233
FXUS66 KPDT 202246
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
346 PM PDT Mon Jul 20 2026

.KEY MESSAGES...
1. Continued dry and warm conditions through the week
    *Excessive Heat Watch in Effect*

2. Isolated to scattered thunderstorms Wednesday and Thursday

3. Hot, dry and windy conditions return Friday

&&

.DISCUSSION...
Current radar is showing a few echos across the central portion of
the region. Ground observations show mostly a trace with a few
isolated locations in central OR showing 0.02-0.03 inches of rain.
Satellite shows clouds over much of the region with heavy smoke near
the surface. The smoke has kept the temperatures across the region 5-
7 degrees below the original forecast. Temperatures are sitting
in the upper 70s instead of the mid 80s.

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 70-80% 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 ands 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 (70-90%).

By Wednesday, models are in decent 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.
Clusters show the main difference to be mainly with the amplitude of
the ridge. 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 400-500 J/kg, lapse rates
9-10 C/km, effective bulk shear of 25-30 kts and LIs of -4 and PWATs
of 0.05-1.0 inches. NBM QPF continues to show these storms to be
more on the drier side with less than 10% chance of a wetting rain.
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. This pattern is similar to the pattern from
last week and therefore a Red Flag Warning has been issued for
abundant lightning over central OR and the eastern mountains 11 AM
Wednesday to 11 PM Wednesday.

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 /00Z TAFS THROUGH 00Z WEDNESDAY/...
VFR conditions prevail at DLS/RDM/BDN/YKM over the next
24-hours. Lingering smoke from local wildfires poses a chance
for smoke to inhibit any site, especially during sunset,
sunrise, and the general early morning hours. Currently, smoke
is impacting PDT/ALW/PSC with MVFR to IFR conditions, and will
likely linger through the late afternoon/early evening hours
today. We will continue to see smoke impacts at TAF sites
through at least Wednesday. Otherwise, small chance of showers
passing through PSC/ALW/PDT (though not strong enough to clean
out the smoke) over the next few hours as light returns is
advertised across the Colombia Basin.

&&

.FIRE WEATHER...
There are two periods of concern for fire weather.
The first is with the potential for thunderstorms on Wednesday
through central OR and the eastern mountains. There is a 10-30%
chance of isolated to scattered thunderstorms through the
aforementioned portion of the CWA. These thunderstorms are
expected to bring gusty outflow winds of 25-35 mph as well as
abundant lightning. With that, a Red Flag Warning has been
issued for OR zones 698, 700 and 705.

&&

.Preliminary Point Temps/PoPs...
PDT  62  96  66 100 /  10   0   0   0
ALW  67  99  71 102 /  10   0   0   0
PSC  65 100  68 103 /  10   0   0   0
YKM  68  99  70 102 /   0   0   0   0
HRI  66  99  70 103 /  10   0   0   0
ELN  65  97  68  99 /   0   0   0   0
RDM  58  93  62  95 /  10  10  10  30
LGD  62  97  66  99 /   0   0  10   0
GCD  59  95  63  97 /   0   0  10  10
DLS  69 101  73 104 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory from 11 AM Tuesday to 9 PM PDT Thursday for
     WAZ024-027>029.
     Air Quality Alert until 9 AM PDT Wednesday for WAZ028>030.
OR...Heat Advisory from 11 AM Tuesday to 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...82