576
FXUS66 KPQR 120944
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
244 AM PDT Wed Aug 12 2026

.SYNOPSIS...Warm and dry conditions expected through the weekend
with persistent onshore flow. A stronger onshore push will bring
increasing clouds and cooler temperatures today. Mostly dry through
the weekend, with a chance of thunderstorms or showers over the
Cascade crest Saturday afternoon. There are low chances for more
widespread rain returning early next week, but significant rain does
not appear likely.

&&

.DISCUSSION...Today through Tuesday...Water vapor satellite imagery
shows an upper level trough dropping out of British Columbia into
the Pacific NW. This trough will allow for marine stratus to spread
inland across much of SW Washington and NW Oregon with clouds
lingering into the morning and early afternoon. Slightly cooler
conditions are expected today with highs ranging from the mid-70s to
lower 80s, while the coast likely remains in the 60s. Would not be
surprised for some drizzle at the coast this morning as the marine
layer deepens. Most of the moisture associated with the
aforementioned trough is expected to remain across portions of the
northern half of Washington, keeping us dry.

There is agreement among the models and their ensembles for
later in the week with the upper level pattern trending toward broad
upper level troughing and a continuation of onshore flow. One nuance
in the mid-levels on Thursday will be some light easterly winds in
the 850-700 mb levels of the atmosphere, including near the
Grasshopper Fire. This could cause some wildfire smoke to drift
across portions of the area, mainly causing hazy skies by Thu
afternoon. The potential range of afternoon high temperatures from
the NBM for Thursday through Friday has generally consolidated into
the lower to mid-80s, favoring near to slightly above average
conditions for mid-August.

Some uncertainty into the weekend, but ensembles are suggesting weak
upper level ridging may nudge back into the Pacific NW as low
pressure deepens the upper trough offshore. The latest cluster
analysis shows more consistency between the models of low pressure
dropping south off the central CA coast. This could result in a
slight warming trend, though models suggest there is only a 10-20%
chance of exceeding 90 degrees across the Willamette Valley on
Sunday and Monday. Shortwave troughs within the more southwesterly
flow aloft along with some increasing monsoonal moisture will also
bring slight chances (10-20%) for thunderstorms along the Cascade
crests of Oregon for Saturday afternoon, with the highest chances
across the Lane County Cascades.

The question then turns to the possibility of rain early next
week, but chances for measurable precipitation remains low (15-30%)
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 10-15% of ensembles show the
potential for any substantial rainfall (24 hour totals of > 0.25")
across the area. DH/10

&&

.AVIATION...Westerly flow aloft continues as an upper level trough
moves over the region. Marine stratus with IFR to LIFR conditions
is entrenched along the coast and expected to persist through much
of the TAF period. Improvement to MVFR (or better) CIGs is most
likely at KAST by 21z Wed, while KONP holds onto a 50% chance for
IFR to persist through this afternoon.

A stronger marine push is expected to continue to spread stratus
inland this morning, with MVFR CIGs most likely, starting at
around 10-14z Wed. MVFR conditions are expected to persist until
around 18-20z Wed. Then, predominately VFR expected with skies
gradually clearing. North to northwest winds are expected to
increase to around 10 kt this afternoon.

KPDX AND APPROACHES...Low stratus is beginning to develop around
the Portland Metro area. Expect MVFR CIGs to persist through
18-19z. Afternoon clouds are expected to gradually lift and
scatter out, with predominately VFR conditions likely through the
evening. Northwest winds around 4-8 kt are expected, strongest in
the afternoon and evening. /DH

&&

.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

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

www.weather.gov/portland

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