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.
&&

$$

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