760
FXUS66 KPQR 172145
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
245 PM PDT Thu Jul 17 2025

.SYNOPSIS...Increasing onshore flow will see temperatures
continue to trend cooler toward below-normal values by the
beginning of next week. An upper-level trough may provide the
best rainfall chances in a month on Monday, although odds
remain low for accumulating precipitation. Forecast confidence
then decreases rapidly through the workweek.

&&

.SHORT TERM...Now through Sunday...An initial upper shortwave
continues to weaken as it pushes eastward toward the Northern
Rockies this afternoon. Westerly to northwesterly onshore flow
which developed overnight and into this morning in tandem with
the shortwave passage has cooled temperatures compared to the
peak of the heat yesterday, yielding afternoon highs some 10
degrees cooler throughout inland valleys, and about 5 degrees
cooler along the coast. Similar conditions to today are expected
to end the workweek, namely 60s with morning low clouds and fog
along the coast and mid and upper 80s to around 90F inland.

Another more energetic shortwave will approach the region late
Friday, ushering in further onshore flow and additional cooling.
Slightly cloudier and breezier conditions may develop as soon
as Friday afternoon, most evidently through the Columbia Gorge
where gusts may reach 25-30 mph. Mid-level temperatures will
fall from around 15C on Friday to 10-11C on Saturday, pushing
surface temperatures to below-normal values. Afternoon highs
through the weekend are expected in the low 60s along the coast
and mid 70s to low 80s within inland valleys. Increased marine
stratus coverage may see areas of patchy coastal fog and mist,
most likely overnight and into the morning both days this
weekend, although chances for just 0.01" of accumulating
rainfall remain only 15-25% south of Tillamook, and 25-40% from
Tillamook north to Pacific County, Washington. -Picard


.LONG TERM...Sunday Night through Thursday...The forecast
through the long term period remains lower confidence as
numerical guidance diverges beyond Monday. Troughing initially
present over the Pacific Northwest looks to become more
elongated as a shortwave dives south on its western flank. While
this wave may support light rain reaching into the region Sunday
night into Monday, chances remain low, only 10-20% along the
coast and in the higher terrain of the Cascades and Coast Range
while the lowlands see less than a 10% chance. Ensemble members
then show a wide variety of possible scenarios including a
cutoff low developing over the Pacific or a deamplification of
the trough with an associated warming trend as cooler air in
the mid-levels moderates. At this point, the majority of members
favor the trend back toward a more zonal pattern and the
forecast therefore warms back above seasonal norms. -Picard

&&

.AVIATION...Marine stratus backing off from most of the coast,
though some persistent MVFR stratus remains at the southern coast
(KONP). Satellite imagery shows that there will likely be at
least a few hours of clearing, with VFR likely during that
period. All coastal terminals drop back down to IFR/LIFR with
80-95% confidence around 06z Fri.

Inland, clear sky VFR conditions throughout the period are
expected. Generally west-northwest winds throughout the period,
with sustained winds around 5-8 kts throughout the period.

PDX AND APPROACHES...VFR conditions throughout the period, with
more or less clear skies. West northwest winds around 5-8 kts
throughout the period. /JLiu

&&

.MARINE...A weak surface trough is producing light southerly
winds across the waters today, but winds quickly switch back to
north-northwesterly by evening-time Thursday as high pressure
rebuilds. The incoming northwesterly swell has been
overperforming model output, and seas are currently around 9-10
ft at 10 seconds. A Small Craft Advisory has been issued through
11 AM Friday due to choppy seas. A marine Dense Fog Advisory
has also been pre-emptively issued for marine fog tonight,
beginning 10 PM Thursday and continuing through 2 PM Friday.
Winds weaken and seas subside further heading into the weekend
with minimal impacts expected. /JLiu

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 11 AM PDT Friday for PZZ210-251>253-
     271>273.

     Dense Fog Advisory from 10 PM this evening to 2 PM PDT Friday
     for PZZ251>253-271>273.

&&

$$

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