Cascade Locks, Oregon Weather Forecast Discussion

102
FXUS66 KPQR 062222
AFDPQR
Area Forecast Discussion
National Weather Service Portland OR
322 PM PDT Sat Sep 6 2025
.SYNOPSIS...After another round of showers and thunderstorms
this evening and overnight, expect a considerably cooler and
showery weather pattern through the first half next week.
&&
.SHORT TERM...through Tonight...Water vapor satellite imagery
reveals a large upper level low pressure over the eastern
Pacific. An embedded negatively tilted shortwave trough
currently centered over northern Oregon at the moment is
swinging northward into Washington. This feature helped kick off
last night`s thunderstorms that have since moved northward into
the Puget Sound.
In the immediate short term, doppler radar and visible satellite
imagery show thunderstorms developing in a region of 500-1000
J/kg of MUCAPE across far eastern Lane County. These storms
should remain near the crest with areas across the Cascade
foothills and southern Willamette Valley remaining capped this
afternoon due to the ongoing marine clouds and cooler surface
temperatures. High resolution models do suggest the cap will
erode farther north along the Cascade crest so some of these
storms appear likely to ride northward towards Mt Jefferson and
Mt Hood late this afternoon.
Another embedded shortwave trough is currently approaching the
northern California coast and is forecast to slide northward
across western Oregon and western Washington overnight. Large
scale lift ahead of this feature and elevated instability seem
likely to produce another round of convection based on the
pattern across western Oregon and Washington despite most
convective allowing models once again suggesting little to no
activity overnight. Suspect additional updates to the forecast
will be needed this evening as timing and placement of
convection becomes more certain.
.LONG TERM...Sunday through Friday night...Increasing
southwesterly to westerly flow should further scrub the region of
any lingering smoke except in the immediate vicinity of ongoing
wildfires. In general, most of the region will remain dry on
Sunday except for some areas of drizzle along the coast and a
few showers that bubble up over the Cascades before quickly
spreading east of the Cascades in the afternoon hours.
A cool, wet and showery Fall-like weather pattern develops
Monday and continues through at least Tuesday in response to a
closed upper level low that will settle over the region. This
low will bring widespread slow moving showers to the region. As
a result, precipitation amounts will be more patchy and random
in nature than many of frontal rain events. Nonetheless, the
NBM continues to show decent probabilities for at least
0.25-0.50" of rain over much of northwest OR and southwest WA
from the coast to the Cascades between 5 AM Monday and 5 AM
Wednesday. The NBM probabilities for the 0.25-0.50" of rain currently
range from 30-90% for that time period across the region. The
lowest probabilities are generally across the northwestern
portions of our CWA including much of southwest Washington, the
northern Willamette Valley and the north Oregon Coast Range. The
highest probabilities for the higher rainfall amounts is
currently found across the Lane and Linn County Cascades, which
should help slow wildfire activity. With the cloudy/showery
conditions in place, high temperatures will end up well below
average.
The forecast becomes more uncertain midweek onward. This
initially revolves around how quickly the aforementioned upper
low departs the region so showers could easily linger into
Wednesday across the area. Late in the week, 30-40% of the
ensemble guidance brings in another Fall-like trough into the
Pacific Northwest, which would maintain cool temperatures and
bring another good shot of rain to the region. The remaining
guidance suggests temperatures returning closer to seasonal
averages while keeping the area largely dry.
&&
.AVIATION...Currently MVFR/VFR conditions along the coast,
expected to deteriorate back to IFR/LIFR conditions around 03-06Z
Sunday. KAST has the best chances to stay MVFR/IFR during the TAF
period, with a 20-40% chance of IFR overnight and then a 60-80%
chance of MVFR through the rest of the period. As for KONP,
IFR/LIFR conditions will likely persist until 18-20Z Sunday
(40-60% chance of LIFR).
Inland, most terminals are under MVFR CIGs due to onshore flow
earlier this morning pushing marine stratus through the Coast
Range gaps and Columbia River. Expect these deteriorated inland
conditions to improve to VFR by 22-23Z Saturday. Low to moderate
confidence that MVFR CIGs will return to inland terminals by
11-13Z Sunday (20-40% chance of MVFR).
Additionally, there is potential for showers and isolated
thunderstorms this evening for inland locations, but confidence
for timing and location remains unclear at the moment. Any
thunderstorm activity that may develop will be moving in from the
south-southeast.
PDX AND APPROACHES...Expect current MVFR conditions to improve
to VFR by 22-23Z Saturday. VFR conditions will then continue
through the evening and drop back down to MVFR by 11-13Z Sunday
(30-50% chance of MVFR). There is potential for showers and
isolated thunderstorms this evening, but confidence for timing
and exact location remains unclear at the moment. Any thunderstorm
activity that may develop will be moving in from the south-
southeast. ~Hall
&&
.MARINE...An area of low pressure continues to progress through
the waters this weekend, maintaining southerly winds over the
waters. Expect these southerly winds to persist through Monday
and Tuesday before turning northerly again on Wednesday as the low
pressure moves off to the east and surface high pressure returns
to the waters. Additionally, there is a slight chances (15-20%)
for thunderstorms this evening. Seas will generally hold in the
3-5 ft range into early next week. There is a 30-40% chance of
combined seas climbing above 5 ft during the middle next week with
those probabilities climbing to 60-75% by the end of next week.
~Hall/Schuldt
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&
$$
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NWS PQR Office Area Forecast Discussion