629
FXUS66 KPDT 101201
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
401 AM PST Wed Dec 10 2025

Key Messages...

- Excessive Rainfall remains elevated across the Washington Cascades
with numerous flooding impacts.

- Breezy to Windy conditions lasting through Thursday morning.

- Warmer temperatures expected into next week.


.DISCUSSION...

Current radar shows persistent rainfall to be mainly over the WA
Cascades with some spill over in portions of Yakima Counties as well
as the Northern Blues. Winds are gradually settling overnight with
gusts of 20-30 mph for majority of the forecast area. However,
surface observations continue to show localized southwest to west
gusts up to 45-50 mph in small portions of the Lower Columbia Basin
of WA and Cascade gaps along the frontal boundary.

Today through Thursday...Models show a persistently strong
atmospheric river (IVT above 500 kg m/s) along the WA/OR Cascades
with some spills across eastern mountains (Northwest Blues and
Wallowas) through Thursday. This AR will bring QPF amounts in these
areas up to 1-3 inches with higher amounts along the crests of the
western slopes of WA Cascades. 3-hr QPF raw ensembles (HREF) show
the crests to the western slopes of Ellensburg and Yakima up to 1
inch (50-70% probability) and eastern mountains through the Grande
Ronde Valley and Wallowas seeing up to 0.50 inch or more of
precipitation today (<30% prob). With this significant amount of
moisture transport, the flash flood guidance will remain at least
15% along the crest of the WA Cascades. However, eastern mountains
and the Grande Ronde Valley may reach to 0.50 inches or below as the
AR slowly weakens (40-60% confidence). Otherwise, the lowlands will
see dry conditions during the 48-hr period.Many rivers are expected
to reach/exceed bankfull through tomorrow with Naches at Naches,
Yakima at Horlick and Easton exceeding action stage and into minor.
Flood Warnings will remain for those locations until early Saturday
evening hours. All other rivers in the area are still at or nearing
action stage and will be closely monitored as the event continues.

Breezy to windy conditions will prevail through early Thursday
morning. Sustained winds are expected to be at 20-30 mph with
gusts of 45-55 mph across the Columbia Basin of WA/OR along with
Simcoe Highlands, Yakima Valley and portions of the upper slopes
of WA Cascades. CAMS raw ensembles from HREF favor gusts up to
55-60 mph through majority of today over western slopes of WA
Cascades and 45-55 mph for the Foothills Blue Mountains-WA
including Lower Columbia Basin of WA (>60% confidence). That
said, wind advisories will remain through 7 AM PST Thursday for
those aforementioned areas. Confidence increases with the EFI
showing a very unusual climatologically event in the wind
forecast.

Temperatures will continue in a warming trend in the 50s and 60s
into next week. As cloud coverage prevails from the AR, this will
also keep the low temps relatively warm in the 40s and 50 around the
Columbia Basin, but mainly high 30s and low 40s elsewhere.
Feaster/97

&&


.AVIATION...12Z TAFs...Winds will be the prevailing concern through
the forecast period. Winds across all TAF sites are elevated or will
become elevated later in the period. Currently PDT/BDN/ALW are
seeing sustained winds of 11-18kts with gusts to near 25kts. Between
17-21Z the remaining sites will see winds increase and all sites
will see winds between 15-25 kts with gusts nearing 30 kts.

VIS is 2SM (DLS) and 4SM at (YKM) due to BR and low CIGs of 800-
1500ft. This should clear once the winds increase between 17-21Z
respectively. However, confidence in the timing of when VSBY and
CIGs will clear is low/moderate (30-50%). Elsewhere VFR conditions
will persist. An airport weather warning has been issued for PSC due
to to winds gusts of 40-50 kts expected (80-90%). This will continue
through 6 AM Thursday morning. 90

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  64  50  61  44 /  20   0  10  10
ALW  64  54  60  48 /  40  10  30  30
PSC  65  54  63  44 /  10  10  10  10
YKM  62  47  60  41 /  40  30  20  10
HRI  65  53  63  44 /  10  10  10  10
ELN  58  43  52  39 /  70  40  20  30
RDM  63  36  60  31 /  10   0   0   0
LGD  58  45  55  41 /  20   0  20  20
GCD  58  39  56  36 /   0   0   0   0
DLS  63  54  61  47 /  50  60  30  30

&&

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

WA...Wind Advisory until 7 AM PST Thursday for WAZ024-027>029-521.

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

&&

$$

DISCUSSION...97
AVIATION...90