993
FXUS66 KPDT 091709
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1009 AM PDT Sat May 9 2026

.KEY MESSAGES...
1. Dry and warm conditions will persist through the week

2. Breezy to windy through the gaps Sunday

3. Pattern shift midweek will bring cooler temperatures and chances
   of mountain showers and thunderstorms

&&

.DISCUSSION...
Current satellite shows some high clouds lingering over central an
north central OR. Otherwise, clear skies everywhere else. Even with
the lack of cloud cover, overnight temperatures will continue to be
5 degrees above seasonal normal with temperatures in the upper 40s
across much of the region with some isolated 30s (80-90% confidence).

Models show the upper level ridge to remain parked over the region.
This will keep the area under dry and warm conditions. Models show
Tuesday will be the warmest day of the period. In house comparison
tools show that temperatures will be upwards of 5 to 10 degrees
above normal increasing to 10-20 degrees above seasonal normal by
Tuesday. Saturday and Sunday HREF shows temperatures to be in the
upper 70s to low 80s with 80-90% of the HREF raw ensembles in
agreement. Moving into Monday, NBM raw ensembles show there to be 80-
90% confidence in temperatures remaining in the upper 70s to low 80s
across the region again. By Tuesday, ECMWF and GFS ensembles as well
as NBM ensembles all show 80-90% probabilities of temperatures in
the mid to upper 80s with isolated locations in central OR and the
Basin seeing u to near 91 degrees. This is 20-25 degrees above
seasonal normal.

An upper level shortwave will make its way across the forecast area
again Sunday with models showing another day of breezy to windy
conditions through the mountain gaps. 60-80% of the NBM raw
ensembles show Kittitas Valley and the Gorge seeing sustained winds
between 20-30 mph with gusts of 40-45 mph Sunday starting after 2 PM
and persisting through 9 PM. After the front passes, winds will turn
to typical diurnal winds under the ridge.

Lastly, a shift in the pattern midweek will lead to chances of
mountain showers and thunderstorms. Models show an upper level
system making its way on shore. Cluster ensembles show there to be a
bit of a timing and positing variance within the models. GFS has the
system coming in as a cutoff low to the south of the region while
the ECMWF and Canadian models have it coming in as a nit of a deeper
trough and over the area. Each scenario will lead to the breakdown
of the ridge and southwest winds aloft that will bring in warm air
advection. This will increase the chances of orographic
precipitation as well as thunderstorms. As of now, models are
showing 20-25% probabilities of thunderstorms over the OR Cascade
Wednesday before shifting to the eastern mountains and into Wallowa
County. NBM raw ensembles also show there is a 20-30% probability of
rain showers as well. Temperatures are also expected to decrease by
nearly 5 to 10 degrees as the system moves overhead. With the
uncertainty of the models and ensembles, confidence in the outcome
is low (20-30%). 90

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...VFR conditions with
light diurnally driven winds (less than 12kts) to prevail
through the period. Lawhorn/82

&&

.FIRE WEATHER...
Continued high pressure over the region has kept the region dry
an warm. These conditions will remain through midweek. Models
show a breakdown in the ridge Tuesday which will lead to
increased instability across the area. Breezy conditions will
return Sunday with Kittitas Valley and the Gorge seeing winds of
20-30 mph and gusts between 40-45 with 60-80% confidence. Tuesday
is expected to be the driest day with widespread RHs in the
teens to low 20s with areas in central OR seeing single digits.

&&

.Preliminary Point Temps/PoPs...
PDT  76  48  78  46 /   0   0   0   0
ALW  76  51  79  50 /   0   0   0   0
PSC  80  50  84  50 /   0   0   0   0
YKM  80  51  83  46 /   0   0   0   0
HRI  80  49  82  48 /   0   0   0   0
ELN  76  48  75  43 /   0   0   0   0
RDM  83  45  81  38 /   0   0   0   0
LGD  76  44  84  43 /   0   0   0   0
GCD  80  43  89  43 /   0   0   0   0
DLS  83  53  77  48 /   0   0   0   0

&&

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

&&

$$

DISCUSSION...90
AVIATION...82
FIRE WEATHER...90