532
FXUS66 KPQR 241049
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
249 AM PST Fri Jan 24 2025

.SYNOPSIS...High pressure rebuilds after a weak front passed
through today. This high pressure will persist through next
week until another disturbance arrives. Confidence is low in the
long term precipitation forecast.

&&

.SHORT TERM...Now through Sunday Night...This evening a weak
front passed over the area bringing minimal light precipitation.
The front moved in earlier and faster than previously expected.
The real impact, if you can really even call it that, is the
widespread cloud cover it brought in. These clouds have left
temperatures warmer than just about every night for the last
week. Observations show more rural areas below freezing, while
those in urban areas sit above freezing. These could be due to
the heat island effect, or the fact that there is more stratus
to the north. Satellite does show more cloud cover which
insulates the land and limits radiational cooling. Overall
though, a warmer night.

Through the day, clouds will clear as high pressure rebuilds.
Will see another round of cold overnight temperatures as colder
air digs down from the north. Based on the upper air pattern, a
negatively tilted trough at 500 mb will push southward and usher
in cold air to the Columbia Basin by the evening. This trough
passage will cause the pressure gradient to intensify and
easterly winds to increase. The easterly winds will usher in
this colder air. The concern here is the combination of colder
air and windier conditions. Apparent temperatures will drop with
rural areas and the southern Willamette Valley seeing values in
the upper teens. Up north near the Columbia, temperatures will
be more moderated and winds slightly higher. Temperatures will
be warmer here. Have not issued a Cold Weather Advisory at this
point as there is still some concern with how long the stratus
will stay in place. If the clouds linger through the early
evening it will inhibit cooling and thus keep ambient
temperatures warmer.

A similar trend in place on Sunday but with an even cooler
airmass in the Columbia Basin. At 850 mb, temperatures are
around -8 deg C Sunday morning. The coldest temperatures of the
weekend will occur Sunday. -Muessle



.LONG TERM...Monday through Thursday...Offshore flow persists
but the cold air pool will shift southward on Monday. Overnight
temperatures will steadily warm through Wednesday but will not
be near normal by any means. Will continue to see below normal
low temperatures through the week. By Wednesday, the pattern
becomes convoluted as long-range models struggle to align.
Looking at the 500 mb ensemble heights, there is an overall
trend of a ridge over us and a digging low over the desert
southwest. The intensity of the ridge is the piece of the puzzle
with the most questions. The ECMWF is putting the ridge axis
nearly directly over the state of Oregon, while the Canadian is
flatter and more westerly. This difference is even better
observed in the Thursday synoptic pattern. There are a number of
different outcomes with the ECMWF trending cooler and wetter,
and the GFS drier. This is an important component to remember
as this system will be entering into a cold airmass.

At this point, not going to hang my hat on winter weather, but
there is a non-zero possibility of low elevation snow in
Washington. Ultimately it will come down to how strong the ridge
is and the strength of the incoming low pressure. If the low
outweighs the high, then winter weather isn`t out of the
question. However, we have yet to see the "sacrificial lamb"
which is a system that helps to eat away at the ridge. In these
types of patterns with a very stable and anchored pattern, you
need a little "oomph" to overcome it. Will continue to watch it
but my confidence is quite low. -Muessle


&&

.AVIATION...Early this morning a weak frontal boundary has
resulted in lowering cigs across the region with a mix of VFR to
MVFR CIGs - locally lower north Oregon coast near KAST. These CIGs
likely creep a touch lower headed into sunrise (~15-16z) before
rising headed back into the late morning and midday hours. High
confidence in prevailing VFR conditions returning this afternoon
through the evening. Winds generally remain less than 5-10 knots
at all sites through the TAF period.

PDX AND APPROACHES...CIGs have deteriorated to a mix of MVFR to
VFR this morning with periods of MVFR CIGs possible through ~16z
before prevailing VFR conditions return. Light and variable winds
around 5-8 knots or less will continue as well. -Schuldt

&&

.MARINE...A weak upper-level disturbance passing overhead will
exit the region this morning followed by high pressure quickly
rebuilding across the Pacific Northwest; overall rather benign
conditions expected moving forward given the time of year. We`ll
likely see the marginal Small Craft level wind gusts continue over
portions of the waters (mainly outer waters Cape Falcon Southward)
through today into Saturday/Saturday evening with N-NNE gusts up
to 21-27 kt at times. While Small Craft conditions are ongoing,
seas will build to 5-9 ft at 12-15 seconds today before easing
back into the 4-7 ft range this weekend into early next week.
N-NNE winds will eventually decrease as well with high confidence
in below Small Craft Advisory level winds (<21-22 knots) across
the waters by Sunday afternoon lasting through Tuesday night.
Later Wednesday towards the end of next week we`ll need to keep an
eye on the reemergence of a more active weather pattern, however,
the exact details and impacts have yet to be ironed out. -Schuldt

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory until 4 AM PST early this morning for
     PZZ252-253.
     Small Craft Advisory until 4 PM PST this afternoon for PZZ271.
     Small Craft Advisory until 4 PM PST Saturday for PZZ272-273.
&&

$$

www.weather.gov/portland

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