602 
FXUS66 KPQR 011906
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1100 AM PST Mon Dec 1 2025

.SYNOPSIS...High pressure continues over the region today with 
mostly dry conditions expected through this evening. A weak front 
will bring chances for light rain tonight into Tuesday. Dry again on 
Wednesday. Active weather returns as a series of frontal systems 
bring increasing chances for rain later Thursday through the 
weekend. Seasonable temperatures continue through the week.

&&

.SHORT TERM...Today through Wednesday night...An upper ridge of high 
pressure over the region this morning will shift east as a shortwave 
trough drops down across the Pacific NW tonight. After a chilly and 
frosty start across much of the area today, expect increasing clouds 
with afternoon temperatures only warming into the upper 40s through 
much of the lowland valleys. Temperatures likely a bit warmer along 
the coast thanks to some light offshore flow. 

A weak frontal system will push across the area later tonight into 
Tuesday. Rainfall accumulations are expected to be minimal as 
showers remain relatively shallow as a warmer air mass persists in 
the mid-levels. Most locations will only see a few hundredths of an 
inch of rain, except along the north coast, and in the higher 
terrain influenced by orographic lift, where amounts will vary up to 
a quarter inch. There is less than a 10% chance in these areas for 
amounts up to a half inch of rainfall. 

High pressure rebuilds across the region on Wednesday with dry 
weather and seasonable temperatures expected. Increasing moisture in 
the mid levels within the north to northwest flow aloft will likely 
maintain some sort of cloudiness. /DH

.LONG TERM...Thursday through Sunday...Models and their ensembles 
are in good agreement that the upper level ridge remains over the 
northeast Pacific on Thursday. But, WPC cluster analysis does 
indicate high probability of the ridge breaking down and flattening 
out, allowing for more westerly flow into the Pacific NW Friday and 
into the weekend. This should allow for frontal systems to bring 
increased rainfall and more active weather to the area. Uncertainty 
in rainfall amounts remains moderately high, but extreme rainfall 
appears very unlikely. For example, the probability for IVT values > 
250 kg/m/s from the coast to the foothills is quite high (greater 
than 80-90%) both Friday and Saturday, but the probability of IVT 
values greater than 500 kg/m/s is very low. Both the GEFS and ECMWF 
ensemble means suggest total precipitation amounts of around 2 
inches near Astoria through Sunday. The NBM suggests similar amounts 
for Friday through Sunday (72-hour period), while the 90th 
percentile (10% chance of exceeding) suggests potential for total 
rainfall amounts nearing 3 to 4 inches. Still, more beneficial with 
minimal impacts expected. Will note that HEFS guidance does show 
increasing (but still low) chances for local rivers reaching action 
or minor flood stage, with the highest chances for coastal rivers 
(up to 5-15%) into early next week. /DH

&&

.AVIATION...Low clouds that developed overnight in the southern 
Willamette Valley will slowly dissipate over the next few hours. 
There is a 10-20% chance that IFR to MVFR restrictions either do not 
retreat this afternoon or return quickly this evening to KEUG as low 
stratus tries to redevelop ahead of the next front. Speaking of, a 
weak front will drop southeastward across southwest Washington and 
northwest Oregon overnight. Little in the way of wind will accompany 
this front. This will result in a several hour window where ceilings 
will have the potential to lower into IFR and MVFR thresholds as the 
lower atmosphere saturates along the coast between 06-12z Tuesday 
and between 12-18z Tuesday for inland taf sites. Our best 
statistical model guidance suggests a 30-50% chance (highest for 
KAST and lowest farther south towards KONP) for MVFR restrictions 
developing at any given hour in the 06-12z Tuesday timeframe. 
Probabilities are more in the 30-40% range for MVFR conditions to 
develop at any given hour in the Willamette Valley, primarily in the 
12-18z Tuesday timeframe. The highest chances for IFR conditions 
will be at KAST in the 06-12z Tuesday timeframe and climb into the 
20-30% range at KEUG and KHIO in the 12-18z Tuesday timeframe and 
remain around 10% at other sites like KPDX and KSLE.
  
KPDX AND APPROACHES...VFR conditions will give way to lowering 
ceilings as a weak front slides across the late terminal late 
tonight into early Tuesday morning. Probabilities for MVFR ceilings 
start climbing between 09-12z Tuesday as the front approaches the 
region and then peak around 30-40% at any given hour between 12-18z 
Tuesday as the front crosses the region. The probability of IFR 
conditions developing at any given hour peaks around 10% between 15-
18z Tuesday. 

&&

.MARINE...With high pressure offshore today, will see north to 
northeast winds to around 10 kt, while seas remain around 4 to 6
ft. A weak front traversing the waters tonight into Tuesday will
shift winds to northwest, increasing up to 15-20 kt, while a long
period westerly swell builds seas to around 9 to 10 ft on Tuesday.
Have issued a Small Craft Advisory for the outer coastal waters
north of Cape Foulweather to cover this marginal threat.  

Winds and seas ease midweek as high pressure returns. A more
active weather pattern develops late in the week as a series of
frontal systems is expected to moves across the waters from 
Thursday into the weekend. There remains a 20-40% chance of seas
rising above 10 ft again Friday into Saturday. /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. -36

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 4 AM to 10 PM PST Tuesday for PZZ271-
     272.

&&

$$

www.weather.gov/portland

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