477
FXUS66 KPDT 100604
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1004 PM PST Tue Dec 9 2025

.AVIATION...06Z TAFs...Steady rain has largely pushed north of the
WA/OR border this evening as a warm front continues to lift north
into Washington. Some light rain at YKM/PSC/ALW is expected (80
percent confidence) to continue into the overnight hours, with
lower confidence (30-50 percent) at DLS/PDT. Periods of sub-VFR
CIGs/VSBYs in FG/BR and/or light rain are forecast into the
overnight hours at all sites except RDM/BDN. Southwesterly to
westerly winds will increase in magnitude at all sites Wednesday
morning through afternoon. For sites where winds remain relatively
light (around 10 kts or less), low-level wind shear (WS) is
forecast as southwesterly winds aloft ramp overnight.

&&

.PREV DISCUSSION... /issued 314 PM PST Tue Dec 9 2025/

AVIATION...00z TAFs...Variable conditions will materialize this
evening as another round of rain showers develop over primarily
the Basin and adjacent valleys. MVFR conditions are possible
(40-50% chance) under rain showers. BDN and RDM are largely
expected to be spared of rain through the period, outside of trace
amounts. Once rain tapers off by around midnight, winds will start
to pick up by sunrise Wednesday. Gusts could reach 30 kts at many
sites, possibly as high as 40 kts in sites across the Basin
(30-40% chance). Cigs will transition from low to mid bkn-ovc this
evening to sct-bkn mid cigs during the day tomorrow. 74

PREV DISCUSSION... /issued 242 PM PST Tue Dec 9 2025/

Key Messages...

- Excessive Rainfall in the elevated category across the
  Washington Cascades with numerous flooding impacts continuing .

- Breezy to Windy conditions beginning overnight and lasting
  though Thursday.

- Warmer than normal temperatures are expected in the extended
  periods.


DISCUSSION...

The synoptic setup shows a trough of low pressure lifting into BC
as a warm front spreads north across WA/OR Today. An Atmospheric
River will remain relevant to the sensible weather Tonight,
lifting northward and spreading more rain along the frontal
boundary. As the AR weakens Tonight and Wednesday, precipitation
will become more relegated to the Cascade Caps and eastern
Mountains, continuing to aggravate the recent onset of flooding
across the Yakima Valley.

Additional river flooding risk will continue along rivers of the
Yakima Valley Tonight as excessive rainfall across the Washington
Cascades remains in the elevated category. This is due to a
combination of runoff from rains along the lower slopes of 1 to 2
inches and several inches from the Upper Slopes.

Breezy to windy conditions are anticipated across the entire area
as a warm front lifts across the area Tonight. The potential for
sustained winds greater than 30 mph ramps up to around 60-80
percent by the overnight hours. This will bring the need for wind
advisories focused largely on the lower Columbia Basin of WA, the
Simcoe Highlands as well as the Foothills of the Northern Blues.
The advisory has been issued for these areas beginning 6 am
Wednesday and lasting through 9 am Thursday.

Temperatures with the westerly flow will be markedly warmer in
the lowlands of the Columbia Basin and central Oregon/John Day
Basin, and typically well into the 60s Wednesday and into
Thursday.

The AR weakens with midweek, however enough moisture transport
appears available to maintain and slight risk (15% chance of
exceeding flash flood guidance) west of a line from Wenatchee to
Hood River through the day on Wednesday. Risk ramps down on
Thursday, but a 5% chance for these conditions persist for the
Upper Slopes. An areal flood watch is in place for much of
Kittitas, Yakima and Klickitat counties through Friday morning.
Russell/71

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  46  64  51  61 /  90  20  10  20
ALW  47  64  53  60 / 100  40  20  40
PSC  46  65  54  63 / 100  10  10  20
YKM  41  62  48  59 / 100  40  50  40
HRI  46  65  53  62 /  90  10  10  20
ELN  37  58  43  52 / 100  70  60  60
RDM  44  63  36  59 /  50  10   0  10
LGD  41  58  46  56 / 100  20  10  30
GCD  45  58  39  56 /  80   0   0  10
DLS  47  63  53  61 / 100  50  70  60

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 6 AM Wednesday to 7 AM PST Thursday for
     ORZ041-044-507-508-510.

WA...Wind Advisory from 6 AM Wednesday to 7 AM PST Thursday for
     WAZ024-027>029-521.

     Flood Watch through Friday morning for WAZ026-027-521>523.

&&

$$

DISCUSSION...71
AVIATION...86