009
FXUS66 KPDT 111739
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1039 AM PDT Mon Aug 11 2025

.Updated Aviation Discussion.


.AVIATION...18Z TAFS...VFR conditions currently across all sites,
which will stay the course through the period. High pressure ridge
continues to bring clear skies and diurnally-driven winds across all
terminals. 75


&&



PREV DISCUSSION... /issued 108 PM PDT Sun Aug 10 2025/

DISCUSSION...
Strong high pressure will build over the Pacific Northwest today
and remain over the area through Monday before getting pushed
southward on Tuesday. By later Tuesday a more zonal westerly flow
will move into the region and remain for the rest of the week.

The ridge of high pressure will bring very hot temperatures to the
area, beginning today and peaking Monday and Tuesday. Extreme heat
warnings are in effect and most lower elevation locations will be
in moderate HeatRisk today. Moderate HeatRisk becomes more
widespread Monday and Tuesday with portions of the Columbia
Basin, Blue Mountain Foothills, Yakima and Kittitas Valleys,
Columbia Gorge and and central Oregon reaching Major HeatRisk.

High temperatures could top out in the 102-103 range in the
hottest locations. These would be about 15 degrees above normal.
The ECMWF EFI does key in on the temperatures, with values mainly
in the 0.7 to 0.8 range, especially across the Basin.

After Tuesday, we will see a gradual cool down, with Wednesday
being about 10 degrees cooler than Tuesday (but still above
normal) and Thursday through the remainder of the period having
high temperatures near seasonal levels, generally in the 80s.

Winds are expected to increase as the ridge breaks down Tuesday
and continue into Wednesday. It will be breezy to windy,
especially later Tuesday into Wednesday, with breezy conditions
continuing into Thursday. Low RH values, especially on Tuesday and
Wednesday will lead to enhanced and possibly critical fire
weather concerns. The lower temperatures Thursday onward will help
raise humidities and lower winds after Thursday will also help
decrease concerns beyond then. The ECMWF EFI is picking up the
increased winds on Wednesday, especially across the Columbia
Basin and Foothills of the Blue Mountains, with values of 0.7 to
0.8, mainly.

No precipitation is expected until Friday into Saturday, and then
only over the mountains.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  99  66 100  68 /   0   0   0   0
ALW  99  71 100  73 /   0   0   0   0
PSC 101  66 102  67 /   0   0   0   0
YKM 100  70 102  66 /   0   0   0   0
HRI 102  66 102  70 /   0   0   0   0
ELN  98  67  98  66 /   0   0   0   0
RDM 100  57  99  55 /   0   0   0   0
LGD  98  62  98  62 /   0   0   0   0
GCD  98  62  99  60 /   0   0   0   0
DLS 103  72 100  70 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Extreme Heat Warning until 10 PM PDT Tuesday for ORZ041-044-505-
     507-508-510-511.

WA...Extreme Heat Warning until 10 PM PDT Tuesday for WAZ024-026>029-
     521.

&&

$$

DISCUSSION....77
AVIATION...75