Lebanon, Oregon 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

397
FXUS66 KPQR 272129
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
152 PM PDT Tue May 27 2025

.SYNOPSIS...Sunny skies and warm temperatures expected through
Wednesday as high pressure builds over the Pacific Northwest.
An approaching system will lead to a 15-20% chance for
thunderstorms along the crest of the Cascades Wednesday
afternoon. The main cold front moves in late Wednesday night
into Thursday, returning clouds, rain showers, and cooler
temperatures. Warmer and drier conditions return Friday to
Saturday before another system arrives by early next week.

&&

.SHORT TERM...Now through Thursday night...Sunny skies prevail
across northwest Oregon and southwest Washington this afternoon
as ridge of high pressure builds over the Pacific Northwest.
Expect high temperatures to top out in the low 80s this
afternoon across the Willamette Valley, southwest Washington
lowlands, Columbia River Gorge, lower Cascade valleys, and Upper
Hood River Valley. Meanwhile, the coast remains more mild with
highs in the upper 60s to low 70s. The air is drier today,
thanks to a weak offshore pressure gradient leading to light
northerly to northeasterly winds. Meanwhile, light easterly
winds prevail through the Columbia River Gorge as observed KTTD-
KDLS pressure gradients have been around -2.5 mb today. Expect
the gradient through the Gorge to peak around -3 to -4 mb
tonight, which isn`t too strong but will lead to wind gusts of
25-35 mph particularly for exposed ridges of the Gorge (Three
Corner Rock/Corbett).

Wednesday is looking to be the warmest day of the year so far
for some interior valley locations as the upper level ridge
amplifies over the western United States. The caveat is that
this ridge will gradually move eastward throughout the day,
along with a return of onshore flow ahead of an incoming system.
This will actually keep temperatures moderated along the coast
and across the central and southern Willamette Valley as
west-southwesterly winds return. The warmest locations are
expected across the Portland/Vancouver Metro, southwest
Washington lowlands, Columbia River Gorge, and Upper Hood River
Valley, where highs are forecast in the mid to upper 80s.
Meanwhile, onshore flow seeping into the central and southern
Willamette Valley will keep temps topped out in the upper 70s
to low 80s from Aurora to Eugene, with 60s along the coast.
Probabilities for exceeding 90 degrees has fallen to 5-15% for
the Portland/Vancouver Metro, and less than 5% for the rest of
the Willamette Valley.

By late Wednesday afternoon and evening, attention shifts to an
upper level trough approaching the Pacific Northwest. Prior to
the arrival of the main cold front, this system will bring a
15-20% chance for thunderstorms and showers along the crest of
the Cascades. This approaching trough will bring south-southwest
flow aloft along with more 850-700 mb moisture. Combined with
increasing instability Wednesday afternoon due to daytime
heating (HREF shows SBCAPE values exceeding 1000 J/kg from the
crest of the Cascades and into central Oregon) and local terrain
forcing, this will aid in convective activity. High resolution
models are showing showers and isolated thunderstorms popping up
around the Cascade crests around 4-6 PM and lasting as late as
8-11 PM. The westerly component of winds aloft should keep any
pop-up showers and thunderstorms east of the Cascades.

Late Wednesday night into Thursday morning, the main cold front
associated with the upper level trough arrives and bring more
widespread cloud cover and light rain showers. Rain arrives
along the coast some time between 11 PM to 2 AM Thursday, and
spreads inland by 2 to 5 AM Thursday. Amounts are pretty light;
around 0.10-0.20" along the Coast and Coast Range, and a trace
to 0.05" for interior locations east of the Coast Range. NBM
guidance suggests a 20-40% chance of exceeding 0.25" of rain
along the coast from Lincoln City northward, and 5-15% south of
Lincoln City to Florence. Expect daytime temperatures on
Thursday to be much cooler than Wednesday due to the increased
cloud cover, with highs forecast in the low 70s across the
Willamette Valley.          -Alviz

&&

.LONG TERM...Friday through Tuesday...At the start of the long
term period, deterministic and ensemble guidance are in good
agreement on the arrival of another transitory ridge of high
pressure leading to warming temperatures Friday - highs rise
back into the low to mid 80s. However, confidence in the
forecast decreases going into Saturday as model spread
increases and guidance struggles to agree on the degree of
ridging amplification east of the Cascade crest as well as the
eastward progression of a trough over the northeast Pacific.
The NBM 10th-90th percentile for high temps highlights the
degree of uncertainty well on Saturday afternoon, suggesting
highs could range anywhere from the mid 70s to low 90s. For now,
the Saturday high temperature forecast remains in the middle of
that spread - low 80s. There is somewhat better agreement in
the arrival of a trough feature and potential cut-off low by
Sunday into early next week with increasing shower chances and
daytime highs remaining in the 70s.       -Alviz/Schuldt


&&

.AVIATION...Few concerns as conditions remain clear sky VFR
throughout the majority of the period for most areas. The exception
will be some the southern coast, which sees some low clouds begin
moving in around 12z Wed ahead of the next band of moisture. Around
a 60-70% chance of MVFR ceilings or lower at that time at southern
coastal terminals such as KONP. For northern coastal terminals,
closer to a 10-20% chance of MVFR cigs or below at that time. For
all other terminals, clear sky VFR throughout the period, with
generally northerly winds. Gusts up to 15-20 kts possible at all
terminals Tuesday afternoon. Winds decrease going into Tuesday
evening.

PDX AND APPROACHES...Clear skies VFR conditions throughout the
period. Northerly winds gusting to 10-15 kts Tuesday afternoon,
weakening greatly going into Tuesday evening. /JLiu

&&

.MARINE...Thermally induced surface trough continues building up
at the Oregon coast this afternoon and evening, and a Small Craft
Advisory is in place for the southern waters owing to gusts up to 20-
25 kts at times through the rest of Tuesday afternoon and evening.

Additionally, a Small Craft Advisory remains on track for the
Columbia River Bar on Wednesday morning due to a very strong ebb
current that could create seas up to 8 ft with steep ebb chop
possible.

Going forward, winds turn southerly on Wednesday as the next front
begins to push in, with rain beginning Wednesday night. Wednesday
night and Thursday morning look to see a 20-40% chance of reaching
Small Craft Advisory level winds again at that time. From Thursday
morning onwards, northerly winds under 15 kts with a westerly swell
around 5-7 ft through the workweek. /JLiu

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 4 AM to 8 AM PDT Wednesday for PZZ210.

     Small Craft Advisory until 11 PM PDT this evening for PZZ253-
273.

&&

$$

www.weather.gov/portland

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