018
FXUS66 KPQR 040619 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1018 PM PST Mon Nov 3 2025

...Updated aviation discussion...

.SYNOPSIS...Rain continues across much of the area through this
evening as an axis of moisture remains in place from the central
Oregon coast to the south Washington Cascades. A compact surface low
will move onshore near the central Oregon coast later this evening
potentially bringing brief gusty winds from Florence to Newport and
into the southern Willamette Valley. Trending drier on Tuesday
before a warm front lifts north across the area later Tuesday
afternoon and evening. The active weather pattern returns by Tuesday
night as a strong low pressure system develops offshore and sends a
series of fronts across the area. Expect widespread rain and gusty
winds with each frontal passage, though high winds not expected at
this time. There is also around a 15-30% chance of thunderstorms on
Wednesday, highest at the coast. In addition, minor tidal overflow
flooding is expected along portions of Highway 101 and Fraser Road
in Tillamook County around high tide on Wednesday from 10 AM to 3 PM
PST. Conditions likely trend drier late Friday into Saturday.

&&

.SHORT TERM...Tonight through Wednesday night...A frontal band
draped across much of NW Oregon into SW Washington is producing
light to moderate rain across the area this afternoon. Rain is
expected to continue through this evening as an upper shortwave
trough approaches the region and an associated surface low moves
northeast toward the central Oregon coast. The heavier rainfall is
expected to occur within a band from Florence to Rockaway Beach
northwestward into the south Washington Cascades, where total
rainfall amounts are likely to exceed 0.5 inch, with locally higher
amounts within the terrain of the Coast Range and Cascades,
including much of the western Columbia River Gorge, where there is
around a 20-40% chance of exceeding 2 inches.

This compact meso-low will also be accompanied by gusty southerly
winds, but there still remains a bit of uncertainty as to where
exactly the low will move onshore. The latest HREF and REFS guidance
shows wind gusts this evening potentially reaching 40-50 mph along
the central Oregon coast and maxing out around 30-40 mph across the
southern Willamette Valley. A few of the individual hi-res models
(including the HRRR) show this low pushing farther north with
southerly wind gusts reaching the Portland metro around midnight,
while others (e.g. UWWRF) keep the low much farther south, pushing
inland near Florence with much lighter winds across the area. Will
forgo any wind headlines as there is generally a 10% chance or less
for even the highest winds to come to fruition.

A few lingering light showers possible early Tuesday morning, but
expect a break in the rain with drier conditions persisting into
Tuesday afternoon as a transient upper level ridge moves over the
region. But, the next frontal system will be quickly approaching
from the south as a warm front lifts across western Oregon later
Tuesday afternoon and evening. On Wednesday, a negatively tilted
upper level trough approaching the western US will push into the
Pacific NW sending a cold front across the area. Snow level are only
expected to fall to around 5500-6000 ft, so not anticipating any
snow at pass levels. But expecting plenty of rainfall through
Wednesday night, though the majority of the energy and moisture will
likely be directed toward the southern Oregon coast. IVT values in
NW Oregon are likely to peak around 750 kg/m/s at the coast and
around 500 kg/m/s over the Cascade foothills, overall presenting a
moderate Atmospheric River with precipitable water (PWAT) amounts
maxing out at around 1.2 inch for Tuesday night. That said, rainfall
amounts for this system are expected to be highest along south to
southwest facing slopes as much of the moisture transport will be
from this direction.

Another round of breezy winds is expected on Wednesday, turning from
southeasterly to southwesterly as the front pushes through. Latest
guidance suggests around a 20-40% chance of wind gusts exceeding 55
mph along the coast, while there is around a 20-30% chance of wind
gusts exceeding 45 mph (Wind Advisory criteria) through the southern
and central Willamette Valley. Most likely will see wind gusts
around 30-40 mph inland and 45-50 mph at the coast, with gusts up to
55 mph along beaches and headlands. This would be strong enough to
result in some tree damage and power outages, but would not be
strong enough for widespread downed trees and significant impacts.

Showers are expected to continue behind the frontal passage on
Wednesday with an unstable air mass developing across the area
through Wed evening, leading to a 15-30% chance of thunderstorms,
highest chances at the coast. Latest RAP guidance shows around 300-
500 J/kg of "skinny" CAPE, with 150-250 m2/s2 of 0-3 km wind shear.
Depending on the timing of this front, a few of these stronger
showers or thunderstorms could produce strong winds and small hail,
along with a low chance of funnel clouds.

.LONG TERM...Thursday through Sunday...The next system is expected
to move into the region on Thursday, bringing another round of rain
and gusty winds. Wind speeds with this front look to be fairly
similar to Wednesday. This frontal system is also on track to
produce similar rainfall amounts. WPC QPF amounts from 4am Thursday
through 4am Friday range between 1.0-1.2 inches for inland valleys,
1.5-2.0 inches for the coast and Cascade foothills, and 2-3 inches
for the Coast Range and south WA/north OR Cascades. Given all the
rain that is forecast to fall prior to the system on Thursday,
rising river levels will be a concern. The main question that
remains is whether or not enough rain will fall for some rivers to
reach flood stage on Wednesday and/or Thursday. According to the
latest HEFS guidance, the probability for any given river to reach
minor flood stage is generally 10% or less, except a 15% chance for
the Wilson River near Tillamook. Another river of concern would be
the Grays River near Rosburg. Small creeks and streams are more
likely to see some minor flooding. Lastly, minor urban flooding will
also be possible, especially in low-lying areas with poor drainage.

Rain chances remain in the forecast Friday, however ensemble
guidance suggests rain amounts will be lighter and less impactful.
WPC 500 mb cluster analysis also shows increasing chances for upper
level ridging to build over the region, with 61% of ensemble members
putting the ridge axis over the Pacific NW, which would keep the
area mostly dry on Saturday. Lower probabilities for upper troughing
remaining over the area (15%). An increasing number of ensemble
members do bring rain back into the forecast on Sunday as deep
troughing offshore pushes the upper level ridge east toward the
Rockies.

&&

.AVIATION...A weak low pressure system is bringing widespread rain
across northwest Oregon as of late Monday evening. This low is
quickly progressing eastward and weakening, so expect rain to
decrease by 07-08z Tue. Expect predominately MVFR CIGs across the
area (>80% chance) until around 12z Tue. Winds will generally be
light and offshore as the surface low creates offshore pressure
gradients. After 12z Tue, CIGs should begin improving to
predominately VFR. The next strong low pressure system approaches
Tuesday afternoon, with rain progressing from south to north after
21z Tue. At this point, guidance suggests CIGs will remain low- end
VFR. Expect easterly to northeasterly winds as offshore pressure
gradients continue.

KPDX AND APPROACHES...Rain should begin to diminish after 07-08z
Tue. 40-60% chance for MVFR CIGs through 12z Tue. CIGs gradually
improve to VFR throughout the morning. Rain arrives after 22-23z Tue
from the south, with low-end VFR CIGs. Easterly winds gradually
increase throughout the day with gusts up to 20 kt as offshore
pressure gradients tighten.     -10

&&

.MARINE...Seas remain steep with heights in the low teens and a
period of 13 to 15 seconds. A Small Craft Advisory remains in
effect for all zones through 4 pm. Seas will then fall to 8-9
feet at 12-13 seconds through Tuesday. A compact surface low will
track northeast toward the central Oregon coast this evening,
bringing localized gusty winds to the waters off of the central
Oregon coast. Guidance suggests winds will increase for the outer
and inner southern waters (PZZ273-253) along with the central
inner waters (PZZ252) with southerly winds 15 to 20 kt and gusts
to around 25-30 kt. Isolated wind gusts to 35-40 kt possible but
not expected to be persistent. A Small Craft Advisory remains in
effect through 4 AM Tuesday.

An active pattern for all waters will return by mid week as
several strong systems are set to bring Gale and possibly Storm
force conditions. NBM 24 hour probabilities for winds to reach
Gale criteria are 95+% for the outer waters late Tuesday,
spreading to all waters Wednesday and Thursday. The probability of
Storm force winds during the same time period start out at 30-60%
for the outer waters, mainly in zone PZZ273, late Tuesday and
spreads to all waters Wednesday and Thursday. At this point, not
expected Storm force winds to be widespread enough for a hazard,
so a Gale Warning has been issued for 2 pm Tuesday through 7 pm
Wednesday. Seas are also expected to increase, with mainly wind
driven seas pushing into the mid to upper teens by Wednesday and
lasting into Thursday. Guidance currently suggests a 5-15% chance
that seas will exceed 20 ft. There is still plenty of uncertainty
in exact details but the active pattern is expected to persist.
-03

&&

.BEACH HAZARDS...There is a Coastal Flood Advisory for minor
tidal overflow flooding during high tide from 10 AM to 3 PM
Wednesday for the Pacific County Coast, Clatsop County Coast, and
Tillamook County Coast. Minor flooding during high tide is
expected in the low lying areas near bays, sloughs, and the lower
reaches of the coastal rivers. This is due to total tide up to 12
feet at Toke point resulting in tide up to one foot above ground
level, total tide up to 11 feet at Tongue Point resulting in tide
up to one foot above ground level, and total tide up to 11 feet
at Garibaldi resulting in tide up to one foot above ground level.

Expect flooding along portions of Highway 101, including near
Raymond, Seaside, and Fraser Road in Tillamook County. Coastal
residents in the warned area should be alert for rising water and
take appropriate action to protect life and property. Remain out
of the water to avoid hazardous swimming conditions.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Coastal Flood Advisory from 10 AM to 3 PM PST Wednesday for
     ORZ101-102.

WA...Coastal Flood Advisory from 10 AM to 3 PM PST Wednesday for
     WAZ201.

PZ...Small Craft Advisory until 4 PM PST this afternoon for PZZ210-
     251-271-272.

     Gale Warning from 7 PM Tuesday to 7 PM PST Wednesday for PZZ210-
     251>253.

     Small Craft Advisory until 4 AM PST Tuesday for PZZ252-253-273.

     Gale Warning from 1 PM Tuesday to 7 PM PST Wednesday for
     PZZ271>273.
&&

$$

www.weather.gov/portland

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