215
FXUS66 KPQR 130446
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
946 PM PDT Wed Aug 12 2026

Updated aviation discussion.

&&

.SYNOPSIS...Warm and dry conditions expected through the
weekend with persistent onshore flow. Slight chance (10-15%) for
thunderstorms or showers over the Cascades Friday to Saturday
afternoon, with the highest chances along the crest. There are
low chances for more widespread rain returning early next week,
but significant rain does not appear likely at this time.

&&

.DISCUSSION...Today through Tuesday...Satellite imagery and
surface observations as of early Wednesday afternoon depicts
stratus clouds dissipating across interior valleys. So far, the
central and southern Willamette Valley have cleared out, and we
are beginning to see the northern Valley and southwest
Washington lowlands clearing out as daytime heating progresses.
We`re also seeing some cumulus clouds popping up across the
Cascades and Coast Range due to increasing instability and
moisture from an upper level trough; however, expect to remain
dry today. The better moisture for precipitation is further
north across the northern half of Washington. Given the
widespread cloud cover this morning, temperatures are forecast
to peak in the upper 70s across interior valleys and 60s along
the coast.

Tomorrow (Thursday), models and their ensembles continue to
agree on upper level troughing broadening over the Pacific
Northwest and maintaining onshore flow as a ridge over the
northeast Pacific flattens out and weakens. One nuance is in the
mid-levels of the atmosphere (5,000-10,000 ft above ground)
tomorrow, where forecast soundings are showing light easterly winds
returning, including near the Grasshopper Fire. This could
cause some wildfire smoke to drift across portions of northwest
Oregon and southwest Washington by Thursday afternoon, mainly
causing hazy skies. Can`t rule out some of this smoke mixing
down to the surface as well. However, this smoke is expected to
be short-lived as winds from the west return Thursday night into
Friday morning and push smoke eastward and clear the air once
again. Still not expecting precipitation, but some lingering
moisture to the north could support a 10-15% chance for
thunderstorms across the far northern portions of the south
Washington Cascades Thursday afternoon.

By Friday through the weekend the aforementioned 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 10-15%
chance for thunderstorms across the Cascades each afternoon from
Friday-Saturday, 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 tomorrow through the weekend, with
afternoon highs rebounding into the mid to upper 80s across
interior valleys.

The question remains whether or not we get widespread rain early
next week, but chances for measurable precipitation (>0.01")
remains low (15-25%) across the area next Monday and Tuesday.
Cluster analysis of 500 mb heights shows a wide range of the
magnitudes and placements of the upper level trough offshore,
while only 5-10% of ensembles show the potential for any
substantial 24-hour rainfall totals above 0.10" across the area.
                                                 -10/DH


&&

.AVIATION...Through 06Z Fri...Westerly flow aloft continues as an
upper level trough remains over the region. Marine stratus with
MVFR cigs has returned to the coast. Expecting at least MVFR cigs
along the coast for nearly the entire TAF period with a 50% chance
of conditions clearing to VFR for a few hours at any point between
18z Thu to 00z Fri. Additionally, there`s a 60-80% chance that
IFR/LIFR conditions return along the coast between 06-10z Thu.
The marine push will be less strong tonight into Thursday morning,
so chances of marine stratus pushing inland during this time is
lower with a 25-40% chance of MVFR ceilings at any hour between
10-16z Thu at inland terminals. Any lowered ceilings that do form
should improve by 18-21z Thu. North to northwest winds decrease
to around 5 kts or lower by 08z Thu. Winds increase to 8-10 kts
again after 21z Thu to 00z Fri.

KPDX AND APPROACHES...Predominately VFR conditions likely through
the rest of the TAF period. However, there is a 25-40% chance of
MVFR CIGS developing again between 10-14z Thu. If these formed,
expect improvement to VFR conditions by 17-20z Thu. Northwest
winds around 5 kt or less are expected to increase to 8-10 kt
after 23z Thu, decreasing after 06-08z Fri. -03

&&

.MARINE...No significant changes as high pressure offshore will
continue to support northerly winds and fairly benign
conditions across the coastal waters through the week and into
the weekend. Winds from the north to northwest with gusts less
than 21 kts will continue through at least the end of the week.
Wind driven seas are expected to remain around 3 to 6 ft through
the week.
                                                  -DH/03

&&

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

&&

$$

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