932
FXUS66 KPQR 282100
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
200 PM PDT Mon Sep 28 2026

.SYNOPSIS...Dry weather continues through this evening, but expect
sunny skies to give way to increasing clouds as a frontal system
approaches from the north. On Tuesday, this decaying frontal system
drops south across northern portions of the area bringing chances
for rain through late Tue night, with the highest probabilities
along the Washington and north Oregon coast and Coast Range. Dry
weather is favored again by Wednesday with temperatures trending
warmer this weekend.

&&

.DISCUSSION...Now through Monday...Satellite imagery shows mostly
clear skies over the forecast area early this afternoon. But, mid to
high level clouds are expected to increase through tonight as a
weather system to the north gradually shifts southward. The weak
ridge of high pressure over the area will be replaced by zonal flow
over the region. With increasing cloud cover, do not expect
overnight temperatures to cool as much as this morning`s lows.

A decent plume of moisture associated with the frontal system is
currently impacting Vancouver Island, but is expected to weaken as
it drops south into western Washington as upper level support
quickly moves eastward across Canada. But, there appears to be
enough lingering moisture to bring some rain to the north Oregon
coast and possibly into the Portland Metro area and locations
northward. Latest guidance suggests there is around a 40-60% chance
for 0.25 inch of rainfall from Tillamook northward, with about a 50%
chance for a half inch of rain in the Willapa Hills. Rain will
likely be more spotty with light amounts expected across portions of
southwest WA and the Portland metro, generally less than 25% chance
for exceeding 0.10 inch, while conditions Salem southward remaining
dry.

Widespread dry conditions return by Wednesday morning, and likely
continuing through the remainder of the week into the weekend. The
one caveat includes a weak weather system potentially clipping
northern portions of our forecast area again Thursday into Friday.
But, most ensemble members are pushing the system farther north,
with only 10% or less showing rain. Temperatures remain fairly
seasonable through the end of September.

By the weekend, models and their ensembles are in fairly good
agreement of a more pronounced ridge of high pressure building over
the region. This would maintain dry weather and potentially trend
afternoon temperatures around 5-10 degrees above normal for early
October. Clusters hint at more uncertainty though heading into early
next week.  /DH

&&

.AVIATION...Through 18Z Tuesday...Northwest flow aloft becomes
westerly on Tuesday as high pressure gradually weakens over the
area. Predominately VFR conditions expected today with increasing
high level clouds. Stratus is likely to return to the coast by
00-03z Tuesday as a weak front begins pushing into southwest WA.
Chances for light rain increase after 09-12z near KAST as
conditions likely to deteriorate to lower MVFR along with a 40-50%
chance of IFR conditions after 15z Tuesday. Chances for IFR near
KONP also increase to around 40-50% by 10-12z Tue. CIGs are also
expected to lower inland Tuesday morning, with around a 30-50%
chance of MVFR after 16z Tue, mainly north of KSLE. Winds increase
slightly along the coast to around 6-10 kt from the west, turning
southerly by this evening and overnight.

KPDX AND APPROACHES...VFR conditions are expected through at least
15z Tuesday. Stratus likely increases Tue morning with lowering
CIGs, and around a 30-50% chance of MVFR after 16z Tue. Light
winds become southerly 4-6 kt Tue morning. /DH

&&

.MARINE...High pressure will continue to weaken as a frontal
boundary approaches the coastal waters tonight. Southerly winds
are expected to increase overnight into Tuesday morning with gusts
most likely peaking around 25-30 kt, strongest across the inner
waters north of Cape Falcon. A Small Craft Advisory is in effect
for coastal waters north of Cape Foulweather, including the
Columbia River Bar where a strong ebb current is expected this
evening. Winds are expected to abruptly shift to the northwest
behind the cold front as is moves across the waters later Tue
afternoon and evening. Once the front passes, northerly winds
return Tuesday night through the middle of the week. Another weak
system may approach the northern waters from the west on Thursday,
but likely remains north as it moves toward the Washington coast.

A mid-period west-northwesterly swell of 6 to 8 ft at 13-15
seconds will move through the coastal waters today through Tue
night, increasing significant wave heights into the 8 to 10 ft
range. Seas then gradually subside to around 4 to 6 ft later in
the week. /DH

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 5 PM this afternoon to 5 PM PDT
     Tuesday for PZZ210.

     Small Craft Advisory from 8 PM this evening to 5 PM PDT Tuesday
     for PZZ251-271.

     Small Craft Advisory from 5 AM to 5 PM PDT Tuesday for PZZ252-
     272.
&&

$$

www.weather.gov/portland

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