594
FXUS66 KPDT 160439
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
939 PM PDT Sat Aug 15 2026

.KEY MESSAGES...

- Lower (<20 percent) chances of showers and thunderstorms
  Sunday and a 20-30 percent chance of showers Monday with a
  (<20 percent) chance of thunderstorms mainly from the Blue
  Mountains eastward.

- Increasing winds later Monday into Tuesday.

&&

.DISCUSSION...issued at 200 PM PDT Sat Aug 15 2026...
Southwesterly flow remains over the Pacific Northwest. Low
pressure will move from near British Columbia to well off the
Oregon and California coasts by Monday afternoon. This will
allow for a more split flow pattern to develop early next week,
which should keep things dry. A ridge will build back over the
area by midweek, with a return to southwest or south flow
possible thereafter.

The showers and thunderstorms that affected portions of the
Columbia and Blue Mountain foothills earlier have weakened and
were moving out of the area. Additional showers and
thunderstorms were expected to develop mainly from the Blue
Mountains eastward this afternoon. Any thunderstorms could
contain gust winds and abundant lightning. A Red Flag Warning
remains in effect for mainly the eastern Oregon Mountains
through this evening.

The model guidance is in reasonable agreement that thunderstorm
activity on Sunday will be significantly less and further east.
While isolated activity can not be ruled out, especially over
Wallowa County, it does not appear to be widespread enough to
warrant any kind of additional headlines. Activity could
possibly be a bit higher on Monday, but looks to be mainly over
Wallowa County.

As we go from Monday into Tuesday, a split flow develops and
winds will increase across the area. There will be some
gustiness developing Monday evening, but the better chances are
Tuesday afternoon across the Cascade gaps, Kittitas Valley,
Simcoe Highlands, Columbia Basin and Gorge. Winds could gust 20
to 30 mph in these areas. RH values will also decrease from
Monday into Tuesday. NBM probabilities of wind gusts >= 25 mph
are >70 percent in these areas. However, with the exception of
the Kittitas Valley, NBM probabilities of wind gusts >=39 mph
are less than 40 percent. Will need to see how these winds
evolve over the next few days to see if any headlines will be
needed, but fire weather concerns will at least be elevated.

The midweek period looks dry before the south or southwest flow
returns and an upper low comes into play as well. All of these
features could bring additional chances of precipitation by the
end of the week.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
VFR conditions are forecast at all sites through the period.
Winds will become breezy at DLS again Sunday afternoon.
Elsewhere, lighter winds are forecast, albeit with some
afternoon gustiness, especially at RDM/BDN. Precipitation
chances are very low (10 percent or less) at all sites on
Sunday.

&&

.FIRE WEATHER...
For Sunday and Monday, thunderstorm chances will be less (<20
percent) and mainly confined to these same areas, though chances
could be a bit higher on Monday than Sunday. At this time,
there are no plans to extend the Red Flag Warning or issue
another one for Sunday due to the lower probabilities and much
less areal coverage. Current thinking is no headlines will be
needed for Monday either, but will reevaluate that with each
subsequent model run.

The next concern then becomes gusty winds later Monday into
Tuesday, which could be in the 25 to 30 mph range, coupled with
decreasing humidities. Fire weather concerns will be elevated,
but will need to see how things do or don`t come together for
any weather headlines.

&&

.Preliminary Point Temps/PoPs...
PDT  56  88  57  89 /  10   0   0   0
ALW  62  89  63  90 /  20   0   0   0
PSC  57  93  60  93 /   0   0   0   0
YKM  60  91  61  93 /  10   0   0   0
HRI  60  91  61  92 /   0   0   0   0
ELN  58  86  59  89 /  10   0   0   0
RDM  49  87  51  88 /  10   0   0   0
LGD  54  89  57  91 /  20  10   0  10
GCD  54  91  56  91 /   0   0   0   0
DLS  63  89  61  92 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...Air Quality Alert until noon PDT Monday for WAZ026-522-523.
OR...Air Quality Alert until noon PDT Monday for ORZ041-503-505-506-
     508>511.

&&

$$

DISCUSSION...77
AVIATION...86
FIRE WEATHER...77