836
FXUS66 KPDT 160540
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1040 PM PDT Wed Jul 15 2026

.Updated Aviation Discussion.


.KEY MESSAGES...
- Isolated to scattered thunderstorms through Thursday night
  across northeast Oregon and southeast Washington

- Critical fire weather conditions from abundant lightning and
  outflow winds through Thursday night

- Moderate to locally major HeatRisk through Thursday, and a
  return of widespread moderate HeatRisk Sunday into next week.

&&

.DISCUSSION...
Today through Thursday: Satellite and radar imagery shows
plenty of activity across the mountains this afternoon, with
widely scattered thunderstorms developing across the OR Cascades
and ElkHorn Crest down to the Strawberries. Meanwhile, an
isolated thunderstorm has developed in far northwest Yakima
county, well ahead of the incoming system.

Through tomorrow morning, a shortwave impulse currently lifting
across northeast OR will continue to initiate isolated to
scattered thunderstorms, with main activity expected to ride up
the Cascade east slopes through tonight. A few isolated
thunderstorms will also remain possible across the eastern
mountains into northern Wallowa county. With plenty of surface
moisture in place (pwats up to 1.2 inches), dry mid-layer
(inverted V-sounding profile), steep mid-level lapse rates, and
MUCAPE up to 1000J/kg, a few thunderstorms will have the
potential to produce strong to severe outflow gusts (50 to 60
mph) this afternoon into this evening. Expect moderate to
locally heavy downpours(0.25 to 0.4 inches/hr) with these
stronger storms as well.

Thursday, an upper low offshore will cut across northwest WA as
it kicks north. This upper low will cause a moderate pressure
gradient to develop across the Cascades, leading to breezy
winds (25 to 40mph gusts) through the Cascade gaps (confidence
65-75%). However, the low will also bring cooler temperatures
west of the Cascades, creating a strong thermal gradient (20-30
degrees F) between the Columbia Basin and I-5 corridor, which
will aid in strengthening winds through the gaps. Otherwise,
another shortwave impulse rotating north across far eastern
OR/WA will bring another round of isolated thunderstorms from
the Strawberry mountains, to the northern Blues in WA (including
Wallowa County). A strong thunderstorm or two will also be
possible with activity tomorrow, as MUCAPE will be 500-1000
J/kg, with moderate mid-level lapse rates (7-8 C/km) and low
level sheer between 20-30kts. Expect outflow winds and heavy
downpours to be the main threats.

Friday through Sunday: Dry conditions will redevelop across the
area as upper level riding begins to build into the PacNW from
the east. Winds will become light and diurnally driven across
the area. Behind the low exit Thursday, temperatures will drop
about 3 to 5 degrees across the area, resulting in mainly low to
mid 90s in the Columbia Basin. However, with the ridge building
back over the weekend, expect temperatures to warm 1 to 2
degrees day to day, with a return of the upper 90s in the Basin
by Sunday.

Monday and Tuesday: Fairly good agreement amongst ensemble
cluster solutions of weak troughing/low pressure develop
offshore the PacNW while upper level ridging amplifies poleward.
This will bring a deep south to southwest flow into the area,
resulting in increased instability and monsoonal across the
intermountain PacNW (confidence 50-60%). As a result, the
mountains and central OR will see a return of at least isolated
thunderstorm chances through Tuesday. The southerly flow will
also bring increased temperatures across the rest of the region,
with NBM showing a 35-55% chance of breaking the 100 degree mark
in the Columbia Basin Monday and Tuesday. Lawhorn/82

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
VFR conditions currently across all sites, which will stay the
course through the period. However, slight chances of
showers and thunderstorms exist for KYKM through the early
morning hours that may briefly drop ceilings or visibilities
near MVFR conditions, as well as cause breezy winds of up to
25kts. Breezy winds are also expected at most sites, gusting
between 20-30kts late Thursday afternoon and evening. Exceptions
for KALW/KPSC, as winds at or below 10kts are likely. A marine
push will cause KDLS to be breeziest, with gusts of 30-35kts.
Ceilings will lift from 10kft to 25kft tomorrow afternoon. 75

&&

.FIRE WEATHER...
Main threat through Thursday will be strong isolated
to scattered thunderstorms developing across the Cascades,
eastern mountains, western portions of the Columbia Basin, and
the Yakima/Kittitas valleys. With unseasonably dry fuels in
place, thunderstorms with frequent lightning will produce a
critical fire weather threat. Breezy winds will develop through
the Cascade gaps tomorrow afternoon, but an associated marine
push will keep fire weather conditions from becoming critical.
Warm and dry conditions develop Friday into the weekend, with
isolated thunderstorm threat returning early next week.

&&

.Preliminary Point Temps/PoPs...
PDT  66  93  56  89 /  20  20   0   0
ALW  69  98  63  92 /  20  20  10   0
PSC  70  99  61  94 /  30  20   0   0
YKM  69  97  60  94 /  70  40   0   0
HRI  69  95  60  93 /  20  20   0   0
ELN  65  94  56  88 /  70  50   0   0
RDM  57  87  47  89 /  20   0   0   0
LGD  64  98  59  93 /  20  30  20   0
GCD  61  98  55  95 /  20  10   0   0
DLS  66  83  59  88 /  70  20   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory until 5 AM PDT Thursday for WAZ024.
     Heat Advisory until 9 PM PDT Thursday for WAZ026>029.
     Red Flag Warning until 10 AM PDT Thursday for WAZ690-691-694-
     695.
OR...Heat Advisory until 5 AM PDT Thursday for ORZ041.
     Red Flag Warning until 5 AM PDT Thursday for ORZ691.
     Heat Advisory until 9 PM PDT Thursday for ORZ044-049-050-507.
     Red Flag Warning until 11 PM PDT this evening for ORZ700-
     703>705.

&&

$$

DISCUSSION...82
AVIATION...75
FIRE WEATHER...82