612
FXUS66 KPQR 040902
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
202 AM PDT Fri Jul 4 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...Now through Monday...The previously advertised
shortwave upper level troughs are moving over the area with the
first one exiting the forecast area this morning. The second
shortwave will pass over eastern Oregon later this morning.
High resolution simulated reflectivity shows the next batch of
showers arriving right around sunrise then exiting in the
afternoon. Showers will remain right over the Cascades. There
continues to be a slight chance (less than 20%) for
thunderstorms over the highest elevations of the Willamette Natl
Forest late this afternoon as the moisture meets peak daytime
heating. Any thunder storms would be far and few between.

Temperatures will be similar to Thursday with highs in the 70s
throughout much of the area, and in the lower 60s along the
coast. Skies will be mostly cloudy to the north and clear in the
south.

Saturday through Sunday will encounter a gradual warm up as high
pressure builds, and a low aloft forms over northern
California. This low has shifted further south than previous
model runs which will reduce the intensity of the ridging
pattern overall. Winds aloft will start to become north to
northwesterly through the weekend. -Muessle


.LONG TERM...Monday through Thursday...The upper level low will
push inland over northern California on Monday which will
enhance the developing ridge. There continues to be some
disagreement in global models on where this low will park. If
the deterministic GFS rings true, high temperatures on Monday-
Wednesday will be cooler than if the deterministic ECMWF
manifests. These scenarios can easily be observed in the 850 mb
temperatures on Monday and Tuesday where they range from 16-20
deg C. Because of this, there remains a bit of uncertainty in
the temperature forecast. Lets dive into the numbers of some of
the warmest areas:

On Monday, the 25th-75th percentile (most likely range) high
temperatures range from 88-92 deg F in the Willamette Valley and
a similar spread in the Upper Hood River Valley. The southern
Willamette Valley around Eugene and Cottage Grove are trending
warmer due to more of a northeasterly flow. On Tuesday, the
25th-75th percentile max temperatures range from 90-95 deg F in
the Willamette Valley, and 91-98 deg F in Hood River. The coast
will see very little variation each day. Overall, the spread
isn`t too far to recognize that Monday and Tuesday will be hot
with a Moderate HeatRisk for many areas. For those susceptible
to heat, take precautions.

Transitioning into Wednesday there has been a shift from
previous forecasts. The low will move into Idaho increasing
northwesterly flow and bringing in cooler air. 500 mb ensemble
heights show one cluster with well above normal temperatures,
two with near normal, and one with below normal. While the
forecast once showed temperatures in the 90s for many valley
locations, the NBM has backed off and has brought in highs into
the 80s. With that said, there is still a 25% chance that highs
will exceed 90 degrees F in the Willamette Valley. Will
continue to monitor this as the pattern continues to resolve.
Minimal change on Thursday. -Muessle

&&

.AVIATION...Largely VFR conditions continue inland beneath areas
of cirrus debris tracking north and westward from convection
east of the Cascades. Sct low stratus developing along the
Cascade foothills may extend west toward the Willamette, Lower
Columbia, and Cowlitz Valleys early this morning, with up to a 30%
chance of MVFR cigs at KEUG from 14-17z Fri, and lower likelihood
to the north. Any low stratus will mix out by 16-18z Fri. Diurnal
winds build to 10-15 kt with gusts 15-25 kt out of the N to NW
this afternoon, easing to 5 kt or less tonight.

Along the coast, marine stratus will favor continued MVFR cigs
through 18-21z Fri, although there remains low chances (20-30%)
for periods of IFR cigs through 15z Fri. Sufficient clearing will
yield a return to VFR conditions this afternoon before MVFR
stratus redevelops by 00-03z Sat. Diurnal N to NW winds continue,
building to around 10 kt with gusts up to 20 kt this afternoon,
before easing to 5 kt or less tonight.

PDX AND APPROACHES...VFR conditions expected through the period.
Some low stratus may encroach from the east through the morning,
but coverage should remain low enough to maintain VFR conditions.
Chances for MVFR cigs remain around 20% from 14-17z Fri. Northwest
winds around 5 kt early will build to 8-12 kt gusting to 20 kt
after 18-21z Fri, then ease below 5 kt by 06-09z Sat. -Picard

&&

.MARINE...Persistent surface high pressure offshore will support
continued north to northwest winds across the waters. Diurnal
gusts will reach 10-15 kt north of Cape Falcon and 15-20 kt from
Cape Falcon to Florence both Friday and Saturday afternoon, easing
to around 10 kt each night while seas continue at 3-6 ft through
the weekend. Sunday into early next week, strengthening surface
high pressure will see winds increase to 20-25 kt and seas build
to 5-8 ft. -Picard

&&

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

$$

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