944
FXUS66 KPDT 212142
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
242 PM PDT Tue Jul 21 2026

.KEY MESSAGES...

1. Continued dry and warm conditions through the week
      *Heat Advisory in effect*

2. Isolated to scattered thunderstorms Wednesday and Thursday
      *Red Flag Warning Wednesday For Abundant Lightning*

3. Hot, dry and windy conditions return Friday

&&

.DISCUSSION...
Current radar is showing a few echos across the central portion of
the region. Satellite shows some mid level cloud cover over the same
area as the mid level moisture begins to build into the region. So
far no ground observations are showing any precipitation with the
cells that are moving across. Enough of the smoke has cleared that
temperatures were able to climb this afternoon with the current
temperatures around the region being in the low to mid 90s with high
70s and 80s along the ridgelines.

Models show the upper level ridge to remain overhead through
Thursday keeping the region under dry and warm conditions.
Temperatures will steadily increase and there is 80% chance of
seeing major HeatRisk Tuesday through Thursday with highest
probabilities being Wednesday. If the smoke lifts, NBM shows
temperatures to reach between 100-105 in the Columbia Basin and the
Gorge with isolated areas along the foothills seeing upper 90s to
100 degrees. That coupled with the high overnight temperatures in
the upper 60s to low 70s will cause heat related impacts to occur.
Confidence in the HeatRisk is high (80-90%).

By Wednesday, models are in firm agreement and show a slight pattern
shift with the upper level ridge shifting towards the Four Corners
and advecting some monsoonal moisture up into the region.  NBM raw
ensembles show Wednesday to have 40% chance of thunderstorms through
Deschutes and Grant counties after 2 PM. Looking at soundings show
CAPE values over 800 J/kg, lapse rates 9-10 C/km, effective bulk
shear of 30 kts and LIs of -4 and PWATs of 0.05-1.0 inches. Cannot
rule out isolated dry thunderstorms mixed with wet thunderstorms and
with the fuels as ready as they are, not a lot is needed to ignite a
fire, especially if there are strikes outside of the wet core.
Thursday the NBM raw ensembles shows a 30% chance of thunderstorms
creeping up along the WA Cascades as well as out over the eastern
mountains. Forecast soundings show CAPE values in the 500 J/kg range
with -3 LI, 7 C/km lapse rates, we could see some shallow
thunderstorms ignite. Again, fuels in these areas are very
receptive.

Thursday models show a dry upper level low beginning to push into
the region shifting the upper level high of to the east. In house
calculations show the pressure gradients along the Cascades
tightening which will bring elevated winds to the Cascade Gaps as
well as portions of the southern Blues and central OR. NBM raw
ensembles shows the region with the highest probabilities for 20 mph
sustained winds is through the Gorge and foothills of the southern
Blues at 70-90%. 15 mph sustained winds expected through the
Kittitas Valley and through portions of central OR with 60-80%
probabilities. With the continued dry and warm conditions, relative
humidities will remain low and coupled with the winds elevated fire
weather concerns for Friday and Saturday.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Surrounding smoke and haze from local wildfires will bring VFR
to MVFR conditions across many TAF sites through the area. Smoke
will linger for several hours, reducing visibilities. Some
atmospheric mixing during the peak heating hours could bring
back VFR conditions before reducing visibility around sunset.
Winds in general will be light and diurnally driven during the
forecast period.

&&

.FIRE WEATHER...
Isolated to scattered thunderstorms expected Wednesday through
central OR and the southern Blue mountains with 20-40%. There
will be a mix of wet and dry thunderstorms and any strikes
outside of a wet storm core still has the potential to ignite a
fire. These storms are also high based in nature and plenty of
virga will be visible and the potential for gusty outflow winds
of 25-35 mph is likely.

&&

.Preliminary Point Temps/PoPs...
PDT  65  98  67  96 /   0   0   0  10
ALW  70 100  71  99 /   0   0   0  10
PSC  68 102  70 101 /   0   0   0   0
YKM  70 102  72 100 /   0   0  20  10
HRI  69 102  71  99 /   0   0   0  10
ELN  68 100  70  96 /   0  10  20  10
RDM  63  96  59  93 /  10  40  50   0
LGD  65  98  66  99 /   0   0  10  40
GCD  63  97  62  98 /  20  10  20  20
DLS  73 103  71  91 /   0   0  20  10

&&

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

&&

$$

DISCUSSION...90
AVIATION...95
FIRE WEATHER...90