540
FXUS66 KPQR 141726 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1026 AM PDT Fri Aug 14 2026

Updated Aviation Discussion

.SYNOPSIS...Warm and dry conditions expected through next week
with persistent onshore flow. Slight chances (10-20%) for
thunderstorms or showers over the Cascades this afternoon and
Saturday afternoon, with the highest chances along the crest of
the Cascades.

&&

.DISCUSSION...Today through Thursday...Satellite imagery and
surface observations as of early Friday morning depicts onshore
flow supporting a solid marine layer along the coast with
stratus clouds pushing through the gaps of the Coast Range and
through the Lower Columbia River into the Cowlitz Valley. By 5-7
AM Friday, expect stratus clouds to make it`s way into the rest
of the I-5 corridor including the Willamette Valley. After 9-11
AM Friday, clouds across interior valleys should begin clearing
out as daytime heating progresses and increases mixing.
Meanwhile, there remains uncertainty with how much clearing will
occur at the coast. There is about a 50-60% chance at any given
hour between 2-7 PM for marine stratus breaking out along the
north Oregon coast, but lower confidence for clearing along the
central Oregon coast.

Expect dry and warm conditions today and through the weekend for
the majority of locations as weak ridging builds over the
Pacific Northwest and an upper level trough elongates well-
offshore over the northeast Pacific Ocean. An exception would be
the Cascades, where there is a 10-25% chance for isolated
thunderstorms this afternoon and Saturday afternoon. As
shortwaves from the broad parent trough offshore brings more
southerly flow aloft over the area, will see increasing
instability and monsoonal moisture supporting these thunderstorm
chances. Any thunderstorms that develop may bring lightning,
brief heavy rain, and erratic winds. Otherwise, the general
airmass remains too dry to support any widespread precipitation
west of the Cascades. 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.

Early next week, cluster analysis of 500 mb heights continue to
suggest dry and seasonably warm conditions as broad upper level
troughing remains well-offshore and an upper level ridge axis
over the Rockies tilts into the Pacific Northwest. By mid-week,
ensembles diverge into various upper level patterns. A little
over half of ensemble members are favoring a trough entering the
Pacific Northwest and returning cooler temperatures, while the
other half favors warmer conditions due to zonal flow or
amplified ridging. Either way, no precipitation is forecast as
we maintain a dry summertime airmass.     -10

&&

.AVIATION...Through 18Z Sat...Morning satellite imagery and
terminal observations show a mixture of widespread marine stratus
and smoke/haze across the airspace. This is resulting in MVFR
conditions for inland locations and MVFR to LIFR conditions along
the coast.

Guidance is suggesting that the MVFR conditions within the
Willamette Valley will improve to VFR around 18Z-20Z Friday, while
coastal locations are expected to maintain MVFR conditions
through at least 06Z Saturday. Afterwards, conditions along the
coast are expected to fall back towards IFR/LIFR for the remainder
of the TAF period. As for inland locations, MVFR conditions via
marine stratus are expected to return around 10Z-12Z Saturday and
will persist through the remainder of the TAF period. Westerly to
northwesterly winds generally around 5-10 kt today, strongest in
the afternoon.

From 20Z Friday through 06Z Saturday, smoke will likely mix down
at times and could impact visibilities. Smoke/haze across the
airspace could impact slant range and vertical visibilities
anytime through 06Z Saturday for inland locations.

Starting around 10Z Saturday and through at least the end of the
TAF period, models are showing around a 10% chance for elevated
thunderstorms developing anywhere within the Willamette Valley.
Any thunderstorms that develop could result in frequent lightning,
small hail as well as gusty and erratic winds.

KPDX AND APPROACHES...MVFR conditions through around 20Z Friday,
scattering out and improving to VFR afterwards. MVFR conditions
expected to return around 12Z-15Z Saturday. Northwesterly winds
around 3-7 kt, strongest in the afternoon. From 20Z Friday
through 06Z Saturday, smoke will likely mix down at times and
could impact visibilities. Smoke/haze across the airspace could
impact slant range and vertical visibilities anytime through 06Z
Saturday. /42

&&

.MARINE...No significant changes in the overall pattern as high
pressure offshore will continue to support northerly winds along
with benign conditions across all waters through next week. 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 3-5 ft. -10/42

&&

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

&&

$$

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