409
FXUS66 KPDT 291737
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1037 AM PDT Sat Aug 29 2026

.KEY MESSAGES...
- High confidence (99%) that a low-pressure system will track
  over the Pacific Northwest today into early Sunday, resulting
  in below-normal temperatures and widespread breezy westerly
  winds.

- Elevated fire weather conditions today due to breezy winds,
  but low confidence (<40%) in widespread Red Flag conditions.

- Very low to slight chance (5-15%) of thunderstorms today for
  the Washington Cascades and northeast Blue Mountains.

- Low-medium probability (20-50%) of near-freezing morning low
  temperatures in populated, cold-prone valleys of central and
  northeast Oregon on Sunday, except medium-high probability
  (50-75%) in Wallowa Valley.

&&

.DISCUSSION...
Satellite imagery early this morning shows a closed upper-level
low over northwest Washington and southwest British Columbia.
Confidence is very high (99%) that the low will track inland
over the Pacific Northwest today, then exit to the east through
Sunday. Widespread breezy westerly winds are forecast today,
strongest though the Cascade gaps. NBM probabilities suggest
generally medium (30-70%) chances (locally higher) of reaching
advisory-level wind gusts through our most wind-prone areas
such as the Kittitas Valley and the eastern Columbia River Gorge
and vicinity. Despite the breezy winds, chances of widespread
Red Flag conditions are low (<40%) due to below-normal
temperatures and seasonably low relative humidity.

Rain showers are very likely (up to 95% PoPs) along the
Washington Cascade crest this morning into early afternoon as
the low swings inland. Chances of showers and thunderstorms are
lower (5-15%) over the Blue Mountains this afternoon, but still
worth a brief mention.

Looking ahead, there are low-medium chances (20-50%) of near-
freezing morning temperatures (lower to middle 30s) in
populated, cold-prone valleys of central and northeast Oregon
Sunday and Monday in the wake of the cold upper low, except for
50-75% Sunday morning for Wallowa Valley. NBM probabilities are
likely too aggressive Sunday morning due to some lingering
breeziness into the early overnight hours, though forecast PWATs
(generally 0.4" or less) and temperatures aloft are supportive
of chilly conditions. Thinking the coldest temperatures in some
valleys will fall on Monday morning with light winds areawide
under a shortwave ridge, something NBM probabilities do not
highlight well. Did issue a Freeze Watch for Wallowa Valley,
valid later tonight into Sunday morning.

Analysis of ensemble clusters suggests a continued troughing
pattern for the Pacific Northwest by the middle of next week
with all four clusters exhibiting some flavor of trough/upper
closed low and near-normal or below-normal 500-hPa heights.
Will the region see its first widespread wetting rain with the
fall-like pattern? NBM probabilities are quite optimistic for
the 48-hr period ending 5AM Friday. In general, it shows 40-70%
chances of 0.10" of precipitation for non-mountain areas with
50-90% chances across the mountains (highest chances for the
Cascades).

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
VFR conditions through the TAF period with mid to high FEW to
OVC skies associated with a passing weather system. Breezy winds
have developed through most of the sites, with top gusts
reaching 20-30 knots. Strongest winds are currently peaking with
the system moving through the region and I expect winds to
weaken as we go through the late afternoon hours as the system
pushes through. Will see some breezy wind gusts linger through
the Central Oregon sites (BDN/RDM) but not expecting to be
stronger than 20-30 knots for the most part.

&&

.Preliminary Point Temps/PoPs...
PDT  73  43  77  44 /   0   0   0   0
ALW  74  49  77  50 /   0   0   0   0
PSC  78  47  80  48 /   0   0   0   0
YKM  75  49  81  53 /   0   0   0   0
HRI  75  48  81  48 /   0   0   0   0
ELN  68  43  76  46 /  10   0   0   0
RDM  72  35  79  40 /   0   0   0   0
LGD  74  40  79  43 /   0   0   0   0
GCD  76  41  80  46 /   0   0   0   0
DLS  74  52  81  55 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...None.
OR...Air Quality Alert until noon PDT Monday for ORZ041-505-506-
     509>511.
     Freeze Watch from late tonight through Sunday morning for
     ORZ050.

&&

$$

DISCUSSION...86
AVIATION...95