130
FXUS66 KPQR 070403 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
903 PM PDT Tue May 6 2025

Updated Aviation Discussion...

.SYNOPSIS...Warm and sunny this afternoon as high pressure
remains overhead. A weak system will bring cooler and cloudier
weather for Wednesday, possibly accompanied by very light rain
Wednesday afternoon and evening. Benign conditions persist into
the weekend as temperatures rebound into the upper 70s for
Friday and Saturday. Cooler and potentially wetter weather looks
to return Sunday into next week.

&&

.SHORT TERM...Now through Thursday Night...Mostly sunny skies
prevail across the are this afternoon as a narrow ridge of high
pressure remains over the region, allowing temperatures to climb
into the low 80s in many locations in the interior valleys. Weak
offshore flow has allowed coastal areas to warm into the low 70s
in some locations. Visible satellite shows a few high cirrus
clouds starting to move into the area ahead of the next system
as the ridge axis begins to shift east of the Cascades.

This system will arrive on Wednesday as a shortwave trough moves
across the Washington Coast and into southern British Columbia
by Wednesday evening, dragging a weak surface cold front across
western Oregon during the afternoon. Expect high temperatures
on Wednesday to run 10-15 degrees cooler than today as a result,
with highs in the interior valleys closer to 70 and coastal
areas back down in the upper 50s. The front will bring drizzly
conditions to the coast and a chance for some light rain inland,
but rainfall amounts continue to look minimal. The latest NBM
guidance is advertising a 40% chance for any measurable
rainfall in the Portland area through Wednesday night and
closer to a 20% chance farther south towards Eugene, but the
probability of getting a tenth of an inch is 10% or less for the
Willamette Valley and only 15-20% even along the coast.

Expect benign onshore flow on Thursday as any precipitation
departs the area in the wake of the trough, yielding pleasant,
seasonable conditions with high temperatures again around 70
degrees. /CB


.LONG TERM...Friday through Tuesday...Friday and Saturday will
bring another warming trend as 500 mb heights rise on the
periphery of a stout upper level ridge building over the
western CONUS. Currently expect highs in the mid to upper 70s
for the interior valleys both days, with NBM giving the Portland
area around a 50% chance to reach 80 degrees on Friday and a
40% chance on Saturday. Coastal areas are likely to remain
cooler during this period as low level onshore flow persists
over the area. There is increasing confidence in a return to
cooler and wetter weather from Sunday into the early part of
next week, the details of which remain in flux as all WPC
ensemble clusters depict some version of upper level troughing
over the region but with notable differences in position and
magnitude. The long term forecast thus reflects a middle ground
NBM-heavy approach with temperatures slightly below seasonal
normals and broad brushed chances of precipitation. /CB

&&

.AVIATION...VFR conditions will persist through the TAF period
for inland terminals. As a weak front moves through the airspace
around 23Z Wednesday, expect light rain and low-end VFR conditions
to develop. Expect winds to remain rather light before 18Z
Wednesday, then increase to around 8-10 kt with gusts up to 18 kt
possible after 20-22Z Wednesday. Winds will stay westerly to
northwesterly around the Columbia River, and westerly to
southwesterly around KUAO and southward.

For coastal terminals, expect IFR conditions to begin to develop
before 09-10Z Wednesday, with increasing chances of LIFR
conditions thereafter. Guidance suggests a 30-50% chance of IFR
conditions from now until 20Z Wednesday, and a 20-40% chance of
LIFR CIGs between 09-17Z Wednesday. Conditions look to improve to
MVFR after 18-20Z Wednesday for KAST, but may remain IFR for KONP.
Conditions will heavily rely on how weak this weather system will
be when it moves through the coastal terminal airspace around
14-18Z Wednesday. Considering how weak this system looks, there is
high to moderate confidence that all coastal terminals will
improve to VFR by 20Z Wednesday. Otherwise, expect light
northwesterly winds overnight, then increasing to 8-10 kt with
gusts of 18 kt possible after 18-20Z Wednesday.

PDX AND APPROACHES...VFR through the TAF period. Light westerly
to northwesterly winds until 17Z Wednesday, then increasing to
around 8-10 kt with gusts of 18 kt possible after 22Z Wednesday.
~Hall

&&

.MARINE...High pressure will keep conditions settled. Winds are
decreasing but staying northerly. Expect northerly to
northwesterly winds around 10 kt with gusts up to 18 kt over the
next several days. Seas will be 5 to 7 ft at 12 seconds.

On Wednesday, a weak front will push over the waters. It will not
be overly impactful but could see slightly more gusty conditions,
especially in PZZ273, where gusts could reach 20 kt at times.

High pressure returns through the remainder of the week with
little change in conditions.
~Hall

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

www.weather.gov/portland

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