102
FXUS66 KPQR 130953
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
253 AM PDT Thu Aug 13 2026

.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
(10-15%) for thunderstorms or showers over the Cascades Friday and
Saturday afternoons, 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 Wednesday...Nighttime RGB satellite
shows marine stratus solidly entrenched along the coast, while
broken to scattered clouds are developing around the Portland Metro
area. Any morning clouds will scatter out across inland lowlands by
afternoon providing another day of mostly sunny skies and
temperatures warming into the mid-80s. Upper level troughing remains
over the region today 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 returning, including near the Grasshopper Fire. This
could cause some wildfire smoke to drift across portions of
northwest Oregon and southwest Washington by this 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.

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 each
afternoon, both Friday and 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 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.

The possibility for widespread rain early next week has dropped
significantly, as chances for measurable precipitation (>0.01") are
very low (15% or less) across the area Monday through Wednesday.
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. DH/10

&&

.AVIATION...Through 12Z Fri...Westerly flow aloft becomes
southwesterly later this morning 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 40-50% chance that IFR/LIFR conditions
return along the coast between 10-18z Thu. Chances of marine
stratus pushing inland during this time is lower with a 30-50%
chance of MVFR ceilings at any hour between 10-16z Thu at inland
terminals. Any lowered ceilings that do form should improve by
18-20z Thu. North to northwest winds increase to 8-10 kts after
21z Thu.

KPDX AND APPROACHES...Predominately VFR conditions likely through
the TAF period. However, there is a 30-40% chance of MVFR CIGS
developing again between 10-16z Thu. If these formed, expect
improvement to VFR conditions by 17-19z Thu. Northwest winds
around 5 kt are expected to increase to 8-10 kt after 23z Thu. /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/03

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

www.weather.gov/portland

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