151 
FXUS66 KPQR 021822 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1022 AM PST Tue Dec 2 2025

Updated aviation discussion. 

&&

.SYNOPSIS...Cloudy, with a few sprinkles today. High pressure 
nudges into the region later tonight with dry conditions 
expected on Wednesday. A series of fronts will bring a wet 
period of weather later this week into the weekend across 
southwest Washington and northwest Oregon with potentially more 
impactful rain next week.

&&

.DISCUSSION...Water vapor satellite imagery this morning shows an 
upper trough digging across the Pacific Northwest. A weak front is 
pushing across northwest Oregon and southwest Washington today, and 
will ultimately fall apart as it pushes farther south. This will 
maintain cloudy conditions with scattered sprinkles to light rain 
showers into this afternoon. Light north to northeasterly flow 
spreads across the region late this afternoon into tonight. This may 
result in just enough clearing to allow fog and low clouds to 
redevelop overnight across inland valleys. The flow will turn more 
northwesterly Wednesday and open us to weak shortwave troughs that 
could bring light precipitation to mainly our far northern zones and 
terrain late Wednesday into early Thursday.  

Models and their ensembles are in good agreement that the upper
level ridge remains over the northeast Pacific on Thursday. WPC
cluster analysis does indicate there is a high probability of 
the ridge flattening out, allowing for more westerly flow into 
the Pacific NW Friday and into the weekend. This should allow for 
frontal systems and attendant weak atmospheric rivers to bring 
increased rainfall and more active weather to the area. Ensembles 
are in relatively good agreement, a weak to moderate strength 
atmospheric river will spread into the region Friday into early 
Saturday bringing with it mainly beneficial rains to the region.
The EC EFI does suggest some notable rainfall amounts will 
occur across the Oregon Cascades and foothills Friday night 
into Saturday relative to model climatology, but raw ensemble 
rainfall amounts appear unlikely to produce impacts with this 
first round of rain. With that said, there are handful of the 100 
global ensemble members that produce enough rain that our flashiest 
rivers would rise sharply and approach minor flood stage Friday 
into Saturday, but at this point, confidence remains low in 
this scenario panning out based on available ensemble guidance. 

Additional rounds of rain will continue for the remainder of 
the weekend as ensembles are in general agreement we will remain
under zonal flow in the vicinity of the baroclinic zone. Given 
the westerly flow there will likely be periods where the 
Willamette Valley rain-shadows out, but it may be raining, at 
least lightly, for a significant portion of the weekend across 
the terrain, particularly areas farther north in the CWA. 
Uncertainty in the forecast details grow significantly early 
next week and mainly revolve around whether or not a stronger 
atmospheric river with potential impacts to area rivers will impact 
the region or not. HEFS guidance does suggest a 10-15% chance for 
rivers like the Willapa, Naselle and Wilson Rivers to reach minor 
flood stage at some point in the next 10 days with that day 8-10 
timeframe being the main driver of those probabilities.

&&

.AVIATION...Scattered showers continue as a cold front continues
to move over the region. Expect predominately MVFR cigs to give 
way to a mix of high- end MVFR to low-end VFR CIGs toward 22z 
Tuesday to 00z Wednesday. Cloud cover will likely become more 
scattered this evening as skies attempt to clear out. This will 
set the stage for widespread fog and low stratus development 
tonight into Wednesday morning as high pressure builds over the 
region. Probabilities for surface visibilities below 1/2 SM 
increase to 40-70% at all inland terminals by 10-13z Wednesday. 
Fog is much less likely to occur at the coast where light offshore
winds will help prevent fog development.

KPDX AND APPROACHES...Scattered rain showers are expected to
continue into the afternoon as a cold front moves through. CIGs 
should then trend toward high- end MVFR to low- end VFR thresholds
around 23z this afternoon and attempt to scatter out this 
evening. Fog and low stratus become increasingly likely tonight 
into Wednesday morning. Probabilities for IFR conditions increase 
to around 40-60% by 12z Wednesday. Light southeast winds turn 
northwest later this afternoon. -19/DH


&&

.MARINE...A weak front will push across the waters this morning
with northwest winds increasing to around 15-20 kt. Strongest 
winds, with gusts up to 25 kt, are expected across the outer 
coastal waters north of Cape Foulweather. Winds gradually ease 
this afternoon through tonight. A long period westerly swell 
will also push into the waters, building seas to around 8 to 10 
ft. High pressure rebuilds over the waters on Wednesday as winds
turn more northerly around 10 kt or less, and seas gradually 
subside back to around 4 to 6 ft Wed night. 

A more active pattern develops later in the week as a series of 
frontal systems is expected to move across the waters beginning 
Thursday. Winds turn southerly on Thursday but are not expected to
exceed 20 kt. Expect this parade of fronts to continue through 
the weekend, with the strongest of the fronts potentially on 
Sunday. But, even then there is just a 20% chance or less of winds
reaching gale force. Seas should steadily climb towards 10 ft
through the weekend. /DH

&&

.BEACH HAZARDS...A long-period westerly swell is expected along
the northwestern Oregon and southwestern Washington coasts from
late Monday through Wednesday next week. Wave heights 
increasing to 8 to 10 ft on Tuesday may not appear to present a 
safety risk to those on area beaches, but these energetic waves 
will present a moderate to high risk for sneaker waves, waves 
which can run significantly farther up a beach than normal, 
including over rocks and jetties. In addition, a period of 
perigean spring or "king" tides means these waves will have an 
even easier time reaching high up onto beaches, limiting the 
areas which may be safe from wave action.

A Beach Hazards Statement has therefore been issued from 7 AM
Tuesday to 10 PM Wednesday. Sneaker waves can create potentially
life-threatening conditions in the surf zone when beachgoers can
be unexpectedly knocked off their feet and pulled out into cold
ocean waters. Caution should be used when in or near the water, 
and those with children should be especially watchful. Never turn
your back on the ocean, and be sure to keep an eye on the waves.
Those participating in razor clam digs should additionally
exercise caution.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory until 4 PM PST this afternoon for PZZ210.
     Small Craft Advisory until 10 PM PST this evening for PZZ271-
     272.
&&

$$

www.weather.gov/portland

Interact with us via social media:
www.facebook.com/NWSPortland
x.com/NWSPortland