Timberline Lodge

000
FXUS66 KPQR 111058
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
358 AM PDT Fri Sep 11 2026

.SYNOPSIS...A cool and unsettled weekend is ahead as an upper-level
low moves across the Pacific Northwest. Widespread rain and 
showers will develop Saturday and continue into Sunday, with 
temperatures remaining below seasonal average. A much warmer and
drier pattern then develops early next week as high pressure 
builds offshore.

&&

.DISCUSSION...Now through Thursday...Today will be a relatively
quiet day between weather systems, but temperatures will remain
cool compared to yesterday. Increasing clouds ahead of the next
system will limit afternoon warming, with highs reaching the 
upper 60s to low 70s across the interior and low to mid 60s near
the coast. Some interior valleys could also see patchy fog or 
low clouds this morning where skies remain clear, especially in 
areas with light winds and higher surface moisture.

The next system will become the main weather story this 
weekend. An upper-level low will deepen offshore tonight before 
moving across the region Saturday. Recent guidance continues to 
suggest that rain will reach the coast Saturday morning and 
spread inland through the afternoon. Rain and showers will 
continue Saturday night, followed by additional showers through 
most of Sunday. Confidence is high that most of the forecast 
area will see measurable precipitation, with most ensemble 
members supporting rain somewhere across the region.

Saturday through Sunday, total rainfall amounts should 
generally remain on the lighter side, with around 0.10-0.50 inch
expected for most locations. The Cascades will likely receive 
more, with the southwest Washington and north Oregon Cascades 
currently favored for the highest totals around 0.50-1.00 inch 
(highest values in the southwest Washington Cascades). Showers 
will become more scattered Sunday as the system moves east, 
although the higher terrain will continue to have the best 
chance for stratiform rain.

There is also a slight chance for thunderstorms (15-25% chance)
Saturday as the cold air associated with the upper-level low 
moves overhead. How much instability develops will depend partly
on the timing of the system. If the coldest air arrives later 
in the day, after daytime heating has weakened, thunderstorm 
chances will be lower. An isolated thunderstorm is still 
possible, however. Cold-core funnel clouds could also develop 
near the upper low. These are generally short lived and often 
remain above the ground, but a funnel reaching the surface 
cannot be completely ruled out.

The weekend system will also bring another noticeable drop in 
temperatures. Highs Saturday and Sunday will generally be in the
low to upper 60s across the interior. Conditions should 
gradually improve Sunday night as the low moves east and shower 
activity decreases.

A much warmer pattern is then expected to develop early next 
week as high pressure strengthens over the eastern Pacific. Some
lingering troughing could keep Tuesday from becoming completely
clear and warm, but the overall trend is toward drier weather 
and rising temperatures. Interior highs should climb into the 
mid to upper 70s by Tuesday.

By Wednesday, ensemble guidance favors the offshore ridge 
moving closer to the Pacific Northwest, with about a 75% chance 
of this scenario. If the ridge continues to build as expected, 
temperatures could reach the low to mid 80s across the interior 
lowlands. The other 25% of the guidance keeps some troughing 
near the region and would result in cooler temperatures. 
Increasing easterly flow is also possible by midweek as the 
ridge strengthens. Current guidance suggests the strongest winds
from Wednesday night into Thursday morning, with sustained 
winds of 15-20 mph and gusts 25-30 mph (isolated gusts up 35 
mph). With rising temperatures and lowering relative humidity 
Tuesday through Thursday and increased winds on Wednesday, this 
will definitely be something to monitor as the warmer pattern 
develops next week. ~12


&&

.AVIATION...Through 12Z Saturday...Expect primarily VFR
conditions through the TAF period. The only exception is from
now until 17Z Fri, where the potential for stratus formation
brings a 20-30% chance of MVFR CIGs at all terminals (VIS
included for coastal terminals). Conditions should improve back
to VFR by 17-18Z Fri. Otherwise, expect light and variable winds
early this morning to become 5-8 kt west to northwest winds in 
the afternoon.

KPDX AND APPROACHES...Currently high end MVFR CIGs (with
guidance suggesting a 20-30% chance of MVFR CIGs), which will 
likely improve back to VFR by 17-18Z as low stratus mixes out. 
Beyond 17-18Z Fri, expect VFR conditions through the TAF period.
Light and variable winds will become 4-6 kt northwest winds in
the afternoon.~12

&&

.MARINE...
Northerly winds continue across all waters today. Small Craft 
Advisories remain in effect through 8 AM PDT this morning 
across the outer waters (beyond 10 NM) due to marginally steep
seas of 6-8 ft at 9 seconds.

Another weaker system is expected to approach the coastal waters 
from the north tonight into Saturday. This will result in a 
southerly wind shift along with seas subsiding towards 4 to 6 ft
and gusts below 20 kts. A more active pattern is expected to 
return late Monday into Tuesday. This system looks to bring 
northerly winds back into the forecast with gusts approaching 20
kt. Seas are also expected to build towards 5 to 7 ft. ~12/42

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory until 8 AM PDT this morning for 
     PZZ271>273.
&&

$$

www.weather.gov/portland

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