510
FXUS66 KPQR 292148
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
248 PM PDT Thu Oct 29 2026

.SYNOPSIS...Cool and showery conditions continue through Friday
as an upper-level low sits offshore. Clear skies and calm winds
may bring frost development across much of NW OR and SW WA in
the mornings Saturday through Tuesday. Mostly dry conditions
return this Halloween weekend except along the OR Cascades.
High uncertainty for the return of precipitation early next
week with limited weather impacts expected.

&&

.DISCUSSION...through Wednesday...Scattered showers continue
across NW OR and SW WA Thursday afternoon. Some stronger showers
could produce heavy rain and small hail, and with SPC
mesoanalysis indicating CAPE values are around 100-250 J/kg this
afternoon, can`t rule out a lightning strike or two along the
far NW OR and SW WA coast through the early evening hours.
Scattered showers continue tonight into Friday as the center of
the upper level low pressure system causing the showers slowly
deepens along the WA coast. By late Friday into Saturday,
ensemble guidance is in good agreement that this low deepens and
tilts negatively enough for widespread precipitation chances to
lower below 10% except for along the OR Cascades and foothills
where shower chances increase Saturday afternoon and evening to
20-60%. The majority of NW OR and SW WA is expected to see dry
conditions for Halloween festivities, though daytime
temperatures in the low 50s could fall into the 40s by the
evening hours once the sun sets.

Skies are forecast to become more clear Friday night into early
Saturday, and winds will be nearly calm. This will allow for
temperatures to become quite chilly by Saturday morning. There`s
a 50-90% chance of frost across the majority of the forecast
area Saturday morning as well as a 50-85% chance of temperatures
below freezing for most inland valleys outside of the Portland
metro area. A combination of a Freeze Watch and Frost Advisories
have been issued for midnight to 9 AM on Saturday, including for
coastal locations off of the beaches. There are similar
probabilities for below freezing conditions Sunday and Monday
mornings, though probabilities are slightly lower on Sunday due
to uncertainty of cloud cover. However, freeze and frost
headlines are only issued during the growing season of April 1
through October 31. Therefore, no additional freeze or frost
headlines will be issued after Saturday.

Ensemble guidance is in good agreement that the upper level low
will finally push inland Saturday night, moving east of the
Cascades Sunday morning with ridging building over the PacNW
later Sunday into Monday as another closed low pressure system
forms in the eastern Pacific. Dry weather returns Sunday into
Monday with mostly sunny skies and the previously mentioned cold
mornings. By late Monday, ensemble members diverge on solutions
for the movement of the eastern Pacific low. Around half of the
members think the low will remain over the ocean early next week
with ridging remaining over the PacNW, keeping dry conditions.
The others indicate the low moving onshore somewhere over
central or northern California, though timing and north- south
extent differ, leading to uncertainty in weather precipitation
could return on the north side of the low. At this point, no
significant impacts are expected with the upcoming weather
pattern. -03

&&

.AVIATION...Through 00Z Saturday...Radar and surface weather
observations from 2045Z Thursday showed scattered rain showers
lingering over northwest OR and southwest WA. A mix of VFR/MVFR
ceilings were being observed, with VFR ceilings being most
predominant. Two exceptions include KHIO and KONP, as these sites
have been fluctuating between IFR and MVFR conditions. Expect
ceilings to continue fluctuating between flight categories through
Friday afternoon as periodic showers continue, however with
VFR/MVFR ceilings being most predominant. The strongest showers
that occur between now and 03Z Friday will have the potential to
produce brief heavy rain and small hail up to the size of peas.
Chances for ceilings below 3000 ft increase to 20-30% at most TAF
sites between 12-18Z Friday, with the highest chances for MVFR
ceilings with passing rain showers.

KPDX AND APPROACHES...Rain showers increase in coverage again
beginning around 21-22 Thursday. The strongest showers through 03Z
Friday will have the potential to produce brief heavy rain and
small hail up to the size of peas. Ceilings today and tonight
should be predominately VFR, but will occasionally drop to MVFR
thresholds with passing showers. Chances for ceilings below 3000
ft increase to 20-30% between 12-18Z Friday, with the highest
chances for MVFR ceilings with passing rain showers. -23

&&

.MARINE...Winds and seas will continue to subside this evening
through tonight, resulting in relatively benign conditions. One
exception is over the main channel of the Columbia River Bar with
a very strong ebb current Thursday evening, which will temporarily
push seas up to around 8 ft. As such, a Small Craft Advisory
remains in effect for the Columbia River Bar from 5-9 PM PDT Thursday.

South winds increase over the waters on Friday, but should
generally stay under 20 kt, except over the northern inner waters
and the main channel of the Columbia River Bar where gusts will
likely top out near 20-21 kt. Winds weaken again over the weekend
with seas hovering near 4 to 5 ft.

Monday and Tuesday are highlighted by light offshore winds with
seas building to 8-11 ft with the arrival of a long period west-
northwest swell with a dominant wave period of 15-17 seconds.
Given winds will be relatively light, seas will be primarily
driven by the long-period swell rather than wind waves. Chances
for seas over 10 ft on Monday have increased to 40-60% over the
outer waters and 15-30% over the inner waters. -23

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Frost Advisory from midnight Friday night to 9 AM PDT Saturday
     for ORZ101>103-107-108-111>113-119-124-125.

     Freeze Watch from late Friday night through Saturday morning for
     ORZ105-109-114-115-123.

WA...Frost Advisory from midnight Friday night to 9 AM PDT Saturday
     for WAZ203-204-206-207.

     Freeze Watch from late Friday night through Saturday morning for
     WAZ205.

PZ...Small Craft Advisory from 5 PM this afternoon to 10 PM PDT this
     evening for PZZ210.

&&

$$

www.weather.gov/portland

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