Johnson City, Oregon Weather Forecast Discussion

388
FXUS66 KPQR 182234
AFDPQR
Area Forecast Discussion
National Weather Service Portland OR
334 PM PDT Thu Sep 18 2025
.SYNOPSIS...Persistent onshore flow will maintain seasonable
conditions through the remainder of the week. A deeper trough
moving in from the Gulf of Alaska this weekend will bring a more
pronounced cool-down and an increasing chance for rain,
especially along the coast and across southwest Washington.
There is also a low potential for isolated thunderstorms in the
Cascades Friday through Sunday.
&&
.SHORT TERM...Now through Saturday...Tranquil conditions are expected
to prevail across the area through Saturday. A weak disturbance
continues to lift northeast while high pressure builds in from
the west. Skies remain mostly clear today through winds are
expected to be gusty through the evening as the pressure
gradient tightens. Northerly to northwesterly winds 8-15 mph
with gusts to 20 mph are possible throughout the Willamette
Valley, slightly higher along the coast with sustained winds
15-20 mph and gusts closer to 30 mph possible. Winds become
light and variable overnight. Mostly clear skies are expected
overnight for most locations as high pressure builds in from the
west. Cloud cover across the southern Willamette Valley into
eastern Lane and Linn counties will increase as a weak surface
low across northern California drifts northward tonight into
tomorrow. Lows close to average in the upper 40s along the coast
and low 50s inland are expected.
Conditions are expected to remain dry Friday with an uptick in high
temps as a short wave ridge moves overhead. Highs in the low to mid
80s are expected inland and 60s along the coast. Northerly winds
will return as surface high pressure remains in place. An area of
moisture associated with the northern California low moving
northward will come into central OR. Confidence remains low,
around 10% or less, for a shower or stray storm to develop
across far eastern Lane and Linn counties tomorrow afternoon and
evening. Saturday will remain dry with highs around average.
Winds turn westerly, then southwesterly late in the day as a
cold front approaches the area. -Batz
.LONG TERM...Saturday night through Wednesday...Rain chances
increase this weekend as a strong shortwave trough digs
southeast from the Gulf of Alaska. A cold front associated with
this system will approach late Saturday into Sunday, bringing
probabilities of measurable precipitation to 30-60% across most
of northwest Oregon and southwest Washington. Lower
probabilities (as low as 10-25%) are favored for the southern
Willamette Valley and the Lane/Linn County Cascades and
foothills. The highest chances, in the 50-80% range, are
expected north and west of a line from Willapa Hills to
Tillamook, including the southwest Washington coast and Astoria.
Temperatures will trend cooler under cloud cover and frontal
passage, with highs Sunday in the low 70s inland and 60s along
the coast. Heading into early next week, conditions remain
seasonable with inland highs in the mid to upper 70s and coastal
highs in the 60s. Guidance suggests another round of
precipitation Tuesday into Wednesday as low pressure off
northern California lifts northward into a broader trough over
the northeast Pacific. Probabilities of measurable precipitation
at this time are around 20-30%, but timing and coverage remain
uncertain. ~Hall/Batz
&&
.AVIATION...Satellite imagery and terminal observations as of late
Thursday morning show MVFR stratus east of I-5 in the Willamette
Valley and stratus breaking out along the coast. By 19-20z Thu,
expect stratus to completely burn off across the area. VFR
conditions will then prevail as high pressure maintains mostly sunny
skies today. Some high clouds will move in from the south later this
afternoon. Northerly to northwesterly winds will be breezy this
afternoon with gusts to 20-25 kt at any given terminal. VFR
conditions continue overnight under mostly clear skies, with a 20-
30% chance for IFR/MVFR CIGs along the coast after 12z Fri as the
lower atmosphere moistens.
KPDX AND APPROACHES...Low stratus should burn off by around 19z Thu.
VFR conditions then prevail throughout the TAF period with clear
skies. Northwesterly winds 5-10 kt with gusts up to 20 kt this
afternoon. Winds weaken overnight.       -Alviz
&&
.MARINE...
Gusty northerly winds continue across coastal waters
through this evening as high pressure offshore persists along with
strengthening thermal low pressure extending from northern
California into the southern Oregon coast. Expect wind gusts up
to 25-30 kt, peaking later this afternoon and evening. Buoy
observations early this morning show wave heights around 9-11 ft
with a dominant period of around 12 seconds. Expect choppy seas to
persist through tonight, as winds gradually ease by early Friday
morning. Small Craft Advisories remain in effect across all
coastal waters, including the Columbia River Bar, through this
evening. Have extended the advisory through the rest of tonight as
well for the outer waters.
High pressure shifts south on Friday as pressure gradients weaken
across the coastal waters. Northerly winds remain breezy, but
expect gusts to generally remain below 20 kt, though there is
still around a 30% chance of SCA wind gusts up to 25 kt across
the southern marine zones. A frontal system arrives this weekend
from the north, returning southerly winds later Saturday. No
substantial impacts expected for now, with guidance suggesting
around a 20% chance for southerly wind gusts up to 25 kt. /DH
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory until 11 PM PDT this evening for PZZ210.
     Small Craft Advisory until 5 AM PDT Friday for PZZ251>253-
     271>273.
&&
$$
www.weather.gov/portland
Interact with us via social media:
www.facebook.com/NWSPortland
x.com/NWSPortland

NWS PQR Office Area Forecast Discussion