765
FXUS66 KPDT 221137
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
437 AM PDT Wed Jul 22 2026

.KEY MESSAGES...
- Hot temperatures remain possible through Thursday, but smoke
  and remnant cloud cover may limit daytime heating potential

- Monsoonal moisture push with shortwave impulses will result in
  a return of isolated to scattered thunderstorm activity across
  central OR and the northeast OR mountains

- Upper level troughing offshore will produce breezy winds in
  the Cascade Gaps and Columbia Basin late Thursday into the
  weekend

&&

.DISCUSSION...Nighttime satellite imagery tonight shows cloudy
conditions across the eastern mountains, with partly cloudy to
mostly clear conditions elsewhere. While smoke continues to hang
around the forecast area, surface observations tonight show
that smoke has become "lighter", with most stations reporting
visibility greater than 6 miles and few to scattered ceilings.

Sensible weather concerns through Thursday continue to revolve
around a strengthening upper level ridge producing hot
temperatures in and around the Columbia Basin; daily shortwave
impulses riding up the ridge will tap into monsoonal moisture
and increasing instability, producing isolated to scattered
thunderstorms in the afternoons and evenings.

Through Thursday, the PacNW will remain under the influence of
a gradually strengthening upper level ridge of high pressure
while a deep southerly flow persists aloft. This will introduce
increasingly hot temperatures across the lower elevations, with
the brunt of the heating expected in the Columbia Basin/Gorge
and adjacent foothills/valleys through Thursday afternoon.
Portions of the OR/WA Columbia Basin and the eastern Gorge are
forecast to see high temperatures between 100 to 103 degrees
this afternoon, with the Blue Mountain foothills,
Yakima/Kittitas valleys, portions of north central Oregon, and
portions of the John Day Basin reaching around 100 degrees
(confidence 60-85%). While model guidance depicts the warming
temperatures, regional smoke density continues to invite
uncertainty in the effectiveness of daytime heating. Model
guidance struggled with the impacts of smoke the past couple
days, with yesterday`s afternoon temperatures about 2 to 3
degrees below the forecast. With smoke expected to continue
impacting portions of the region today and Thursday, there is
moderate confidence (45-55%) that those areas(portions of the
Blue Mountain Foothills, Columbia Basin, central OR, and eastern
mountains) under denser smoke will see their afternoon
temperatures about 2-3 degrees lower than what is forecast. Hot
temperatures will continue in most areas Thursday, however
increasing winds through the Cascade Gaps late afternoon will
limit heating through the eastern Gorge and the Kittitas valley
(confidence 65-80%). Between elevated afternoon and overnight
temperatures, HeatRisk values across much of the lower
elevations will be in the moderate to major categories,
resulting in the Heat Advisories across the Columbia
Basin/Gorge, Yakima Valley, and the northern Blue Mountain
foothills.

Through Thursday, ensemble and deterministic guidance depicts a
monsoonal moisture push riding the southerly flow into the
intermountain PacNW, with daily PWATs around 0.75 to 1.25
inches. Weak shortwave impulses riding up the southerly flow
will tap into the moisture and increasing instability to help
initiate isolated to scattered thunderstorms. Today, the main
thunderstorm activity will be focused across central OR and the
mountainous terrain from the Cascade east slopes to the Ochoco
mountains. In these areas, MUCAPE will be between 500-1000J/kg,
low level lapse rates 8-10 C/km, and 0-6km shear between
20-40kts. These conditions will be more than enough for
thunderstorms to develop in the afternoon and become organized
as they propagate north. By Thursday, similar conditions will be
present along the WA Cascades, Blue Mountains, and Wallowa
county. Expect at least small hail, gusty outflow winds,
frequent lightning, and a few storms to produce heavy downpours.

Late Thursday through the weekend, there is good agreement
amongst ensemble cluster guidance that upper troughing will
develop off the coast of the PacNW while upper level ridging
pushes east and south. Southwest flow aloft will prevent
monsoonal moisture from advecting into the region, resulting in
drying conditions across the forecast area. The proximity of the
upper trough late Thursday into Friday will also result in
breezy west to northwest winds(15-25mph with gusts 25-35mph)
through the Cascade gaps and across the Columbia Basin.
Saturday, a shortwave will eject across northwest WA into BC,
bringing breezy to windy conditions (gusts up to 50mph) through
the Cascade gaps, with breezy conditions across the remainder of
the forecast area. Friday, there is moderate confidence
(55-65%) that peak winds will overlap with critically low RHs
in portions of the Columbia Basin and Cascade Gaps. On Saturday,
there is moderate confidence (40-55%) winds and low RHs will
overlap in areas of the Columbia Basin and eastern mountains.
Otherwise, the shortwave passage will also result in light rain
showers developing along the WA Cascade crest through Sunday
morning (confidence 50-65%). Sunday through Tuesday, the
forecast area will remain under a mild, dry southwest flow aloft
with diurnally driven breezy winds, near to below normal
temperatures, and dry conditions (confidence 45-60%). Lawhorn/82

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...Mix of conditions
across the region through the period. Smoke will continue to
bring MVFR or lower vsby/CIG impacts to sites PDT/ALW/RDM/BDN
this morning, with conditions expected to improve to VFR by the
afternoon. At least rain showers are expected to impact sites
RDM/BDN this afternoon and evening, with a Prob30 chance that
the sites are impacted by thunderstorms with variable gusty
outflow winds between 22-03Z. There is also a Prob30 chance of
showers at site DLS between 00Z-04Z. Winds will increase at site
DLS around 04Z to 12-20kts with gusts up to 30kts possible
through the end of the period. Winds will otherwise remain light
at all other sites through the period. Lawhorn/82


&&

.FIRE WEATHER...Conditions will remain hot and dry through
Thursday, with hottest conditions in the Columbia Basin and
adjacent foothills/valleys. However, areas under heavy smoke
will see less heating than anticipated. Monsoonal moisture and
increasing instability will bring isolated to scattered
thunderstorm chances through Thursday. Today, chances (20-50%)
will be focused across central OR, OR Cascades, and Ochocos.
Chances (15-35%) Thursday will be focused along the WA Cascade
crest, Blue Mountains, and Wallowa county. Thunderstorms will be
capable of frequent lightning, gusty outflow winds, small hail,
and brief heavy downpours. Winds will increase through the
Cascade Gaps and Columbia Basin Friday, and are expected to
overlap with near to critically dry conditions, resulting in
elevated fire weather conditions. A weak system passage Saturday
may result in breezy conditions area wide, with peak winds
overlapping with critically low RHs in the eastern mountains and
portions of the Columbia Basin in the afternoon. Lawhorn/82

&&

.Preliminary Point Temps/PoPs...
PDT  99  67  96  63 /   0   0  10   0
ALW 102  72  99  69 /   0   0  10  10
PSC 103  70 101  65 /   0   0   0   0
YKM 102  72 100  64 /   0  10  10   0
HRI 103  71  98  66 /   0   0   0   0
ELN 100  69  95  61 /   0  10  10   0
RDM  95  59  93  55 /  40  40   0   0
LGD  99  67 100  63 /   0   0  30  10
GCD  97  63  99  59 /  10  10  10   0
DLS 104  71  91  65 /   0  10  10   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory until 9 PM PDT Thursday for WAZ024-027>029.
     Air Quality Alert until 9 AM PDT this morning for WAZ028>030.
OR...Heat Advisory until 9 PM PDT Thursday for ORZ041-044-507.
     Air Quality Alert until 4 PM PDT this afternoon for ORZ044-049-
     050-502-503-505>509-511.
     Red Flag Warning from 11 AM this morning to 11 PM PDT this
     evening for ORZ698-700-705.

&&

$$

DISCUSSION...82
AVIATION...82
FIRE WEATHER...82