972
FXUS66 KPDT 052239
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
339 PM PDT Sat Sep 5 2026

.KEY MESSAGES...
- An upper low will bring periods of showers this weekend,
  mainly over the mountains...with the best chances Sunday into
  Monday.

- Isolated thunderstorms chances (<25%) across the mountains
  through Monday.

- Drier conditions from later Monday onward.

&&

.DISCUSSION...
An upper low over the Pacific Northwest will slowly move
eastward through Sunday and by Monday will generally be east of
the area. The associated trough will gradually flatten and by
later Monday, the flow will become split across the region.
Ridging from the south will build in by midweek, before another
trough drops down for next weekend.

The persistent upper low will continue to bring unsettled
weather over the region, with periods of shwoers, mainly over
the mountains. The best time for more widespread showers looks
to be Sunday afternoon/evening into early Monday morning.

There will also be chances for isolated afternoon and evening
thunderstorms mainly during the afternoon and evenings,
especially over the mountains. By Monday afternoon,
precipitation chances shift generally from the Blue Mountains
eastward, and by later Monday generally east of the area.

QPF values have decrease a bit everywhere except along the
Oregon Cascade crest this afternoon/evening, where amounts are
generally >0.50 inches. Elsewhere amounts are generally less
than 0.25 inches. On Sunday into Monday, amounts are highest
over the Blue Mountains and pints eastward where amounts range
from 0.25 to 0.50 inches.

Temperatures remain 10 to 15 degrees below normal through the
weekend and the ECMWF EFI puts much of the area in the 0.7 to
0.8 below normal. On Sunday, much of the southern Oregon Blue
Mountains and portions of central Oregon are in the 80th to
90th percentile for precipitation as well, from the EFI.

Monday looks to be a bit breezy with winds 25 to 30 mph,
possibly as high as 35 mph in the Cascade Gaps, Columbia Basin,
Gorge, Simcoe Highlands and Kittitas Valley.

Beyond Monday, dry weather will move in as the trough moves east
of the region and the flow becomes more split and zonal. By
midweek, there will be some ridging moving in from the south.
Most of the week looks dry with more seasonable temperatures.

Another trough looks to approach toward the end of the week and
will bring precipitation chances again, mainly to the mountains.
This trough looks to be progressive and moves through rather
than lingering in place.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Radar advertises showers pushing through the area with some TAF
sites experiencing precipitation. Nothing heavy with the precip
as it`s mostly light to moderate. Showers will dissipate in the
overnight hours but will re-develop in the day time hours
tomorrow. Some of the heaviest rain is expected across BDN and
RDM, especially in the afternoon hours. Confidence isn`t high
enough to put in MVFR or below conditions, but both BDN and RDM
have a 10 to 20 percent chance of seeing some MVFR or below
conditions develop when the heaviest rain enters. Elsewhere,
those chances drop down to 5 to 10 percent.

&&

.Preliminary Point Temps/PoPs...
PDT  45  68  48  73 /  10  30  40  30
ALW  50  71  52  73 /  10  10  60  50
PSC  48  73  50  77 /   0  20  30  20
YKM  51  72  52  78 /  10  30  10   0
HRI  49  71  50  76 /  10  30  30  20
ELN  45  71  48  72 /  10  20  20   0
RDM  40  61  37  67 /  60  90  50   0
LGD  43  72  46  69 /  10  50  80  70
GCD  45  69  46  69 /  10  70  80  20
DLS  55  71  55  74 /  30  50  10   0

&&

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

&&

$$

DISCUSSION...77
AVIATION...95