406
FXUS66 KPQR 251734 AAA
AFDPQR

Area Forecast Discussion...UPDATE
National Weather Service Portland OR
1033 AM PDT Wed Jun 25 2025

Updated aviation discussion.

.SYNOPSIS...Onshore flow maintains cloudier weather and more
seasonable temperatures today through Friday. A pair of weak
disturbances will bring a chance of light rain or drizzle to
coastal areas today, spreading to inland areas north of Salem on
Thursday, however any rainfall amounts will remain minimal.
Another stretch of warm and dry weather is likely this weekend
into early next week.

&&

.UPDATE...Wednesday morning...Light drizzle is being observed over
parts of the Portland metro this morning. Manually increased PoPs
over the metro to around 15-20% to ensure there is a mention of light
drizzle in the forecast. Excluded the Hillsboro area as drizzle is
not being observed there. With low clouds in place through most of
the day today, if not the entire day, have also lowered inland high
temperatures to 65-70 degrees for elevations below 1000 feet using
the NBM 10th percentile. -TK

Note there is still a chance of light drizzle tonight and tomorrow as
well, mainly for coastal areas, southwest WA, the Portland metro and
central/northern Willamette Valley. -TK

&&

.SHORT TERM...Now through Friday Night...The upper level pattern
this morning features broad longwave troughing extending from
the Gulf of Alaska into western Canada, maintaining robust
onshore flow across the Pacific Northwest. Satellite imagery
shows an extensive marine stratus deck extending into the Coast
Range gaps and starting to spread into the interior valleys of
northwest Oregon and southwest Washington and of 3 AM Wednesday.
A weak frontal system is analyzed over the offshore waters, and
will continue to dissipate as it moves closer to the coast
today. This pattern will produce cooler and cloudier conditions
across the area today through Friday as the region remains under
the influence of onshore flow and upper level troughing. As
such, expect temperatures much closer to or even slightly below
seasonal norms in the low to mid 70s across the interior
valleys this afternoon, with coastal locations remaining in the
low to mid 60s. The decaying frontal boundary approaching the
coast along with a weak embedded upper level disturbance will
keep a chance of light rain or drizzle over coastal areas this
morning, with chances mainly confined to locations north of
Tillamook by this afternoon. Models continue to depict little if
any QPF accompanying this system, keeping rainfall amounts
capped at a trace to a few hundredths of an inch along the
coast through this evening. Expect inland locations to remain
dry today.

A second weak system will arrive tonight into Thursday morning,
bringing another chance of light rain to coastal areas and also
inland areas north of Salem. Model QPF is once again minimal,
resulting in a trace to a few hundredths at best in most
locations as the NBM depicts only a 15-20% chance to even
receive a tenth of an inch of precipitation at Astoria and
along the south Washington coast through Thursday evening.
Friday then looks to be drier, but temperatures will remain
about the same in the low to mid 70s inland and the 60s along
the coast as benign onshore flow persists over the region. /CB

.LONG TERM...Saturday through Tuesday...Saturday will bring the
beginning of another warming trend as high pressure begins to
build over the western CONUS. Expect inland highs to jump up
into the low 80s on Saturday as a result. Temperatures maintain
an upward trajectory as the ridge amplifies Sunday into Monday,
with probabilities to exceed 90 degrees inching upward in the
interior valleys with recent model runs. The NBM now depicts a
30-50% chance to reach 90 degrees through most of the Willamette
Valley on Sunday, with those probs rising to 60-80% on Monday.
The mid 90s appear to be a reasonable higher end outcome on
Monday as probs to reach 100 degrees reside are only 1-3% in the
Willamette Valley at this time. It does not appear that coastal
areas will join in the warming trend as low level onshore flow
continues to moderate temperatures in the mid to upper 60s to
perhaps around 70 degrees away from the immediate coast.
Although the heat looks to peak on Monday across the area,
models hint at warm and dry weather continuing into next week
with temperatures remaining in the 80s for Tuesday and beyond.
/CB

&&

.AVIATION...Widespread MVFR conditions due to a deep marine cloud
deck. Recent reports have shown this marine layer to be around 2000
ft deep. With the cooler air, some drizzle is being reported through
the area which may reduce VIS at times. Given the depth of the
clouds, will struggle to lift to VFR today. Within the Willamette
Valley terminals is where the highest probability of low-end VFR
conditions are possible. Have included a lower deck here but cannot
rule out a lack of improvement.

Overnight conditions will degrade once more.


PDX AND APPROACHES...MVFR becoming lower end VFR in the afternoon
after 21Z. Low confidence in the presence of VFR conditions due to
the depth of the marine layer. Winds will remain WNW becoming light
and northerly overnight. -Muessle

&&

.MARINE...A series of weak frontal passages through Friday will
bring about west to southwest winds across all waters. Minimal
impacts expected as sustained winds are forecast between 5-10 kt
through early Friday. High pressure returns Friday afternoon
bringing a return of west to northerly winds across all waters.
By Saturday, high pressure looks to be well established and will
result in breezy northerly winds. Guidance suggests a
60-80% chance of northerly wind gusts up to 30 kt by late
Saturday/early Sunday. Will continue to monitor and issue a
Small Craft Advisory if warranted. Expect general seas of 3-5 ft
with a slow build towards 4-6 ft by late Saturday/early Sunday.

A Small Craft Advisory has been issued through 0800 Wednesday
for the Columbia River Bar due to a very strong ebb current
bringing seas up to 7 ft. /42

&&

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

&&

$$

www.weather.gov/portland

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