090
FXUS66 KPQR 311047
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
347 AM PDT Fri Jul 31 2026

.SYNOPSIS...A progressive weather pattern with prevailing
onshore flow continues through the weekend. Broad southwest
flow aloft will allow temperatures to peak in the mid to upper
80s today before a frontal system slated for Saturday ushers in
cooler temperatures, chances for light rain, and locally gusty
west winds over the weekend. Wind related impacts are highest
in the central Columbia Gorge. Trailing this frontal system, a
broad pattern change favoring warmer and drier weather is
expected by the middle of next week with a period of northerly
to northeasterly winds as well - a combination we`ll have to
watch closely.

&&

.SHORT TERM...Now through Saturday Night...The Pacific Northwest
remains on the western periphery of a building ridge of high
pressure today as an upper-level low looms over the
northeastern Pacific. Still, the influence of the ridge just to
our east and broad southwesterly flow aloft will allow for
temperatures to jump day to day with high confidence in
afternoon temperatures reaching into the mid to upper 80s across
the Willamette Valley, Portland Metro, southwest Washington,
and other inland valleys. The two former areas have at least a
decent shot at maxing out around 90 degrees too (20-45% chance).
While these temperatures will be warmer than the last several
days, we are not expecting any record breaking heat but rather
just slightly above normal and rather temporary in the context
of what is expected this weekend.

On Saturday our focus shifts to the aforementioned upper-level
low over the northeastern Pacific which as it tracks into
British Columbia swings a weak cold front into the region to
start the weekend. Beyond causing temperatures to lower, the
tightening surface pressure gradient across the Cascades forces
west winds to increase significantly for some select locations.
These areas include the Upper Hood River Valley, Columbia River
Gorge, and gaps in the Coast Range. If we look at the NBM 90th
percentile (10% chance of occurring), gusts could reach as high
as 45 mph in Hood River and the more exposed terrain in the
Central Gorge. For the Willamette Valley, there is a 10% chance
of gusts up to 25 mph but based on the wind direction, for most
areas this may be a bit overdone. In addition to the wind, light
rain is expected with the frontal passage though accumulation
will be minimal, generally less than 0.05-0.10in for the vast
majority of locations, if you even see anything at all. Overall
looking at high confidence (>80%) for the north coastal areas
for accumulating light rain, 30-60% for southwest Washington,
and less than 10% for most of the interior portions of Oregon.
-99/27

.LONG TERM...Sunday through Thursday...The broader upper-level
low feature passing to our north continues to influence the
region on Sunday with similarly cool conditions overall compared
to the start of the weekend - very little in the way of weather
related impacts. However, Monday and Tuesday will see more
change. Early next week the progressive upper trough exits
eastward while a ridge of high pressure amplifies over the
eastern Pacific and Four Corners region. It`s around this point
deterministic and ensemble systems begin to show growing
deviations in the upper-level pattern going forward which leads
to higher forecast uncertainty by the middle of the week. While
temperatures are very likely to be warmer compared to the
weekend, the spread of potential solutions remains somewhat
broad, especially on Wednesday. At this point, there is an
80-90%+ chance of highs in the 80s within inland valleys on
Monday and a 75-80% chance of meeting of exceeding 90 on
Tuesday. Mid to late week it`ll all come down to the exact pattern
amplification and longitudinal placement of the ridge over the
far eastern Pacific. In the warmer solutions (favored by GFS and
more GEFS members), stronger inland ridging and the resulting
coastal thermal trough may be sufficient to drive decent
offshore flow and potential gusty north to northeast winds
along the coast and within the Willamette Valley. The EPS keeps
this ridge flattened comparatively but still shows a signal for
north to northeast winds, albeit weaker. At least the bulk of
deterministic and ensemble guidance depict a return to W-NW
winds by late Thursday signaling moderating conditions.

From a fire weather prospective the pattern early to mid week
does raise some concerns, especially on Tuesday, as notable
N-NE winds during the afternoon hours and minimum relative
humidity values below 25% could combine for a period of elevated
to critical fire weather conditions in the central and southern
Willamette Valley (a 30-50% chance according to the latest
NBM). Much of this hinges on the placement/strength of the ridge
axis and accompanying near surface thermal trough over
southwest Oregon as mentioned earlier. Additionally, the weak
offshore component to the low to mid level flow (surface to
700mb) has the potential to adversely impact overnight humidity
recoveries in the Cascades, adjacent foothills, and tops of the
coast range. We`ll have to watch this late Monday through
Wednesday period closely the next several forecast cycles as
models converge on a solution and forecast confidence increases.
-99

&&

.AVIATION...Through 12Z Saturday...Current satellite and surface
observations early this morning show widespread VFR conditions
across the region as coastal stratus hangs off the coastline.
There`s only a 10-20% chance for degraded flight conditions at
KONP/KAST prior to 16-17z, after which point VFR conditions are
favored through most of the daytime hours. That said, a westerly
surge of low stratus late day (after 23z) likely leads to MVFR
CIGs/VIS or lower along the coast by the evening hours. Otherwise,
VFR conditions are heavily favored at all inland sites through the
TAF period.

KPDX AND APPROACHES...Expect VFR conditions with mostly clear
skies and northwest winds generally less than 5-10 kts through
the TAF period. -99

&&

.MARINE...Fairly benign conditions continue across the waters today
as winds remain out of the W-NW. Headed into the first half of the
weekend a frontal system approaching the waters brings increasing
winds, mainly for the outer waters and the inner waters north of
Cape Falcon. Chances for rain peak Saturday morning during the
frontal passage, likely dissipating during the afternoon hours.

Behind the boundary, initial westerly flow will veer out of the
north by Sunday as surface high pressure builds offshore. Chances
for maximum wind gusts of at least 21 kt are around 70-90% from
Sunday afternoon/evening through at least Tuesday evening -
highest probabilities outer waters. We`ll still have to watch for
a period of marginal Gale Force northerly winds late Monday
afternoon (5-25% chance south of Cape Foulweather). Wave heights
through this time period remain around 5-7 ft at 7-9 seconds.
-99/12

&&

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

$$

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