866
FXUS66 KPDT 101021
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
321 AM PDT Sun May 10 2026

.KEY MESSAGES...

1. Dry and warm conditions will persist through the week with near
   record temperatures possible

2. Breezy to windy through the gaps today

3. Midweek pattern shift will bring chances mountain showers and
 thunderstorms

&&

.DISCUSSION...
Current satellite shows some upper level clouds lingering over the
area with a few isolated pockets of mid level clouds over the
Kittitas Valley. CLouds are clearing out of central OR leaving them
with mostly clear skies. This will assist with keeping overnight
temperatures a bit warmer in the mid to upper 40s (70-90%
confidence).

Models show the upper level ridge to still be overhead keeping the
area under warm and dry conditions. Temperatures will be 10-15
degrees above seasonal normal increasing to nearly 20-25 degrees
above normal by Tuesday. Highs Sunday and Monday will be in the upper
70s to low 80s with 80-90% of the NBM raw ensembles in agreement.
Tuesday however, ECMWF. GEFS and NBM ensembles all show temperature
to be nearing the 90s with 80-90% probabilities. Looking at in house
data, the mean max temperatures for Pendleton is 70 degrees, Tri-
Cities is 76 degrees, Walla Walla is 71 degrees. These temperatures
are well below the expected temperatures the ensembles are
suggesting and could possibly break a few temperature records.

Models shoe an upper level shortwave will make its way across the
forecast area today showing another day of breezy to windy
conditions through the mountain gaps. 70-80% of the NBM raw
ensembles show Kittitas Valley and the Gorge seeing sustained winds
between 20-30 mph with gusts of 40-45 mph today starting after 2 PM
and persisting through 9 PM. After the front passes, winds will turn
to typical diurnal winds under the ridge.

Tuesday night models show an upper level system beginning to make
its way into the region. Clusters show the variance between the
models to be the timing and positioning of this system. Some models
want to bring the system into the PacNW as a trough, some want to
bring it a bit farther south of the region while others want to
bring it under the region. Regardless of the scenario, each one
leads to the breakdown of the ridge which will in turn lead to
southwest flow aloft ushering in unstable conditions to the region
allowing for the chances of thunderstorms. Looking at the NBM 12
hour probability of thunder, there is a 20-30% probability of
thunderstorms forming over the OR Cascades as well as over the
eastern mountains by Wednesday. Not only are there chances of
thunderstorms, but there is also a 20-40% of mountain showers as
well.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
VFR conditions will persist through the forecast period. Breezy
conditions will occur across all TAF sites after 18-21Z with
sustained winds of 10-20 kts with gusts 20-25 kts and persisting
through 04Z. CIGs will be primarily 25 kft with no VIS issues.

&&

.FIRE WEATHER...
High pressure will persist through midweek with dry and warming
conditions. A shortwave today will bring breezy west to
northwest winds today, with strongest winds through the
mountain gap areas of the Kittitas Valley and the Gorge. A
breakdown in the ridge Tuesday will result in an increasing
instability through central Oregon and the eastern mountains
where 20-30% probabilities of thunderstorms may occur by
Wednesday. This afternoons RHs will be mostly in the teens to
mid 20s, with single digits in central Oregon with these RHs
returning Tuesday afternoon.

&&

.Preliminary Point Temps/PoPs...
PDT  78  46  76  48 /   0   0   0   0
ALW  79  50  77  51 /   0   0   0   0
PSC  84  50  81  51 /   0   0   0   0
YKM  82  47  80  50 /   0   0   0   0
HRI  81  48  79  49 /   0   0   0   0
ELN  74  44  75  46 /   0   0   0   0
RDM  80  38  82  46 /   0   0   0   0
LGD  83  43  78  45 /   0  10   0   0
GCD  89  42  84  47 /   0   0   0   0
DLS  76  48  82  53 /   0   0   0   0

&&

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

&&

$$

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