220
FXUS66 KPQR 262309
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
309 PM PST Tue Nov 26 2024

.SYNOPSIS...A prolonged period of calmer and drier conditions
will shortly be upon us just in time for Thanksgiving. Expect
high pressure to gradually build across the region on Wednesday
lasting through the weekend. Thus impacts will primarily revolve
around area of overnight/morning fog and cooler low
temperatures.

&&

.SHORT TERM..Tonight through Thursday...The pesky area of low
pressure which had been sitting off the coast the last several
days has finally transitioned into an open wave trough and
pushed inland through southern Oregon today. As this
disturbance continues to drift further eastward and heights
begin to build aloft well see showers come to an end in the
inland valleys tonight. With a little bit of clearing, lighter
winds, and ample surface moisture patchy fog will once again be
prevalent headed into Wednesday morning. Upper flow will
gradually turn more northwesterly through the rest of Wednesday
so not much in way of shower potential for the region, though
can not completely rule out a stray showers along the coast and
over the Cascades. Thursday appears very similar with not much
change - cooler and dry with morning fog/low clouds.

.LONG TERM...Friday through Monday...Fortunately, if you enjoy
drier, cooler, and calmer weather youre in luck late week and
this weekend. Both deterministic and ensemble guidance show a
ridge to high pressure slowly building overhead with dry
conditions for the inland valleys and mostly dry weather for the
coast, coast range, and Cascades. Theres still a small subset
of ensemble members(20-30%) and that depict a chance of light showers
across far northwest Oregon and over the south Washington
Cascades on Friday due to a weak upper-level shortwave
circumventing the northeastern periphery of the ridge. Still,
the other 70-80% of ensemble models have a strong enough ridge
in place to shunt this weak upper-level system further north
leaving the region completely dry. Otherwise nearly all
ensembles show the ridge amplifying further with the ridge axis
centering over the coastline this weekend into Monday. This
setup is conducive for morning fog/low clouds across the
Willamette valley and other protected inland valleys followed by
some afternoon clearing; rinse and repeat each day as long as
we`re under the influence of the ridge. It`s worth noting the
NBM shows a 65-90% chance for low temperatures to drop below
freezing for most of the inland Valleys Friday morning through
Monday - closer to 30-40% urban Portland/Vancouver metro. Keep
this in mind when making travel plans as freezing fog can be
adverse to roadway conditions. Guidance starts to hint at the
breakdown or at least the easterly progression of the high
pressure ridge come Tuesday into the middle of next week,
however, significant uncertainty exists as to exactly how/when
any noticeable pattern change will occur.
-Schuldt/Rockey

&&

.AVIATION...Currently, widespread MVFR and IFR conditions across
the airspace. Tonight, a weak disturbance will bring northwest
flow aloft across the area. This should bring areas of MVFR
conditions (55%-70% probability) across the airspace starting
around 03Z-06Z Wednesday with around a 35%-45% probability for
IFR/LIFR conditions for inland locations starting around 10Z-12Z
Wednesday.

PDX APPROACHES...MVFR conditions will gradually improve towards a
mixture of MVFR/VFR, but cigs may struggle to get above FL040 for
visual approaches as next system arrives tonight. This system will
bring another round of MVFR and IFR conditions starting around
10Z-12Z Wednesday. /42

&&

.MARINE...Benign weather through the weekend and into the start of
next week as high pressure builds over the waters. Expect
northerly winds with seas expected 4 to 6 ft with a slow build
towards 8 ft on Sunday. /42

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&

$$

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