Gresham, Oregon 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

467
FXUS66 KPQR 180556
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
956 PM PST Fri Jan 17 2025

.UPDATED AVIATION DISCUSSION...

.SYNOPSIS...High pressure is expected to remain in place into
next week, maintaining cool temps and dry conditions. Expect
highs in the upper 30s to low 40s and low in the upper 20s to
low 30s for inland valley locations into early next week.

&&

.DISCUSSION...Tonight through Friday...Water vapor satellite imagery
reveals a high amplitude shortwave ridge over the far northeast
Pacific with a shortwave trough dropping southeastward across the
Inland Northwest and northern Rocky Mountain states. This has placed
the Pacific Northwest under large scale north to northwesterly flow
aloft. Increasing low level north to northeasterly flow will lead to
drier air spreading into the region. This will lead to a reduction in
fog and low clouds and more widespread below freezing temperatures
beginning this weekend and continuing into early next week.

Easterly winds will keep temperatures from dropping quite so low near
the mouth of the Columbia River Gorge. In addition, north to
northeasterly winds in the Willamette Valley will keep temperatures
from falling too quickly each evening. However, locations that do
eventually see the surface decouple from the breezier conditions will
see temperatures plummet into the 20s. At this point, there remains a
10% chance or less for the inner Portland/Vancouver to drop into the
mid-20s. However, those probabilities remain considerably higher
(generally between 50-80%) for outlying areas and most of the lower
elevations of northwest Oregon and southwest Washington for Saturday
night through Monday night. Cold Weather Advisories appear
increasingly likely to be needed for this timeframe for the Cascade
foothill valleys, the lower Columbia River Valley, northern Clark
County, the Tualatin Valley, the rest of the Willamette Valley south
of the Portland metro and the Coast Range valleys.

Later next week, there is a 10-15% chance that the ridge will weaken
and increasing zonal flow will lead to a slight chance for light
precipitation Wednesday for primarily southwest Washington. While
snow levels appear most likely to be well above the valley floor
there is a 10% chance that snow levels start off initially near sea
level before quickly rising so even the worst case scenario produces
few impacts.

Ensemble guidance continues to reveal quite a bit of uncertainty
regarding the large scale weather pattern at the end of the week.
Nonetheless, confidence is increasing that at least some light
precipitation will spread into the region next Friday. The
probability of it coming in as valley snow appears to be less than
5% at this point.


&&

.AVIATION...We`ll continue to see high pressure preside over the
region through the TAF period. Satellite and surface observations
show low stratus has built back across the inland valleys late
this evening after a brief period of partial clearing Salem
northward with most sites experiencing MVFR to IFR CIGs/VIS as of
05-06z. Expect largely persistent conditions the rest of the
night into Saturday morning. However, compared to the past few
days offshore flow is expected to increase as Saturday progress
which bodes well for at least the Portland Metro returning to VFR
conditions by Saturday afternoon(after 18-20z) due to the
development of east winds through the Columbia Gorge. It`s likely
KUAO and KSLE see some improvement as well but confidence is much
lower regarding the exact timing - MVFR CIGs hold through the
period at KEUG. For coastal sites VFR conditions are expected to
continue outside of localized pockets of fog around sunrise.

PDX AND APPROACHES...MVFR CIGs continue tonight with the potential
for a period of IFR CIGs right around sunrise (~30%). As easterly
winds increase through the Gorge Saturday morning, clouds should
be quicker to clear than this past afternoon (Friday) with VFR
conditions returning roughly ~17-20z. Confidence in the exact
timing is only moderate. High confidence by 22-00z mostly clear
skies will prevail with easterly winds 5-10 knots. -Schuldt

&&

.MARINE...Offshore winds generally below 15-20 kt today and
into tomorrow. Winds will become more northeasterly as a thermal
trough returns to the Oregon coast and persists through the
weekend and into early next week. Seas likely hover around 6 to
9 ft today and through the weekend. A long period swell is
expected to push into the coastal waters on Saturday with a
period of around 20 seconds, with seas likely remaining around 7
to 8 ft through Sunday. Relatively quiet weather continues into
early next week. ~Hall

&&

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

$$

www.weather.gov/portland

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