130
FXUS66 KPDT 100525
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1025 PM PDT Sat May 9 2026

.KEY MESSAGES...

- Dry conditions will remain dry and warm into the midweek

- Another round of breezy conditions will develop Sunday,
  strongest winds in the Cascade Gaps

- Mountain rain shower and isolated thunderstorm chances return
  midweek

&&

.DISCUSSION...
Tonight through Monday: Upper level ridging has redeveloped over
the region, with satellite showing cirrus spilling into the
northern half of the forecast area this afternoon. Winds have
been light, with dry conditions across much of the area.

The upper ridge will keep conditions fairly dry while
temperatures remain around 5 to 15 degrees above normal across
the much of the region. These conditions will continue through
Monday as the upper ridge continues to influence the region.
While winds will be light the remainder of today and Monday, a
shortwave passing through the ridge on Sunday will bring another
round of widespread breezy conditions (15-25 mph with gusts
25-40 mph). Once again there is growing concern of stronger
winds through the Kittitas valley, however confidence is only
moderate (55-65%) in wind gusts reaching 45 mph Sunday
afternoon.

Tuesday through Friday: Ensemble cluster guidance is in good
agreement in the breakdown of upper level ridging over the
region Tuesday, with a deeper south to southwest flow developing
as well as a signal for thermal troughing to develop into
eastern and central OR. This will promote a modest increase in
high temperatures over the region, with upper 80s to mid 90s in
the lower elevations, and mid 70s to mid 80s in mountain
valleys. In addition to warming temperatures, instability across
the mountainous terrain will also introduce a slight chance
(15-25%) of showers and isolated thunderstorms for Tuesday
afternoon into the evening.

Tuesday night through Friday, disagreement grows amongst
ensemble guidance in the evolution of the synoptic pattern.
The majority consensus (~60 to 70% of members) is that an upper
low/trough offshore will kick inland sometime late Tuesday into
Wednesday. A northern track of the low feature will bring shower
and isolated thunderstorm chances to most mountain areas and
the Blue Mountain foothills, while a southern track keeps the
best chances across central and eastern OR. Following the trough
passage, a quick transient ridge will bring dry conditions
across the area Wednesday night into Thursday morning
(confidence 45-60%). Thursday afternoon into Friday, ensemble
cluster guidance depicts upper level troughing developing
offshore, with 50% of members favoring shower chances across the
Cascades and eastern mountains, and the other 50% favoring
shower chances only along the Cascade crest. Overall forecast
confidence in timing and extent of shower chances is low-
moderate (25-40%) during the Wednesday through Friday period.
Lawhorn/82

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
VFR conditions are forecast through the period for all sites.
Mostly variable or terrain-driven winds are forecast overnight,
followed by a ramp of westerly winds late morning through
evening as a weather system crosses the region. Mid- to high-
level cloud will persist through much of the period.

&&

.FIRE WEATHER...
High pressure will remain over the region with dry and warming
conditions persisting at the surface. Breezy west to northwest
winds will develop Sunday, with strongest winds through the
Cascade gaps. A breakdown in high pressure Tuesday will result
in an increasing unstable airmass over portions of central
Oregon and the eastern mountains. Afternoon relative humidities
will be mostly in the teens to mid 20s, with single digits in
central Oregon this afternoon and again Tuesday afternoon.

&&

.Preliminary Point Temps/PoPs...
PDT  48  78  46  76 /   0   0   0   0
ALW  51  79  50  77 /   0   0   0   0
PSC  50  84  50  81 /   0   0   0   0
YKM  51  82  47  80 /   0   0   0   0
HRI  49  81  48  79 /   0   0   0   0
ELN  48  74  44  75 /   0   0   0   0
RDM  45  80  38  82 /   0   0   0   0
LGD  44  83  43  78 /   0   0  10   0
GCD  43  89  42  84 /   0   0   0   0
DLS  53  76  48  82 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...None.
OR...None.

&&

$$

DISCUSSION...82
AVIATION...86
FIRE WEATHER...82