565
FXUS66 KPDT 182340
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
440 PM PDT Fri Jul 18 2025

.Updated Aviation Discussion...

.AVIATION...00Z TAFS...VFR conditions currently across all sites,
which will stay the course through the period. The main concerns
revolve around elevated winds across all sites due to a passing cold
front. Sustained winds of 12-20 kts with gusts up to 30 kts will be
possible, with highest winds expected at KDLS/KPDT through this
evening. Winds will stay breezy through the period for most sites,
with the exception of KYKM/KPSC. 20-25kft SCT-BKN ceilings will
accompany the cold front this evening, dissipating overnight but
returning at KDLS/KYKM/KALW/KPSC late in the period. 75


&&

.PREV DISCUSSION... /issued 203 PM PDT Fri Jul 18 2025/

DISCUSSION...Tonight through Friday. Key Messages...
 - Critical fire weather conditions this afternoon and evening
   with hot, dry, and windy conditions, except across northeast OR
   and the upper east slopes of the WA Cascades
 - Heightened fire weather conditions Saturday across the Lower
   Basin and Kittitas Valley
 - Slight chance of isolated thunderstorms over the WA Cascades
   and eastern mountains Monday
 - Cooler, near average Sunday into early next week with highs
   rebounding above average Wednesday onward with a drying trend
   late next week.

Latest water vapor imagery shows a shortwave trough descending
into WA with a low over British Columbia in tandem with
increasing mid-level flow spreading into south central WA. Latest
day cloud phase imagery shows largely clear skies outside south
central WA downstream of approaching high clouds. The shortwave
trough will continue dropping southeastward with its attendant
dry cold front crossing the area early tonight. Increasing W-SW
winds ahead of the front will be reinforced with the strongest
winds and gusts expected 5-11 pm today with minimum RH 10-20%
common across the lower elevations. Increased confidence, 80% or
higher, with gusts greater than 25 mph across the Lower Basin,
eastern Columbia Gorge, south central WA; highest gusts spilling
out of the eastern gorge into north central OR and the Kittitas
valley wherein daily peak gusts of 39 mph or more are anticipated
(80-100% chance). Winds will then subside and lessen gradually
overnight.

Despite cooler air mass post-frontal, a favorable overlap of
breezy winds and afternoon humidity is expected again as the
upper low sags to the southern BC-Alberta border. Of which,
elevated to locally critical fire weather conditions are expected
across a portion of the eastern Gorge into northern Sherman,
Gilliam, Morrow counties and Kittitas valley. Highs will drop 4-8
degrees tomorrow from today. Meantime, afternoon RHs will be near
to slightly above seen today across south central WA owing to
modest isentropic descent and drying via 305-310 theta surfaces as
seen among deterministic guidance. Breezy to gusty winds still
expected with modest pressure differences seen cross-Cascades
though flow aloft not as strong as this afternoon and evening.

Quiescent fire weather conditions Sunday-Tuesday with respect to
humidity and winds owing to a relaxed pressure gradient and more
BL moisture. With the upstream amplification of an upper ridge in
the eastern North Pacific and Gulf of Alaska late Saturday-Sunday,
mean mid-level troughing will take hold downstream over the
region Sunday-Tuesday. This with increased moisture and marginal
instability with gudience supporting robust precipitable waters in
place for this time of year will promote low chances, 10-25%, for
thunderstorms Monday across the eastern mountains and WA
Cascades, including chances for wetting rain as high as 30%. This
threat will then shift farther east Tuesday, and be confined to
the far eastern mountains.

Looking onward, ensemble guidance favors a building upper-level
ridge Wednesday-Thursday over the eastern CONUS with weak
troughing/zonal westerly flow over the region. Meantime,
clustering scenarios lean towards a warming and drying trend by
Friday in response to the most likely outcome of a southwest flow
regime taking hold by Friday (~75%). As such, drying and warming
trend is anticipated with highs reading few-several degrees above
average Wednesday-Friday. This scenario could result in elevated
fire weather concerns. Of which, latest hot-dry-windy reflects
this with GEFS showing increasing chance of exceeding the 75th and
90th percentile Wednesday and Thursday across the Lower Columbia
Basin and south central WA.


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  61  88  59  84 /   0   0   0   0
ALW  65  88  62  83 /   0   0   0   0
PSC  60  91  58  86 /   0   0   0   0
YKM  59  88  57  85 /   0   0   0   0
HRI  61  90  60  86 /   0   0   0   0
ELN  57  84  57  83 /   0   0   0   0
RDM  52  85  49  83 /   0   0   0   0
LGD  57  85  56  83 /   0   0   0   0
GCD  56  87  53  85 /   0   0   0   0
DLS  61  84  61  82 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 10 PM PDT this evening for ORZ691-696>698-
     700-701-703.

WA...Red Flag Warning until 10 PM PDT this evening for WAZ690-691.

&&

$$

SHORT TERM...80
LONG TERM....80
AVIATION...75