972
FXUS66 KPDT 151820
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1120 AM PDT Wed Jul 15 2026

.KEY MESSAGES...

- Isolated to scattered thunderstorms will develop mainly across
  the Cascades this afternoon and evening, then across the
  Cascades and eastern mountains on Thursday.

- Low pressure off the coast will move southward through this
  evening, then begin to move northward overnight and on
  Thursday. Models have come into better agreement that the low
  will move around the periphery of high pressure into British
  Columbia.

- A large area of high pressure will build into the region with
  warming temperatures into the weekend and early next week,
  possibly reaching or exceeding 100 degrees in the Columbia
  Basin and nearby locations.

&&

.DISCUSSION...
Southwesterly flow across the area and several short waves
moving through it will keep the chance for showers and isolated
to scattered thunderstorms, mainly over the mountains through
Thursday. Additionally, an area of low pressure off the coast
was heading south and east and will provide enhancement to the
southwesterly flow. This low will begin to move northward
tonight and be in British Columbia Friday morning.

Once the low moves north, the ridge to the east will build in
and any precipitation chances will come to an end through the
weekend.

Temperatures will begin to warm, with highs in the upper 90s to
around 100 degrees (if not higher) as we go into the weekend and
early next week across the Columbia Basin, Yakima Valley and
portions of the Blue Mountain Foothills. These temperatures
would be 15 to 10 degrees above normal. HeatRisk will be
solidly Moderate across much of our area, with a 30 to 50
percent chance of Major HeatRisk early next week across the
Columbia Basin and Yakima Valleys.

By early next week, additional southwest flow will bring
additional shower and thunderstorm chance, mainly to the
mountains.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
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 are forecast to initiate by mid-
afternoon in central Oregon then 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.

&&

.Preliminary Point Temps/PoPs...
PDT  97  62  93  57 /  20  20  20  10
ALW 100  67  97  63 /  10  20  20  10
PSC 101  66  99  62 /  10  20  20  10
YKM  99  67  97  60 /  10  70  40  10
HRI 100  67  96  61 /  20  20  20   0
ELN  96  64  93  57 /   0  70  50  10
RDM  91  55  87  47 /  30  30   0   0
LGD  96  61  97  58 /  20  20  30  20
GCD  94  58  97  55 /  30  20  10  10
DLS  98  65  85  59 /  20  70  20   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.
OR...Heat Advisory until 5 AM PDT Thursday for ORZ041.
     Heat Advisory until 9 PM PDT Thursday for ORZ044-049-050-507.

&&

$$

DISCUSSION...77
AVIATION...86