248
FXUS66 KPQR 011740 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1040 AM PDT Thu Oct 1 2026

Updated Aviation Discussion...

.SYNOPSIS...Dry weather persists going forward accompanied by a
warming trend into the weekend as a ridge of high pressure
builds overhead - well above normal temperatures by Sat/Sun.
Expect patchy morning fog at times across inland valleys as
well, although offshore winds develop Saturday and Sunday may
limit the coverage of fog somewhat. Otherwise, little in the
way of weather impacts through at least the middle of next week.

&&

.DISCUSSION...Now through Wednesday...Our dry streak continues
for at least the next week as a above normal temperatures
become a common theme to start October. At least for today
however, a weak weather system is expected to brush the Pacific
Northwest to the north near Vancouver Island helping to keep
the ridge flatter than it otherwise would be while also
streaming high clouds across the region from time to time. 850
mb temperatures warm several degrees compared to yesterday
(Wednesday) which will in turn allow afternoon highs to warm
into the mid to upper 70s across the interior lowlands today.
The NBM even gives portions of the Willamette Valley a 10-30%
chance to exceed 80 degrees, the first of many increasing
chances to pass this threshold as we move onward into the
weekend.

Expect temperatures to jump a few more degrees Friday and
especially Saturday/Sunday as the upper level ridge amplifies
over the Pacific NW along with mostly sunny skies each
afternoon. Temperatures likely warm into the upper 70s to lower
80s on Saturday before warming a few more degrees, into the
lower to mid-80s on Sunday. Most areas are not expected to reach
record high temps, but the record of 84 degrees on Sunday at
PDX could be in jeopardy. Offshore flow could also bring
slightly warmer temperatures to the coast as well with highs
into the upper 60s to lower 70s.

Throughout the end of the week into the weekend the combination
of overnight clearing/longer nights, locally lighter winds, and
a fairly prominent temperature inversion will facilitate fog
development. But, the placement of valley fog likely shifts to
some of our more protected valley areas over the weekend as the
previously mentioned offshore flow develops - this is a point of
notable forecast uncertainty. Should the overnight offshore
flow/east winds end up weaker or decoupled from the boundary
layer over the Willamette valley, fog end up fairly decent in
coverage. The REFS and even the ECMWF points to this foggier
scenario playing out at least on Saturday morning. Wherever
present, fog will greatly reduce visibility and may potentially
impact travel.

Underneath this upper-level ridge pattern over the next several
days, ensembles indicate a near surface thermal trough develops
along the coast on Friday through this weekend. This pattern is
expected to cause winds to shift from the onshore (westerly)
pattern the area has generally been observing over the past
couple of weeks to offshore (east to northeasterly). At this
time, pressure gradients do not look to be very high, peaking at
a -3mb to -4mb difference between PDX and DLS, so winds aren`t
expected to be strong. Instead, expect to see a typical diurnal
behavior of winds becoming easterly on the west side of terrain
(mainly Cascades, potentially tops of the coast range as well)
during the overnight to morning hours, increasing to peak gusts
up to 20-35 mph. Then, as mixing gets underway and the inversion
breaks, winds decrease over the terrain during the day and
increase through the valley from the north in the afternoon
hours with gusts up to 20 mph. Exploring the NBM, the
probability of wind gusts peaking above 30 mph is less than
10-25% everywhere except in the western Columbia River Gorge and
surrounding terrain at 40-55%, which is generally the windiest
location during offshore easterly flow.

By Monday, the vast majority of ensemble members indicate the ridge
axis shifts east of WA and OR, allowing the overall flow to
turn back onshore while bringing an end to the locally breezier
east winds. Temperatures lower again into the 70s to near 80
for the interior valleys Monday afternoon into the middle of the
week, though we`ll remain generally 5 to 10 above normal for
early October. For better or worse, ensemble guidance is adamant
in the continuation of dry weather through the middle of next
week, potentially longer. -99/DH

&&

.AVIATION...Through 18Z Friday...High pressure over the region
brings widespread VFR conditions with high clouds, expected to
continue through at least 12Z Fri. After 12Z Friday, chances of
deteriorated conditions increase throughout the airspace.
Specifically, chances at KAST and KONP are around 20% for LIFR,
30% for IFR, and 40-50% for MVFR after 12Z Fri. As for inland
terminals, chances are around 10-15% for LIFR, 20% for IFR, and
30% for MVFR after 12Z Fri. While such conditions will consist of
CIGs and VIS, CIGs are more likely. Otherwise, light and variable
winds will become north/northwesterly winds of 5-10 kt by this
afternoon, strongest at KONP, KSLE, and KEUG.

KPDX AND APPROACHES...VFR with high clouds and north-northwesterly
winds 3-6 kt through the TAF period. ~12

&&

.MARINE...We`ll see the continuation of calmer weather today as a
weak weather system brushes the waters to the north, temporarily
shifting winds out of the west around Cape Falcon northward.
Northerly winds then return across the entire waters Friday,
likely persisting through the weekend into early next week. Wind
gusts generally rise in the 10-20 knot range through this period.
Otherwise, the west to northwesterly swell of ~6 ft at 9 to 11
seconds gradually subside to around 3 to 5 ft at 8 to 9 seconds by
Friday into the weekend. At this time, there are no other
prominent swells of note through at least the the middle of next
week. -99/12

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

www.weather.gov/portland

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