Grandview, Washington Weather Forecast Discussion

891
FXUS66 KPDT 301750
AFDPDT
Area Forecast Discussion
National Weather Service Pendleton OR
1050 AM PDT Tue Sep 30 2025
.UPDATED AVIATION.
.AVIATION...18Z TAFs...Another round of rain will start tonight,
with showers and an occasional thunderstorm. Widespread rain will
be in the Central OR/Cascade Crest areas, with more scattered and
isolated in the Basin area. Could reach some 5000 feet overcast
decks, with possible sub-VFR decks rolling in areas of the heavier
showers (5-15% chance). Wind will be gustier near Central OR in
RDM/BDN with up to 15-25 knots of gusts when the system starts
pushing through. The highest gusts is forecasted in the later
afternoon/early evening hours today.
&&
.PREV DISCUSSION... /issued 346 AM PDT Tue Sep 30 2025/
DISCUSSION...
Weather conditions across the area are much quieter than yesterday
in the wake of the recent cold front. Minimum RH is still rather
low across portions of central OR, sustaining elevated wildfire
danger, but winds are much lighter today with only a few sites
across the CWA reporting gusts this afternoon. Temperatures are
running a good 15 degrees cooler than 24 hours ago and are
expected to top out in the upper 60s to mid 70s in most areas.
Generally benign conditions are expected this weekend. Dry weather
is anticipated through Sunday afternoon with temperatures climbing
into the mid 70s to lower 80s. A trough will dig over the
northeast Pacific Ocean, remaining off the West Coast through next
week. As this trough approaches, it will kick the stubborn SoCal
low off to the east with strong southwest flow aloft developing
over the PacNW. An increasing pressure gradient across the
southern Cascades will increase southwest winds Sunday afternoon,
but wind speeds are expected to remain in the 10-15 mph range. NBM
probabilities for 15 mph or greater wind speeds are limited to far
southern Deschutes and Crook Counties. This will result in
elevated wildfire danger, but critical thresholds are unlikely to
be met.
Column moisture will increase with precipitable water near the
90th percentile on Monday as the southwest flow aloft advects
Pacific moisture into the region. Occasional rain showers will
develop as early as Sunday evening, with periods of unsettled
weather anticipated Monday through midweek. We`re still a bit too
far out to try and time individual shortwave troughs, but at this
time, the most favorable windows for appreciable precipitation are
Monday evening and Tuesday night into early Wednesday as a cold
front moves across the region.
A wetting rain is likely (>60% chance) pretty much area wide. In
fact, there is a 60% chance of seeing at least 0.25" of rainfall
outside of areas that are typically affected by the rain shadows
associated with southwest flow aloft. This precipitation would
really help to wind down the fire weather season across the
region. There is also a low chance (25% chance) for light snow
accumulations in the higher elevations of the Wallowa Mountains by
midweek as snow levels drop to ~7000 ft. However, any
accumulations will be very light.
There are still significant differences in now the global
ensembles evolve this trough by late week. As was the story
yesterday, the GEFS more heavily favors a deeper trough while the
EPS/GEPS depict a less amplified pattern by Wednesday/Thursday.
The cloud cover/precip and cooler, post-frontal air will result in
maximum temperatures near to slightly below climatology next
week. /MJ
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT  74  52  70  46 /  20  40  40  40
ALW  74  55  70  50 /  30  40  40  50
PSC  74  52  70  46 /  10  40  30  20
YKM  72  47  67  42 /  10  60  30  20
HRI  75  52  71  46 /  10  40  30  30
ELN  68  42  65  39 /  10  70  30  20
RDM  68  42  65  35 /  30  60  40  20
LGD  72  47  68  43 /  40  40  50  50
GCD  71  46  68  42 /  10  40  20  30
DLS  73  52  69  49 /  40  80  60  30
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&
$$
DISCUSSION...MJ
AVIATION...95

NWS PDT Office Area Forecast Discussion