548
FXUS66 KPDT 152300
AFDPDT

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

.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 /00Z TAFS THROUGH 00Z FRIDAY/...
Predominantly VFR conditions are currently forecast through the
TAF period, albeit with periods of showers, thunderstorms, and
breezy winds due to a low-pressure system that is churning just
offshore of the Pacific Northwest.

Showers and thunderstorms have initiated this afternoon in
central Oregon and are expected to track northward and expand
in coverage overnight into Thursday morning such that DLS and
YKM will also have chances of convection. Confidence in timing
is still shaky enough to have PROB30 groups instead of TEMPO or
prevailing showers.

High-resolution model guidance suggests potential for strong to
locally severe outflow winds this afternoon across central
Oregon with winds extending northeastward into south-central to
central Washington by this evening and tonight. Chances of
strong outflow are lower (<30% chance) for PDT/ALW in northeast
Oregon and southeast Washington.

&&

.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  62  93  57  90 /  20  20  10   0
ALW  67  97  63  92 /  20  20  10   0
PSC  66  99  62  95 /  20  20  10   0
YKM  67  97  60  94 /  70  40  10   0
HRI  67  96  61  93 /  20  20   0   0
ELN  64  93  57  89 /  70  50  10   0
RDM  55  87  47  90 /  30   0   0   0
LGD  61  97  58  93 /  20  30  20   0
GCD  58  97  55  95 /  20  10  10   0
DLS  65  85  59  89 /  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 WAZ691-694.
     Red Flag Warning until 10 AM PDT Thursday for WAZ695.
     Red Flag Warning from 8 PM this evening to 10 AM PDT Thursday
     for WAZ690.
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...86
FIRE WEATHER...82