356
FXUS66 KPQR 170358
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
858 PM PDT Mon Jun 16 2025

.SYNOPSIS...Onshore flow will maintain seasonable temperatures
through much of the coming week. Chances for light rain return
to the coast Monday night into Tuesday and inland Tuesday night
into Wednesday, with very little to no measurable rain expected
for most inland locations. Transitioning to a cool and showery
weather pattern Friday into Saturday as a closed upper level low
settles over the region and brings more substantial rain
amounts to the area.

&&

.SHORT TERM...Now through Tuesday Night...Weak onshore flow
through the next few days with a few shortwave troughs moving
within the flow. Tonight the first shortwave will arrive which
will bring a slight chance (15-30% chance) of rain - especially
along the coast. Forecast simulated reflectivity shows very
showery conditions so some areas may receive accumulating
precipitation while others will be rain free. Accumulation will
be minimal, though higher terrain along the coast will see the
most with up to 0.2 inch possible. Due to a slight rain shadow
effect, inland areas will stay drier.

Seasonable temperatures and partly cloudy skies. With westerly
flow through the column, there will be minimal change in the
overall forecast. Temperatures will remain in the 70s inland,
while in the upper 50s to mid-60s along the coast. Will see
highs increase by a degree or two on Tuesday, but clouds through
the day may dampen those temperatures slightly.

The second shortwave arrives on Tuesday night into Wednesday
which increases chance for rain once again. More details to
follow. -Muessle

.LONG TERM...Wednesday through Sunday...ECMWF and GFS Ensemble
guidance are both in agreement that there is potential for
shortwave- troughing on Wednesday. Following this trough, a
stronger area of low pressure brings in heavy showers Friday
through the weekend. Onshore flow will increase as pressure
gradients tighten with the introduction of troughing onshore.
Increasing winds, decreasing temperatures, and heavy showers
will increase the probability for 0.25 inch of rain or more each
day. Based on NBM ensemble guidance there is strong agreement
that the probability for 0.25" of rain or more within a 24-hour
period over the weekend is 40-50%, while the Coast, Coastal
Range, and Cascades is 65-75%. Given the showery nature of this
system, cannot rule out thunderstorms. There is currently a
15-20% chance of thunderstorms on Friday and Saturday, with the
highest probability on Friday being in the Willamette Valley,
and Saturday focuses on the Cascades. The initial shortwave
trough will only drop maximum temperatures in the Willamette
Valley about 5 degrees F, bringing temperatures from low-80s to
mid-70s. Temperatures fall even farther as the stronger low
pressure moves in. Highs along the Willamette valley will range
from near 60s degrees F in the south Valley, to the mid-70s in
the north Valley. The coast will remain "normal" in the high
50s/low 60s. -Ruhl/Muessle

&&

.AVIATION...Currently VFR conditions under clear skies across the
airspace. These conditions are expected to persist for the
majority of inland locations through the TAF period. However,
could see some IFR/LIFR conditions with a 5-15% probability
develop near KEUG and KSLE starting around 12Z Tuesday. For
coastal terminals, CIGs will likely deteriorate towards
MVFR/IFR/LIFR around 09Z-11Z Tuesday with probabilities around
25-60%, highest north of KTMK to KAST and lowest south of KTMK
towards KONP. Expect west to northwesterly winds around 5-10 kt
this evening, becoming light and variable around 06Z Tuesday.
Any lowered flight conditions should improve towards VFR around
16Z-18Z Tuesday along with winds becoming west to south around
5-10 kt. Also, a weak frontal passage staring around 18Z Tuesday
will bring light precipitation to the coast, precipitation will
also likely start to impact northern, Willamette Valley
locations around 03Z-06Z Wednesday.

*KTTD ASOS is currently INOP except for altimeter and will be AMD
 NOT SKED.

PDX AND APPROACHES...VFR conditions under mostly clear skies
persist through the TAF period. Northwest winds around 5-10 kt,
becoming light and variable around 06Z-09Z Tuesday. Around
16Z-18Z Tuesday winds becoming westerly around 5-10 kt. Light
precipitation will also likely start to impact northern,
Willamette Valley locations around 03Z-06Z Wednesday. /42

&&

.MARINE...A weak disturbance is expected to cross the region this
evening, supporting a wind shift from northwesterly flow to
southerly flow late this evening and through Tuesday. A westerly
swell is also expected to move into the waters this evening,
increasing seas from around 3 feet to around 6 ft at 10 seconds.
Combined seas still look to remain 7 ft or less through the week.
Winds remain southerly through Tuesday, gradually turning back to
the west/northwest on Wednesday. Another disturbance arrives
Monday, bringing mostly westerly winds through the weekend.
~Hall/Batz

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...None.

&&

$$

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