235
FXUS66 KPDT 011140
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
440 AM PDT Tue Sep 1 2026

.KEY MESSAGES...

- A series of upper level low pressure systems will bring
  periods of rain, breezy westerly winds, and isolated
  thunderstorm chances through Friday.

&&

.DISCUSSION...

Upper ridging at 500 mb will shift to a southwesterly flow
aloft Today as and eastern Pacific trough shifts toward the
WA/OR coast. The EC/GFS/HiRes models all show the lead shortwave
spreading into nrn CA Tonight and northward toward the Snake
River by midday Wednesday. Temperatures today look cooler by
about 5 to 10 degrees across the gaps, central Oregon and warmer
by about 5 degrees across the Yakima valley and parts of the
Columbia Basin of Washington. More sky cover is expected today
ahead of a changing synoptic pattern, however some periods of
sun are forecast by NBM transitioning through the afternoon.
Breezy to windy westerly surface winds across the central Oregon
zones, Eastern Columbia Gorge, Simcoe highlands and the
Kittitas valley can linger into the evening and overnight given
the surface pressure gradients. The breezy winds, shift west
southwest through late Wednesday as the initial shortwave
spreads east of the region and the parent upper pacific low
moves onshore Thursday night.

The pattern will bring a transition to wet conditions for
midweek. For This afternoon, the HREF calibrated 4-hr
probability of thunder is limited to a 10 to 25 percent chance
range between about 20z and 03z over eastern Wallowa county and
even lower chances for the same geographic area on Wednesday
afternoon, so a low confidence forecast of isolated dry
thunderstorms. Precipitation chances increase from there as the
48 hour expected NBM precipitation would put about one third to
three quarters of an inch of rain by Wednesday
overnight/Thursday morning. The extended period of the forecast
looks near to cooler than normal and wetter than normal as the
aforementioned upper low lingers over the PAC NW and Interior NW
through around Tuesday or Wednesday of next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...

Scattered to broken high clouds across the region will continue
Today with no expectations for lower ceilings developing. Most
windy location will be DLS where gusts of of 25 to 30 kts will
be common into the overnight. Breezy west to southwest winds at
PDT developing in the mid afternoon. Light variable winds at BDN
and RDM this morning turn the typical north in the early
afternoon.

&&

.Preliminary Point Temps/PoPs...
PDT  83  49  75  48 /  10  10  30  80
ALW  84  55  77  52 /  10  10  30  90
PSC  87  54  78  47 /  10   0  10  70
YKM  88  55  75  49 /  10   0  20  50
HRI  87  54  78  48 /  10  10  20  70
ELN  84  50  72  44 /   0   0  30  70
RDM  80  40  67  37 /  10  10  70 100
LGD  86  50  73  47 /  20  20  70 100
GCD  88  51  73  48 /  10  10  30 100
DLS  81  57  72  52 /   0   0  80  90

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...Air Quality Alert until 10 AM PDT Wednesday for WAZ026-522-523.
OR...Air Quality Alert until noon PDT Wednesday for ORZ041-505-506-
     509>511.

&&

$$

DISCUSSION...71
AVIATION...71