941
FXUS66 KPQR 040452
AFDPQR

Area Forecast Discussion...Updated Aviation
National Weather Service Portland OR
951 PM PDT Thu Jul 3 2025

.SYNOPSIS...Onshore flow continues as a series of short wave,
upper level troughs move over the area tonight through Friday.
This will increase mixing and bring some moist air into the
region. As a result of this pattern there is a slight chance
(15-20%) of rain showers late tonight through Friday afternoon
along the Cascades. Could see isolated thunderstorms over the
ridges through the same time period. Warming and drying trends
return for the weekend and persist through at least the middle
of the upcoming week.

&&

.SHORT TERM...Tonight through Friday Night...Onshore flow
remains in place as a series of upper level, shortwave troughs
moves through the region over the next 24 hours. This will bring
about seasonal temperatures in the 60s for the coast, upper 70s
to low 80s for inland locations and upper 60s to low 70s for
the Cascades. In addition to the moderate temperatures, an
influx of moist air will also be introduced into the region.
This elevated moisture will result in an uptick in general
instability as mixing increase. CAM soundings show somewhat
favorable south/southwest flow as well as CAPE values around
600-1000 J/kg. While CIN values are between 20-60 J/kg, there
are enough signals within the models, as well as via pattern
recognition to warrant a slight chance (15%-20% probability) of
thunderstorms for the Lane and Linn County Cascades starting
tonight through Friday afternoon.

Otherwise, Friday looks to be very similar to today for the
majority of our CWA. The only differences look to be that
daytime highs will be a few degrees cooler and more widespread,
marine stratus across the region. Also, expect elevated,
westerly winds through the Columbia River Gorge through Friday
night. /42


.LONG TERM...Saturday through Wednesday... For the start of the
weekend, warmer and drier conditions return. The upper level
pattern starts to shift into a Rex like, blocking pattern.
The cut-off low of this rex-like pattern looks to hover just off
the northern coast of California and a more zonal-ish flow
pattern for OR and WA. With this pattern over the Pacific, a
surface low over the Great Basin will enable warm and dry air to
re-enter the region. As a result, longer range models have 850
mb temperatures warming towards 18C to 20C, which will bring
daytime highs into the upper 80s to low 90s for the weekend and
continue to warm through Wednesday. At this time, the warmest
days looks to be Monday and Tuesday. As Wednesday approaches,
the aforementioned low looks to be pulled northward. This will
bring about a slight cooling trend for the middle of the week.
/42

&&

.AVIATION...Generally clear with VFR conditions in place for all
terminals, though some intermittent MVFR marine clouds may be
possible at coastal terminals before 10z Fri. Around 10z Fri, some
marine clouds are expected to develop at coastal terminals with
70-90% confidence. MVFR conditions will develop at these
terminals, with a 40-50% chance of IFR conditions at that time as
well. Lowered ceilings at the coast continue through the TAF
period, though some improvement is possibe late Friday morning.

Inland, just VFR conditions are expected, though there is a 20-30%
chance at some of the northern Willamette Valley terminals of MVFR
stratus developing briefly near the end of Thursday night around
15z Fri. Winds will drop below 6-8 kts at all terminals, but
diurnal winds will cause an increase yet again starting around
16-20z Fri at all terminals, with north-northwest winds with gusts
up to 20-25 kts possible.

PDX AND APPROACHES...VFR conditions throughout the period. Winds
NNW under 6 kts, though diurnal winds cause an increase back up to
20 kt gusts beginning around 18z Fri. 20-30% chance of MVFR marine
stratus developing for a few hours, between 15-19z Fri. /JLiu

&&

.MARINE...Persistent surface high pressure offshore will result in
continued northerly to northwesterly winds across the waters.
Diurnal gusts will reach 10-15 kt north of Cape Falcon and 15-20
kt from Cape Falcon to Florence each afternoon, easing to around
10 kt overnight. Seas will continue at 3-6 ft through the
weekend, before strengthening surface high pressure sees winds and
seas build Sunday into next week. -Picard/JLiu

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

www.weather.gov/portland

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