576
FXUS66 KPDT 070433
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
933 PM PDT Sun Sep 6 2026

.KEY MESSAGES...
- Shower and thunderstorm chances through this evening, with
  decreasing chances on Monday.

- Dry weather through much of the week with seasonable
  temperatures.

- Potential for another upper trough and precipitation next
  weekend.

&&

.DISCUSSION...
The persistent upper low that has been over the Pacific
Northwest will begin to move eastward tonight and will be well
east of the region on Monday. However, some troughing will
remain over the area and will keep unsettled conditions, mainly
over the eastern Oregon mountains on Monday, with everywhere
else remaining dry.

By Tuesday, and through much of the week, the area will be under
a split flow regime, with a more westerly flow moving in by
Thursday.

On Friday, another upper low will drop down from the northwest,
and bring another chances of showers, and possibly some
thunderstorms, mainly to the mountains. This low will cross the
region on Saturday and exit on Sunday. Unlike the current low,
this looks to be a fast moving progressive low.

Latest radar showed isolated to scattered showers. Satellite
imagery showed abundant cloud cover and many areas were
struggling in the 50s and lower 60s, though the Columbia Basin
was close to 70 degrees. Cloud cover is affecting thunderstorm
development, but if we are able to get some sufficient breaks
later this afternoon, the most likely areas for thunderstorm
development would be from the northern Blue Mountains eastward.


In areas of heavy rain, the could be 0.25 to 0.50 inches, but
most places will see less than 0.25 inches.

Monday will see breezy winds, in the 25 to 30 mph range,
possibly as high as 35 mph across the Cascade Gaps, Kittitas
Valley, Simcoe Highlands and the Columbia Basin and Gorge.

Another breezy period will be Thursday across the same areas in
advance of the next trough winds will be similar (possibly a bit
higher), though RH values will be lower on Thursday. Areal
coverage of wind gusts are a bit more on Thursday while
probabilities of wind gusts >= 25 mph >80 percent both days.

High temperatures will remain 10 to 15 degrees below normal on
Labor day before rising to near seasonal normals for much of the
week. Highs will ten drop below normal again Friday and Saturday
as the next trough moves through. the ECMWF EFI has 0.8 to 0.9
below normal for Monday across mainly central and eastern
portions of Oregon.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...

Ceilings near but not over the PDT ALW terminals due to cool
moist boundary layer as the rains end and the fact that the HREF
is printing low vsbys in the adjacent foothills. Guidance, both
climate and HREF keep the terminal vicinities clear with light
south to southwest winds overnight. NO chances for impacts
elsewhere. Surface winds will increase marginally to 10 to 15
knots through the Gorge/Blue Mt Foothills terminals
(DLS/PDT/PSC/ALW) Monday afternoon with gusts commonly in the 20
to 25 knot range).

&&

.Preliminary Point Temps/PoPs...
PDT  47  71  42  75 /  20  10   0   0
ALW  51  73  49  77 /  40  20   0   0
PSC  50  76  46  79 /  10   0   0   0
YKM  52  76  48  78 /  10   0   0   0
HRI  50  74  45  78 /  10   0   0   0
ELN  48  71  45  77 /  20   0   0   0
RDM  37  68  38  75 /  20   0   0   0
LGD  45  68  42  74 /  90  20  10   0
GCD  44  67  41  76 /  90  10   0   0
DLS  53  74  51  80 /  30   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...None.
OR...None.

&&

$$

DISCUSSION...77
AVIATION...71