177
FXUS66 KPDT 062245
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
345 PM PDT Sun Jul 6 2025

Updated Aviation Discussion

.AVIATION...00z TAFs...VFR conditions expected. Sct high clouds
will thin out this evening, leaving light, terrain-driven winds
less than 12 kts across all sites. Evans/74

&&

.PREV DISCUSSION... /issued 141 PM PDT Sun Jul 6 2025/

SHORT TERM...This afternoon through Tuesday...
***FIRE WEATHER WATCH HAS BEEN ISSUED FOR TUESDAY 2 PM THROUGH
 11PM FOR DRY THUNDERSTORMS.***

The start of the short term will be characterized
by dry and hot conditions. An upper level high has parked over the
region bringing with it hot dry air causing temperatures through
Tuesday to begin to reach critical. Models show daytime highs
today to be above 85 degrees across the Basin, central & north
central OR, the Gorge, Kittitas and Yakima Valleys as well as the
other low lying Basins and valleys across the region. Ensembles
are showing 90-100% probabilities (probs) these temperatures will
come to fruition. Monday as the upper level ridge continues
overhead, models show temperatures to increase to above 90 degrees
in the aforementioned areas with over 90% probabilities.
Overnight temperatures will not provide enough of a reprieve as
they will be in the mid to upper 50s in central and north central
and in the low 60s through the Gorge, Valleys and Basins. Models
show Tuesday to be the warmest day of the period with temperatures
reaching between 100-105 through the Basin, adjacent valleys,
Gorge and the foothills of the northern Blues (80-90% probs) with
the remainder of the areas below 4500 feet in the mid to upper 90s
(80-100% probs). Above that, temperatures will be in the low 80s
along the Blues and 70s along the Cascades (80-90% probs).

Models are in firm agreement with an upper level dry cold front
making its way into the PacNW Tuesday afternoon. Ahead of the
disturbance, models also show there to be an increase in
instability and mid-level moisture. CAMs model derived soundings
as well as the NBM and GFS are all showing surface based CAPE
values ranging between 300-500 J/kg along the eastern mountains
and between 400-700 along the southern portion of Deschutes
County. This coupled with the mid- level lapse rates of 9-5-10.2
C/km and LIs of -4, we cannot rule out the possibility of isolated
thunderstorms along these areas Tuesday afternoon. Ensembles show
a 20-25% probability of isolated thunderstorms beginning after 2
PM Tuesday. With the dry air underneath these storms, there is
high probabilities these storms will produce dry lightning.
Therefore, a Fire Weather Watch has been issued for Tuesday 2 PM
through 11 PM.

As the dry cold front passes, surface models are showing a
tightening of the surface gradients along the Cascades. This will
lead to breezy conditions through the Cascade Gaps on Wednesday
with the Gorge seeing sustained winds of near 30 mph and gusts
nearing 40-45 mph with 60-80% probabilities. This will be another
day of concern as the daytime RHs will barely recover from the
days prior.

LONG TERM...Wednesday through Sunday...Models show there to be
some lingering instability and mid-level moisture Wednesday. Model
derived sounding show CAPE values ranging between 100-150 J/kg,
mid-level moisture of 8-9 C/km and LIs of -1. These will be weaker
storms and will likely need a bit of orographic lift to initiate.
With that said, we cannot rule out the possibility of lightning
and ensembles do so around 20% probabilities.

Wednesday and Thursday will also be the `cooler` days during the
period with ensembles showing temperatures dipping nearly 10
degrees from the cold front passage. NBM shows temperatures to be
in the low to mid 90s in the Basin and foothills of the BLues, mid
to upper 80s in central/north central OR and low 80s in the Gorge
with 80-90% probabilities. Thursday will another 5 degrees cooler
across much of the region with 80-90% probabilities of the
majority of the region seeing mid to upper 80s. After Thursday, a
weak upper level ridge will move over the region again bring hot
and dry conditions back to the region.

FIRE WEATHER...A Fire Weather Watch has been issued for dry
thunderstorms Tuesday between 2 PM and 11 PM. An incoming dry cold
front will bring in increasing instability over the southern and
eastern region of the areas elevating the fire weather conditions.
Also, with the dry cold front, an increase in winds will accompany
the passage and with the already dry conditions and poor daytime
RHs, Wednesday will be another day to continue to monitor.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  59  97  64 101 /   0   0   0   0
ALW  63  96  69 100 /   0   0   0   0
PSC  58  97  64 104 /   0   0   0   0
YKM  61  96  64 101 /   0   0   0   0
HRI  59  98  64 104 /   0   0   0   0
ELN  59  95  64  96 /   0   0   0   0
RDM  49  95  55  96 /   0   0   0  10
LGD  55  92  60  97 /   0   0   0   0
GCD  55  95  60  99 /   0   0   0  20
DLS  63  98  66  96 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Fire Weather Watch from Tuesday afternoon through Tuesday
     evening for ORZ700-705.

WA...None.
&&

$$

SHORT TERM...90
LONG TERM....90
AVIATION...74
FIRE WEATHER...90