminals through
the TAF period. There`s the potential for marine stratus to push
inland in the early morning hours with a 20-40% chance of MVFR
cigs for most inland terminals except for a 50-70% chance at KEUG
at any hour between 10-18z Fri. Additionally, smoke aloft
continues to impact NW OR and SW WA and could mix down to the
surface at times. Smoke could impact slant range visibilities for
inland locations through Friday afternoon. North to northwest
winds become light and variable overnight through Friday morning,
becoming westerly after 18z Fri.

KPDX AND APPROACHES...Generally VFR conditions through the TAF
period. There`s a 30-50% chance of MVFR cigs developing at any
hour between 12-18z Fri. Smoke in the mid levels could impact
slant range visibilities through Friday afternoon and mix to the
surface at times. Northwest winds less than 6 kts become variable
overnight through Friday afternoon, becoming northwest again after
22z Fri. -03

&&

.MARINE...No significant changes in the overall pattern as high
pressure offshore will continue to support northerly winds
along with fairly benign conditions across all waters into the
weekend. Winds from the north to northwest with gusts less than
21 kts will continue through at least the weekend, with wind
driven seas expected to remain around 3 to 6 ft. /42

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&

$$

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