906
FXUS66 KPQR 240525 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1025 PM PDT Fri Oct 23 2026

Updated Aviation Discussion...

.SYNOPSIS...Dry weather is expected through Saturday with
overnight and early morning frost/freeze conditions across
much of the region. Rain chances increase early Sunday morning,
then linger into the beginning of the workweek. The active
pattern continues with additional rain chances midweek.

&&

.DISCUSSION...Now through Friday...Transient upper-level ridging
continues to build overhead, bringing clearing skies to the
region. Cool temperatures aloft will support seasonable daytime
highs in the 50s on the coast and in terrain and in the low to
mid 60s within inland valleys. As the ridge axis shifts inland,
light offshore flow will peak overnight in the Cascades and
Coast Range. Clear and calmer valley conditions will again yield
efficient nocturnal radiative cooling, with Saturday morning
likely to be the coldest. Widespread morning lows in the 30s are
expected, coldest in sheltered valleys including the southern
Willamette and neighboring peripheral valleys, northern Coast
Range valleys near Vernonia and Grand Ronde, and the Upper Hood
River Valley, where Freeze Warnings are in effect from 11 PM PDT
this evening through 10 AM PDT Saturday. Frost Advisories for
temperatures in the low to mid 30s are in effect at the same
times for most other areas outside of the south Washington coast
and coastal lowlands. Those with exposed or uninsulated outdoor
pipes, agricultural interests, or sensitive outdoor plant
should take action to prevent frost/freeze damage tonight.

Seasonable conditions with milder overnight temperatures then
persist through the remainder of the period as the weather
pattern becomes more active by late this weekend. Mean upper
troughing develops over the region from Sunday through much of
next week as a series of upper lows drop from the Gulf of Alaska
over the Pacific Northwest. There remains good agreement among
mid-range ensembles that an initial system will move into the
region on Sunday with rain beginning at the coast early Sunday
morning and reaching inland through the afternoon, although
there are modest, perhaps 10-20% chances, that the system tracks
farther to the south with lower rain chances locally. As the low
slowly exits eastward,  At this point, the chances for 0.25
inches of rain or more from 5 AM Sunday through 5 AM Tuesday are
75-85% along the coast and Coast Range, 60-75% along the I-5
corridor, and 50-60% in the Cascades and foothills.

Forecast confidence decreases by midweek as this low departs
eastward, although long-range guidance does continue to support
additional chances for rain, with 30-40% of ensemble members
bringing another weather system to the Northeast Pacific.
Otherwise, seasonable temperatures are favored to continue into
the final week of October. -36

&&

.AVIATION...Through 06Z Sunday...Current widespread VFR
conditions at coastal and inland terminals will likely continue
through the TAF period. With skies expected to remain clear
through at least 12Z Saturday, there is the potential for frost
or fog at inland terminals, generally in the southern Willamette
Valley. Guidance suggests a 15 to 25% chance of LIFR conditions
between 08-16Z Saturday, with the highest chances at KHIO and
KEUG. With these chances competing with frost potential tonight,
confidence is too low to include broken or overnight low status in
the TAFs, although isolated pockets of fog and low stratus in
valleys cannot be ruled out. Expect winds to remain light and
variable through most of the period at all terminals.


KPDX AND APPROACHES...VFR conditions will continue through the TAF
period with light and variable winds around 3 to 5 kt. Frost
development is possible tonight into early tomorrow morning as
temperatures dip as low as 35-38 degrees. If temperatures do not
drop low enough, there is a 15% chance of low stratus/fog
between 12-17Z Sat.  ~12

&&

.MARINE...Seas continue to decrease tonight into Saturday, well
below 10 ft. Winds remain weak and continue to decrease into
Saturday. A slow-moving low will approach the outer waters late
Saturday into Sunday, bringing a transition to southerly winds
with seas increasing again Saturday night into Sunday. Conditions
will be hazardous for small craft during that time, before winds
and seas decrease early next week. There is still uncertainty on
the exact strength and track of this low, however probabilities
for gale force wind gusts remain low at 5-15%, except 25-35% near
buoy 029. Chances for seas over 10 ft peak between 15-35% Sunday
morning, with the highest probabilities beyond 20-30 NM offshore.
-23

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Frost Advisory until 10 AM PDT Saturday for ORZ101>103-105-
     107>109-111>113-119-123.

     Freeze Warning until 10 AM PDT Saturday for ORZ104-106-114>118-
     124-125.

WA...Frost Advisory until 10 AM PDT Saturday for WAZ203>208.

PZ...None.

&&

$$

www.weather.gov/portland

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