053
FXUS66 KPQR 122142
AFDPQR

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

.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 18Z Thu...Westerly flow aloft continues as
an upper level trough moves over the region. Marine stratus
has cleared at most inland terminals. Any lingering stratus
should clear by 22z Wed. MVFR conditions are being observed
along the coast. Lowered flight conditions are expected to
persist through the TAF period along the coast with around a 50%
chance of brief improvement to VFR/high MVFR in the afternoon
hours through 00z Thu. Then there`s a 60-80% chance that
IFR/LIFR conditions return along the coast between 02-06z 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 are expected to increase to around 8-10 kt this afternoon,
decreasing by 04-08z Thu.

KPDX AND APPROACHES...Expect MVFR CIGs to persist through 19-21z
Wed, improving to VFR after. Lingering afternoon clouds are
expected to gradually lift and scatter out, with 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 improve to VFR
conditions again by 18-20z Thu. Northwest winds around 5 kt are
expected to increase to 8-10 kt after 23z Wed, decreasing after
06-08z Thu.      -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.

&&

&&

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

$$

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