078
FXUS66 KPDT 141758
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1058 AM PDT Mon Sep 14 2026

.KEY MESSAGES...
- Next chances for rain confined mainly to the mountains mid-
  week, late Tuesday/Tuesday night and late Thursday/Thursday
  night.

- Slight chance (10-20%) of thunderstorms over the Blue
  Mountains region Thursday and Friday.

&&

.DISCUSSION...
Water vapor imagery shows an upper-level low exiting to the
northeast leaving a moist northwesterly flow aloft. Upslope
precipitation will continue to taper off over the Blue Mountains
early this morning, with mostly dry conditions already in place
elsewhere. Recent rainfall coupled with clearing skies and light
wind has resulted in patchy dense fog formation, most notable in
the Yakima Valley. Have issued a Special Weather Statement for
the fog, but given its patchy coverage and intermittent presence
at ASOS locations, have opted to forgo an advisory. Elsewhere,
upslope stratus has induced low visibilities along OR 204 in the
vicinity of the crest of the Blue Mountains.

Below-normal temperatures are forecast today as northwesterly
flow aloft continues. Flow aloft is expected to transition to
southwesterly by Tuesday afternoon and Tuesday night as a
shortwave diving south along the Pacific coast cuts off over the
Pacific Northwest. This low will provide our next chances
(15-40%) of precipitation Tuesday afternoon and Tuesday night
over the mountains, though confidence is just medium (50-60%)
in the track of the low based on clustering of current 00Z
ensemble solutions so anticipating some fluctuations in the PoP
forecast until confidence increases in the track of the low.
Roughly 75% of solutions cut the low off over southwest Oregon
and northwest California, while the remaining take it farther
east over eastern Oregon. A subset of members take the low far
enough offshore of northwest California to keep the forecast
area dry. Ensemble solutions keep the low in place through
Wednesday before taking it inland on Thursday. Quite a bit of
ensemble spread is evident by Thursday afternoon, with roughly
55% of members showing a closed low ejecting northeast over
southern to eastern Oregon. The remaining members show the low
transitioning to a weaker open-wave trough. The former scenario
would result in better chances of convection over the Blue
Mountains and central Oregon, while the latter would be drier.
Currently have a slight chance (10-20%) of thunderstorms for the
Blue Mountains on Thursday. Ensemble solutions remain split
through Friday, though all clusters take the low farther inland.
Chances of precipitation persist in 57% of members, and there is
a low (10-15%) chance of thunderstorms Friday afternoon for the
Blue Mountains should the aforementioned scenario materialize.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Breezy southwesterly-westerly winds continue to linger this
morning at KPDT/KALW; while lighter winds are expected
elsewhere. Stratus cloud cover is expected to remain fairly
decent for VFR flight conditions by the early afernoon hours.
All airports, except KPSC, will see OVC conditions by 18Z (80%
confidence),but will still be in VFR flight conditions for
majority of the afternoon hours. KSPC will see some SCT cloud
cover for majority of the afternoon until the next issuance.

&&

.Preliminary Point Temps/PoPs...
PDT  70  42  67  45 /   0   0   0  10
ALW  70  47  70  48 /   0   0   0  10
PSC  74  45  70  46 /   0   0   0  10
YKM  69  47  66  48 /   0   0  10  10
HRI  73  44  70  46 /   0   0   0  10
ELN  65  42  61  42 /   0   0  20  10
RDM  71  37  70  39 /   0   0   0  20
LGD  69  41  72  45 /   0   0   0  20
GCD  70  41  75  44 /   0   0   0  30
DLS  74  50  72  54 /   0   0   0  10

&&

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

&&

$$

DISCUSSION...86
AVIATION...01