278
FXUS66 KPDT 022355
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
455 PM PDT Wed Apr 2 2025

.Updated Aviation Discussion.


.AVIATION...00Z TAFS...VFR conditions currently at all sites, which
will stay the course through the period. Breezy west winds with
gusts between 15-25 kts will occur for KDLS/KPDT/KRDM through the
evening before dissipating later tonight. Ceilings will hover
around 10kft and stay BKN overnight and into Thursday morning for
most sites. KDLS/KYKM will be the exception, with ceilings at
25kft and BKN through the period. 75


&&

.PREV DISCUSSION... /issued 216 PM PDT Wed Apr 2 2025/

SHORT TERM...Tonight through Friday...Satellite imagery this
afternoon shows the PacNW on the backside of a broad upper trough
over the western CONUS with partly cloudy conditions in the lower
elevations and mostly cloudy across the mountain zones. While the
lower elevations have remained dry, scattered rain/snow showers
across the mountains have resulted in very light precipitation
being reported.

Light rain/snow showers will continue across the Cascades, eastern
mountains, and Wallowa county today as a shortwave slides down the
backside of the trough and across the PacNW. The shortwave trough
passage combined with cold air aloft (resulting in higher mid/low
level lapse rates) and daytime heating will result in a slight
chance of thunder over eastern Wallowa county this afternoon, as
well as convective rain/snow showers over the rest of the mountain
areas. In the lower elevations, the shortwave passage will result
in breezy conditions through the evening, with strongest winds
(25-35mph gusts) through the eastern Gorge, Kittitas valley, and
other Cascade gap regions. Shower activity will gradually decline
overnight with the lack of daytime heating.

Shower activity will pick up once again early tomorrow afternoon
across the Blues and Wallowa county as the shortwave trough and
parent trough continue to push east.Breezy winds will once again
develop through the Cascade gaps tomorrow afternoon, with winds
becoming locally breezy as they reach the Columbia Basin and
adjacent lower elevations. The upper trough will continue to push
east of the region tomorrow, allowing an upper level ridge to
build into the PacNW late Thursday through Friday. A drier and
more mild airmass will filter into the PacNW with the arrival of
the upper ridge, bringing an end to shower activity area-wide
Thursday night. Dry conditions will persist through Friday and
into the weekend, while a warming trend will result in
temperatures warming into the lower to mid 60s across the lower
elevations Friday afternoon. Lawhorn/82

LONG TERM...Saturday through Wednesday...

1. Dry weather to begin the period

2. Upper level trough to bring precipitation to region

3. Temperatures to flux between above and near seasonable

The long term will be characterized by a ridging pattern to begin
bringing dry and warmer conditions. The next system will approach
the region late Sunday afternoon bringing with it a surface
front, mountain rain and high mountain snow followed by lower
elevation rain Monday. Another upper level ridge will follow soon
after bringing warmer and dry temperatures back to the region
Tuesday and Wednesday.

Models are in relatively firm agreement with an upper level ridge
situated over the region Saturday through Sunday afternoon. The upper
level ridge will bring dry conditions across the region. By Sunday
afternoon, models show an upper level trough to begin pushing onshore.
Most notable variation in the clusters for the trough is the timing.
GFS wants to bring the mountain precipitation in around 11 AM where as
the ECMWF as well as the Canadian bring it in 6-12 hours later. Models
show the trough to meander across the region and exiting Monday night.
An upper level ridge will then begin to build in over the region
bringing drier conditions to the lower elevations with some high
mountain showers.

Much of the precipitation that will come with the upper level trough
will be along the crests of the Cascades and along the eastern
mountains and the Blues. 24 hour raw ensembles show the precipitation
accumulation along the Cascades to be primarily rain except above 6500
ft. 60-80% of the raw ensembles show the 24 hr probability of
precipitation of 0.20 inches to be 60-80% along the Cascade crests and
the higher elevations of the eastern slopes. 50-60% show the same
amount of precipitation totals for the eastern mountains and the Blues.
Moving into central OR and the foothills of the Blues, 30-50% of the
raw ensembles show probabilities for 0.10 inches for central OR and 40-
60% for the foothills of the Blues. Lastly, 30-40% probabilities of
0.05 inches for the Basin and the adjacent valleys. Lingering showers
will continue over the Cascades, eastern mountains, and the Blues
with less than 15% probabilities of embedded isolated
thunderstorms.

Temperatures will fluctuate through the longer term between above and
near normal temperatures. The ridge to start will bring warmer
temperatures across the region with the EFI showing the higher
than normal temperatures being along the eastern slopes of the
Cascades. The difference from climatological normal temperatures
ranges between 5-10 degrees. Above normal temperatures will
become more widespread Sunday as the ridge settles over the
region with 5-10 degrees above normal across the majority of the
region. A surface cold front associated with the upper level
trough will bring with it cooler temperatures Monday and the
difference from climatological is roughly at or just slightly
below normal. The next ridge will then bring temperatures back
above normal again Tuesday and Wednesday. With that said, NBM
shows temperatures to be in the upper 60s to low 70s across
central OR, the Gorge, Basin, foothills and mountain valleys
Saturday and Sunday. Monday NBM shows temperatures to drop into
the upper 50s to low 60s with isolated upper 60s in the Basin.
Tuesday and Wednesday will return to temperatures much like
Saturday and Sunday. Confidence in temperatures is moderate/high
(60-80%) with raw ensembles in agreement. Bennese/90


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  35  55  33  61 /   0  10   0   0
ALW  36  56  36  61 /   0  10   0   0
PSC  36  61  34  65 /   0   0   0   0
YKM  34  60  34  63 /   0   0   0   0
HRI  36  60  34  65 /   0  10   0   0
ELN  35  57  33  61 /   0   0   0   0
RDM  28  52  27  60 /  10  10   0   0
LGD  29  50  28  56 /   0  10   0   0
GCD  27  48  26  57 /  10  10   0   0
DLS  38  60  37  66 /   0   0   0   0

&&

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

$$

SHORT TERM...82
LONG TERM....90
AVIATION...75