936
FXUS66 KPQR 190414
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
914 PM PDT Fri Jul 18 2025

Updated aviation discussion.

.SYNOPSIS...Strengthening onshore flow will bring continued
cooling through the weekend with temperatures falling before
normal to begin the next workweek. An upper low passing overhead
Sunday night into Monday may bring the best chances for rain so
far this month, although odds for accumulating precipitation
remain fairly low. Forecast confidence decreases midweek,
although a return to warmer temperatures is most likely.

&&

.SHORT TERM...Now through Sunday...Another upper-level
shortwave passing over or just north of the region this
afternoon and evening will usher in intensified onshore flow,
continuing the cooling trend through the weekend. Mid-level
temperatures around 15C at 850 hPa today will fall to 10-11C by
Sunday afternoon, pushing surface temperatures below seasonal
normals, with afternoon highs falling to the 60s along the coast
and in terrain, and mid 70s to low 80s along the I-5/I-84
corridors. The stronger onshore push will also favor increased
low cloud cover, especially along the coast and into Coast Range
gaps, including up the Columbia River into the
Portland/Vancouver metro. Coastal mist and fog are also most
likely Sunday morning reaching into west-facing Coast Range
valleys. West to northwest winds will also strengthen modestly,
with gusts as high as 30-35 mph through the Columbia Gorge each
afternoon. -Picard


.LONG TERM...Sunday Night through Friday...By Sunday night into
Monday, there is increasing consensus that a vigorous upper
shortwave will dive southward over the Haida Gwaii and
Vancouver Island, resulting in elongated upper troughing or even
a cutoff low centered developing over the Pacific NW. While
this wave may support light rain reaching into the region to
start the workweek, chances remain fairly low, only 15-25% along
the coast and in the Coast Range, and slightly lower in the
Cascades and foothills. It`s worth noting that an increased
number of global ensemble members are showing accumulating rain
as well as anomalously high values of precipitable water,
generally 1-1.25" across the forecast area, which would be above
the 90th climatological percentile of KSLE sounding observations.
With light mean cloud-level winds, around 5 kt, slow-moving
convective showers which could wring out a true wetting rain in
some areas cannot be ruled out.

Numerical guidance then diverges toward the middle of the week
as the evolution of the trough or cutoff low remains somewhat
low confidence. Many ensemble members are continuing to favor
another cutoff upper low developing near Cape Mendocino while
the mean flow to the north returns to a more zonal pattern. In
this scenario, heights rising aloft and moderating mid-level
temperatures would favor a warming trend at the surface, while
southerly to southeasterly flow about the eastern flank of the
upper low could generate convection over the Cascades. -Picard

&&

.AVIATION...MVFR/IFR stratus has filled in along the coast while
inland terminals remain VFR. A stronger marine push may result in
sct-bkn low stratus reaching up the Columbia River to Portland-
area terminals (KPDX, KHIO, KVUO, KTTD, KUAO) with probabilities
for MVFR CIGs are 30-50% from 10-17z. At the coast, expect low
marine stratus with high- end IFR to low- end MVFR cigs to
persist at KAST through 20-22z Sunday. KONP has dropped to IFR
CIGs and will likely remain MVFR or IFR through around 18z
Sunday.

Diurnal west to northwest wind 5-10 kt, relaxing inland to
around 5 kt overnight.


PDX AND APPROACHES...VFR conditions expected through early
tonight. There is a 30-50% chance for sufficient stratus coverage
to yield MVFR cigs after 10-12z Sat before stratus mixes out by
18z Sat. North, northwest winds around 5 kt. -Batz/TK

&&

.MARINE...While winds remain weak across the waters, high
pressure will maintain northerly to northwesterly winds through
next week, however winds will remain relatively weak and should
stay under 10-15 kt. Seas should subside to 5 to 6 ft Friday
evening and then stay at or below 5 ft through the upcoming
week. There are no signs conditions will meet Small Craft
Advisory criteria over the coastal waters at this time. -TK

&&

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

&&

$$

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