373
FXUS66 KPDT 110430
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
930 PM PDT Sun May 10 2026

.KEY MESSAGES...

- Conditions will remain dry and warm into the midweek

- Breezy conditions today, with strongest winds in the Cascade
  Gaps

- Mountain rain shower and isolated thunderstorm chances return
  midweek

&&

.EVENING UPDATE...issued 422 PM PDT Sun May 10 2026...
Winds have touched advisory criteria through the Kittitas Valley
this afternoon, and am anticipating (80 percent confidence) them
to remain in the 25-35 mph range with gusts up to 45 mph through
evening as a shortwave trough passes over the region and cross-
Cascade pressure gradients remain tight (5-7 mb difference
between SEA and ELN). Thus, have opted to issue a short-duration
Wind Advisory, valid until 8 PM this evening.

&&

.DISCUSSION...issued 251 PM PDT Sun May 10 2026...
Tonight through Monday: Satellite imagery this afternoon shows
a shortwave flattening a ridge over the PacNW, with mostly
cloudy conditions across the forecast area. Breezy winds are
developing through the Cascade gaps and along the Cascade east
slopes, with winds beginning to push further east into the Basin
and adjacent valleys.

The upper ridge will continue to influence the region into
Tuesday, keeping conditions dry and warm across the forecast
area. The shortwave passage today will continue to produce
breezy winds late into this evening, with winds generally
15-25 mph and gusts up to 40 mph. Tomorrow, winds will become
light again with clear skies.

Tuesday through Saturday: Ensemble cluster guidance remains 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
central OR and the eastern mountains will result in an increased
cumulus field across the OR Cascades and eastern mountains, with
a very low chance (<10%) of an isolated shower/thunderstorm.

Tuesday night through Thursday, uncertainty remains around the
evolution of an upper low/trough that will shift inland and
across the PacNW. While there is good agreement that low will
kick inland sometime Wednesday, ensemble members are split on
the track of the trough and timing of its passage overhead.
Solutions range from a track over the PacNW, which would result
in shower chances and isolated thunderstorm chances across our
mountain zones and along foothill locations, while a southern
track would limit showers and thunderstorms to central and
eastern OR. Timing of the trough passage will also impact timing
of showers/thunderstorms across the area, with members split on
having the trough out of the region by Thursday evening, or the
trough still impacting the area through Thursday night.
Forecast confidence in shower/thunderstorm extent is moderate
(45-55%) while timing is low-moderate (30-40%).

Friday into Saturday, ensemble members are in generally good
agreement of upper level troughing developing offshore Friday,
then kicking inland through Saturday, though there is
uncertainty in exact timing this far out. As the next trough
kicks inland, expect another round of mountain rain showers to
develop into the weekend. Lawhorn/82

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
VFR conditions are forecast for all sites over the next 24
hours, with cloud cover ranging from SKC to BKN250. Breezy
winds late this evening will slacken overnight, becoming
diurnally and terrain-driven Monday, predominantly 10 kts or
less with periodic afternoon gusts.

&&

.FIRE WEATHER...issued 251 PM PDT Sun May 10 2026...
High pressure remains over the region with dry and warming
conditions into late Tuesday. Breezy west to northwest winds
will continue to impact the region today, with strongest winds
in the Cascade gaps. There will be increasing unstable
conditions across central OR and the eastern mountains Tuesday.
Min RHs Tuesday will generally be in the teens to mid 20s, with
single digits in Central OR. Isolated to scattered mountain
showers and thunderstorms develop Wednesday into the weekend.

&&

.Preliminary Point Temps/PoPs...
PDT  45  75  47  85 /   0   0   0   0
ALW  49  76  51  88 /   0   0   0   0
PSC  49  80  50  91 /   0   0   0   0
YKM  46  79  49  87 /   0   0   0   0
HRI  47  78  48  88 /   0   0   0   0
ELN  43  74  45  83 /   0   0   0   0
RDM  37  81  44  91 /   0   0   0   0
LGD  42  77  45  91 /  10   0   0   0
GCD  42  83  46  95 /   0   0   0   0
DLS  48  81  52  89 /   0   0   0   0

&&

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

&&

$$

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