295
FXUS66 KPDT 231725
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1025 AM PDT Thu Jul 23 2026

.KEY MESSAGES...
- Hot temperatures will continue to bring areas of Major
  HeatRisk today, but area smoke may limit daytime heating
  potential

- Shortwave impulse today will tap into monsoonal moisture and
  increased instability to produce isolated to scattered
  thunderstorms across the Blue mountains to the ID border

- Upper level troughing offshore will produce breezy winds in
  the Cascade Gaps and Columbia Basin late this afternoon
  through the weekend.

&&

.DISCUSSION...
Satellite imagery tonight shows remnant cloud
cover from earlier convective activity over far eastern OR/WA
and across the WA Cascades, while radar does show light showers
about to exit the central WA Cascade crest at this time. At the
surface, moderate to heavy smoke is impacting areas of central
OR, mountain valleys across the Blues, and the Blue mountain
foothills.

Sensible weather concerns today continue to revolve around a
an upper level ridge over the PacNW producing hot temperatures
in and around the Columbia Basin; another shortwave impulse
riding up the ridge will tap into monsoonal moisture and
increasing instability, producing isolated to scattered
thunderstorms from the Blue mountains to the ID border.

Today, the PacNW will remain under the influence of an upper
level ridge of high pressure while a deep southerly flow
persists aloft. Hot temperatures will continue across the lower
elevations, with the brunt of the heating expected in the
Columbia Basin/Gorge and adjacent foothills/valleys this
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 70-90%). While model guidance depicts the warming
temperatures, regional smoke density and timing of winds through
the Cascade gaps increase uncertainty in the effectiveness of
daytime heating. Between elevated afternoon and overnight
temperatures, HeatRisk values across much of the lower
elevations will be in the moderate to major categories again
today, resulting in Heat Advisories through this evening across
the Columbia Basin/Gorge, Yakima Valley, and the northern Blue
Mountain foothills.

Monsoonal moisture will continue to linger across the PacNW
through this evening, with PWATS between 0.75 to 1.25 inches. A
weak shortwave impulse 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 areas of the Blue
mountains to the ID border. Conditions in these areas will be
favor thunderstorm activity, with MUCAPE between 500-1250J/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 northeast. Expect at least small hail, gusty
outflow winds, frequent lightning, and a few storms to produce
heavy downpours.

Later today 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 later today 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 (60-75%)
that peak winds will overlap with critically low RHs in portions
of the Columbia Basin and Cascade Gaps. On Saturday, there
remains moderate confidence (60-70%) 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 55-65%). Sunday through Wednesday, 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 55-60%).
Lawhorn/82

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...MVFR to VFR conditions
continue with lingering smoke/haze impacting area terminals.
Increasing west to northwest winds of 10-15 kts with gusts up to
25 kts anticipated for KDLS, KPDT, KRDM, and KBDN by 20z. These
winds could improve visibilities at those terminals through the
evening hours, with visibilities potentially decreasing again
through early morning hours of Friday. Branham/76

&&

.FIRE WEATHER...
Hot and dry conditions remain across the region
today, especially across the Columbia Basin and adjacent
valleys/foothills. Lingering monsoonal moisture and increased
instability will result in another round of isolated to
scattered thunderstorms this afternoon and evening, with chances
(20-50%) focused from the Blues mountains to the ID border.
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 low RHs,
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  96  61  96  61 /   0   0   0   0
ALW  99  68  99  67 /   0   0   0   0
PSC 101  66 100  66 /  10   0   0   0
YKM 100  64  99  64 /  10   0   0   0
HRI  99  65  99  66 /  10   0   0   0
ELN  94  61  94  60 /  10   0   0   0
RDM  93  56  95  54 /   0   0   0   0
LGD  99  62 100  61 /  60   0   0   0
GCD  99  58 100  57 /   0   0   0   0
DLS  91  65  96  64 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory until 9 PM PDT this evening for WAZ024-027>029.
     Red Flag Warning until 9 PM PDT this evening for WAZ693.
     Red Flag Warning until 7 PM PDT this evening for WAZ692.
     Air Quality Alert until 9 AM PDT Friday for WAZ028>030.
OR...Heat Advisory until 9 PM PDT this evening for ORZ041-044-507.
     Air Quality Alert until noon PDT Friday for ORZ044-049-050-502-
     503-505-506-508-509-511.
     Red Flag Warning until 8 PM PDT this evening for ORZ694-695-
     697>699.
     Red Flag Warning until 9 PM PDT this evening for ORZ693.
     Red Flag Warning until 7 PM PDT this evening for ORZ692.

&&

$$

DISCUSSION...82
AVIATION...76
FIRE WEATHER...82