Hermiston, Oregon 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

740
FXUS66 KPDT 272327
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
427 PM PDT Fri Jun 27 2025

.Updated for Aviation...


SHORT TERM...Tonight through Sunday...Satellite imagery this
early afternoon shows cumulus fields developing across portions of
northeast OR and southeast WA as an upper trough axis passes over
the region. Otherwise, surface observations indicate breezy
conditions across the lower elevations.

A broad, shallow upper trough will continue to sit over the PacNW
today with shower activity confined to the WA Cascade crest
through this evening. Breezy winds will also continue through the
Cascade gaps into the Columbia Basin today. Tomorrow the upper
trough will be pushed east as upper level ridging builds offshore.
Breezy winds will continue through the Cascade gaps for Saturday,
otherwise conditions will remain dry with locally breezy winds in
the Columbia Basin. Upper level ridging will move inland and
strengthen over the region Sunday, resulting in afternoon
temperatures in the lower to mid 90s developing in the lower
elevations and mid 70s to 80s in the mountains. Lawhorn/82

LONG TERM...Monday through Friday...Ensemble guidance in good
agreement that upper level ridging will persist across the PacNW
through Tuesday morning, before slowly moving east of the northern
Rockies. During this time, afternoon temperatures will continue to
warm across the region, with high confidence (80-90%) of
widespread mid to upper 90s developing both Monday and Tuesday
leading to widespread moderate and pockets of Major HeatRisk
developing; confidence is mod-high (60-80%) in temperatures
reaching or just exceeding the 100 degree mark in portions of the
Columbia and John Day Basins, leading to areas of Major HeatRisk
in these areas. Will continue to monitor for the need of heat
highlights for Monday and Tuesday. Otherwise, as the upper ridge
pushes east on Tuesday, the cross-Cascade surface pressure
gradient will strengthen, resulting in breezy winds returning
through the Cascade gaps and into portions of the Columbia Basin.

Ensemble guidance is also in good agreement that a broad upper low
that develops off the CA coast will help facilitate a monsoonal
moisture push into OR both Monday and Tuesday. Combined with
increasing surface instability and modest mid level Theta-E lapse
rates, slight chances (10-25%) of thunderstorms will develop
across central OR and the eastern OR mountains in the afternoons
and evenings.

Wednesday through Friday, ensemble cluster solutions are in
agreement of upper level troughing developing across the PacNW,
though differences increase in its position and strength. That
said, ensemble cluster solutions favor another round of a slight
chance (~15%) of thunderstorms across the eastern mountains
Wednesday afternoon with dry conditions Thursday into Friday.
While confidence is moderate (60-70%) that temperatures will cool
across the region, there is higher uncertainty in how cool it will
get owing to the disagreement on the strength of the upper trough.
At this time, the NBM deterministic forecast is forecasting high
temperatures in the mid 80s to mid 90s across the lower elevations
and 70s to mid 80s mountains each day (confidence 25-40%).
Otherwise, mod-high confidence (60-80%) that breezy winds will
continue through the Cascade gaps through the end of next week.
Lawhorn/82

AVIATION...
00Z TAFS VFR conditions are expected through the TAF period.
Wind gusts generally in the 15 to 25 kt range, with 30 kts at DLS
will decrease this evening. Winds will then generally be 10 kts or
less. Winds will gust to around 20 kts at DLS, PDT, RDM and BDN on
Saturday afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  55  85  56  92 /   0   0   0   0
ALW  59  83  60  90 /   0   0   0   0
PSC  57  87  57  93 /   0   0   0   0
YKM  53  86  56  91 /   0   0   0   0
HRI  56  87  56  94 /   0   0   0   0
ELN  53  81  55  91 /   0   0   0   0
RDM  45  83  46  90 /   0   0   0   0
LGD  50  79  52  87 /   0   0   0   0
GCD  49  82  50  91 /   0   0   0   0
DLS  57  84  58  93 /   0   0   0   0

&&

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

$$

SHORT TERM...82
LONG TERM....82
AVIATION...77