223
FXUS66 KPDT 100529
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1029 PM PDT Sat Aug 9 2025

.Updated Aviation Discussion.


.AVIATION...06Z TAFS...VFR conditions currently across all sites,
which will stay the course through the period. Clear skies and
light, diurnally-driven winds below 11 kts is expected to persist.
75


&&


PREV DISCUSSION... /issued 106 PM PDT Sat Aug 9 2025/

DISCUSSION...
North to northwest flow over the Pacific Northwest will
move eastward through tonight. Then, a large area of high pressure
will move over the region and be the dominant feature through
early next week.

This high will bring increasingly hot temperatures through the
Monday/Tuesday timeframe. As a result, Excessive heat warnings are
being issued for most of the lower elevation locations. High
temperatures on Sunday will be in the mid to upper 90s in many
areas, with 100 not being ruled out across the Colombia Basin and
Gorge and Yakima Valley. On Monday and Tuesday, the Columbia
Basin, Gorge, Yakima Valley, Blue Mountain Foothills and portions
of central Oregon should be 100 to 104.

HeatRisk values will be widespread moderate Sunday, and widespread
moderate Sunday, with major across the Columbia Basin, Gorge,
Yakima and Kittas Valley Blue Mountain Foothills and portions of
Central Oregon. Tuesday will also see widespread Moderate HeatRisk
with major across many of the same areas.

High temperatures will be 10 to 15 degrees above normal and low
temperatures will remain in the 60s and may not get much below 70
degrees in portions of the Columbia Basin, Gorge and Foothills of
the Blue Mountains.

By Monday and Tuesday the ECMWF EFI have anomalies of 0.7 to 0.8
for high and low temperatures, mainly across the Basin, but 0.6 to
0.7 elsewhere across the region. NBM probabilities of high
temperatures >=100 are >80 percent in many areas come Monday and
Tuesday.

The ridge is suppressed south later Tuesday into Wednesday and
the area gets into a more westerly flow. This will bring a gradual
cool down beginning Wednesday through the wend of the week.

More importantly, it will bring breezy to windy conditions
especially later Tuesday into Wednesday, especially for the
Cascade gaps, Colombia Basin, Gorge and Foothills of the Blue
Mountains. With RH values expected to be <20 percent, enhanced and
even critical fire weather conditions are possible.

As temperatures further decrease Thursday and remain close to
seasonal through the end of the week, RH values will rise and
winds will also decrease, though it will remain locally breezy.
This should help alleviate fire weather concerns.

The next chance of any precipitation looks to be Friday or
Saturday, and the rain would be confined to the Washington
Cascades, at best.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  59  95  64 100 /   0   0   0   0
ALW  65  95  70  99 /   0   0   0   0
PSC  61  97  65 101 /   0   0   0   0
YKM  63  97  66 101 /   0   0   0   0
HRI  60  97  65 102 /   0   0   0   0
ELN  61  96  65  98 /   0   0   0   0
RDM  51  95  55  99 /   0   0   0   0
LGD  56  92  60  97 /   0   0   0   0
GCD  55  93  59  98 /   0   0   0   0
DLS  67 100  71 103 /   0   0   0   0

&&

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

WA...Extreme Heat Warning from noon Sunday to 10 PM PDT Tuesday for
     WAZ024-026>029-521.

&&

$$

DISCUSSION....77
AVIATION...75