256
FXUS66 KPDT 301730
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1030 AM PDT Thu Jul 30 2026


.Updated Aviation Discussion.


.KEY MESSAGES...
1. Dry conditions will persist through the week

2. Instability with slight Chances of dry thunderstorms Thursday

3. Breezy to windy conditions and low RHs return Saturday
                 *Fire Weather Watch*

&&

.DISCUSSION...
Current satellite shows clear skies over the region tonight. Ground
observations show some smoke over the region but not enough to
impact visibility. However, air quality is still poor and
advisories have been issued. This will continue to be an issue
through the remainder of the week.

The upper level low off the cost and the ridge sitting in the Four
Corners has the region wedged between the two systems. Southwest
flow aloft continue to usher in dry air and current satellite shows
very dry air at the surface. This will keep the region dry with
humidities remaining in the upper teens to low 20%. Diurnally driven
winds 10-15 mph will also persist through Friday. This will keep
fire weather concerns elevated but not critical through Friday.

A shortwave will make its way across the region allowing for more
instability to return to the region again today. While thunderstorm
chances are very low, instability could cause active behavior around
fires already on the landscape. NAM forecast soundings show MUCAPE
values between 250-500 J/kg, lapse rates of 8.0 C/km, LI of -2 and
bulk shear of 34 knots. This show clearly that the atmosphere is
unstable and cumulus fields will likely build. With this, one can
also not rule out a thunderstorm or two. Confidence in thunderstorms
is low (>10%) while confidence in the instabiity is high (70-90%).
Especially along the southern and eastern mountains of Oregon.

Saturday will be the next day of concern in the period. Models show
the upper level low to begin making its way onshore and ahead of it
is a surface cold front. This will bring elevated winds to the
region on Saturday. NBM raw ensembles show 50-70% probabilities of
wind advisory (>45 mph) criteria being met through the Kittitas
Valley, Simcoe Highlands, the Gorge and the Columbia Basin. The
winds coupled with the continued dry conditions has will elevate the
fire weather concerns for Saturday. Relative humidities will hover
in the upper 20% to low 30% with some ares seeing a high as 35%
(70- 80% confidence). The low RHs and elevated winds could lead
to critical fire weather concerns on Saturday, therefore a fire
weather watch has been issued.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
VFR conditions currently, which is expected to stay the course
through the period. Breezy winds for KDLS through the the day
today with sustained 15-20kts and gusts of 20-25kts. KRDM/KBDN
will also experience breezy winds this afternoon as gusts hover
between 15-20kts. Elsewhere, winds will stay light (<10kts)
under clear skies. 75

&&

.FIRE WEATHER...
Fire weather concerns remain elevated through Friday with low
RHs and diurnally driven winds. Saturday is the next major fire
weather concerns day with incoming winds exceeding advisory
criteria of gusts greater than 45 mph or sustained winds of 30
mph. NBM raw ensembles show a 50-60% probability of occurrence
of winds exceeding criteria. Daytime RHs will remain low in the
upper 20% to low 30%. The winds could override the RHs creating
critical fire weather concerns Saturday. A Fire Weather Watch
has been issued for the Lower Columbia Basin of OR and WA and
for the canyon grasslands of Wallowa County.

&&

.Preliminary Point Temps/PoPs...
PDT  87  55  92  62 /   0   0   0   0
ALW  90  60  95  66 /   0   0   0   0
PSC  92  56  95  62 /   0   0   0   0
YKM  91  57  95  61 /   0   0   0   0
HRI  90  57  94  64 /   0   0   0   0
ELN  86  56  92  59 /   0   0   0   0
RDM  88  47  93  51 /   0   0   0   0
LGD  92  55  98  59 /   0   0   0   0
GCD  94  54 100  57 /   0   0   0   0
DLS  85  58  95  63 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...Fire Weather Watch from Saturday morning through Saturday
     evening for WAZ691-693.
OR...Air Quality Alert until noon PDT Friday for ORZ041-049-050-502-
     503-505-506-509>511.
     Fire Weather Watch from Saturday morning through Saturday
     evening for ORZ691-693.

&&

$$

DISCUSSION...90
AVIATION...75
FIRE WEATHER...90