091
FXUS66 KPQR 172100
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
200 PM PDT Sun Aug 17 2025

.SYNOPSIS...High pressure continues to build over the region
through the week. Persistent onshore flow will help to mitigate
daytime highs through the middle of the week. However, a
strengthening upper level ridge towards the latter part of the
week will bring about warmer temperatures as well as weak
offshore flow.

&&

.SHORT TERM...Now through Wednesday Night...Models are showing
little deviation from run to run through Wednesday with a
general warming and drying trend across the CWA. The synoptic
pattern is composed of a broad area of low pressure within the
the northeast Pacific, and a developing high over the
Rockies/Great Basin. Through Wednesday, the Pacific low looks to
remain anchored over the panhandle of Alaska and the islands of
British Columbia through Monday. The low will generally keep
southwesterly flow aloft with northwesterly flow at the surface.
It should be noted that some models are bringing very light
precipitation/aggressive drizzle to the coast Monday and
Tuesday, most models are keeping precipitation well off the
OR/WA coast. The southwesterly flow aloft and northwesterly flow
at the surface, will help to mitigate daytime highs. Daytime
highs Monday and Tuesday look to be in the upper 70s to low 80s
and overnight lows in the low 50s to upper 50s. Overall,
temperatures are expected to be around normal to slightly above
normal through Tuesday.

As Tuesday becomes Wednesday, a pattern change is on the
horizon. The upper level Alaskan low looks to develop a broad
trough or cutoff low (depending on model) that will be drug
eastward with the parent low. This will result in a deformation
in the Rockie/Great Basin High and as a result, 850 mb
temperatures will rise through through Wednesday. While a slight
difference in both daytime highs and overnight lows are
expected. A significant change in temperatures will be noticed
for the latter part of this week. /42

.LONG TERM...Thursday through Saturday...As we move into the
latter part of the week and weekend, the Rockie/Great Basin
ridge looks to rebound and push further eastward. Zooming out,
a weak, upper level Omega blocking pattern looks to form. The
Great Basin high will be the center with a robust low over the
Great Lakes and a weaker low around the Alaskan Panhandle. Now,
with a broad area of high pressure impacting western Oregon, the
surface looks to develop a thermally induced trough which would
bring some offshore flow to the CWA. Thursday through Saturday,
850 mb temperatures will slowly rise from 15-17 deg C on
Thursday towards 21-23 deg C Friday and Saturday. This will
maintain a warming a drying trend through the forecast period
with the highest daytime highs in the low to mid 90s Friday and
Saturday, with Friday likely to be the warmest this week. /42

&&

.AVIATION...Largely VFR flying conditions expected across the
region, with sct-bkn clouds at 4-6 kft through this afternoon and
evening. Along the coast, a few isolated rain showers cannot be
ruled out, most likely at KAST, but any impacts are unlikely and
would be brief. Marine stratus this evening into tonight will
favor IFR/LIFR cigs and potentially restricted vis after 00-06z
Mon at coastal terminals, most widespread along the central Oregon
coast with lower confidence to the north. Inland, VFR conditions
are expected to continue, however there remains a 10-20% chance of
cigs falling to MVFR levels after 12z Mon. West to northwest
winds of 5-10 kt this afternoon will ease to 5 kt or less out of
the south to southwest overnight, then build to 5-10 kt out of
the southwest along the coast and west to northwest inland by
Monday afternoon.

PDX AND APPROACHES...VFR flying conditions are expected with
persistent sct-bkn low clouds at 5-6 kft and bkn high clouds at
or above 25 kft. Low cloud cover again increases tonight, with a
10% chance of MVFR cigs from 12-18z Mon. Northwest winds around 5
kt will become light and variable after 06-09z Mon, then increase
to around 5 kt out of the northwest by 18z Mon. -Picard

&&

.MARINE...Relatively tranquil conditions are expected through at
least midweek with light southerly to southwesterly winds and
seas falling from 5-7 ft today to 3-5 ft by Tuesday, driven
largely by a subsiding west-northwesterly swell at 9-10 seconds.
High pressure building over the northeastern Pacific will see
winds shift out of the northwest to north by Tuesday night, with a
60-80% chance of gusts exceeding 20 kt on Wednesday south of Cape
Falcon and 30-60% chances to the north. The amplifying ridge will
further increase chances for 20 kt gusts to 70% or more across
the waters on Thursday and Friday. -Picard/HEC

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

www.weather.gov/portland

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