768
FXUS66 KPDT 032349
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
449 PM PDT Thu Apr 3 2025


.Updated Aviation Discussion.


.AVIATION...00Z TAFS...VFR conditions currently at all sites, which
will stay the course through the period. Winds will stay light and
below 10 kts through Friday afternoon, with the only exception being
KDLS which will hover around 10 kts through the remainder of the
evening. Ceilings will stay near 10kft overnight before lifting
through Friday morning and afternoon. 75


&&

.PREV DISCUSSION... /issued 206 PM PDT Thu Apr 3 2025/

SHORT TERM...Tonight through Saturday...Water vapor satellite
imagery this afternoon shows a broad upper trough gradually
pushing east while upper level ridging builds offshore the PacNW.
Visible satellite and radar imagery show light showers continuing
south across the Blue Mountains this afternoon, with partly cloudy
conditions across much of the area and mostly cloudy conditions
across the eastern mountains.

Through this evening, a shortwave slowly sliding down the backside
of the broad upper trough will continue to bring rain/snow shower
chances (20-40%) across the northern Blues and Wallowa county
while the rest of the forecast area remains dry with locally
breezy conditions. By tonight, the upper level trough and
shortwave will push east of the region, allowing the upper level
ridge offshore to begin pushing onshore. Dry conditions and a
warming trend of 2-5 degrees between each day will develop with
the upper ridge overhead through the weekend. Locally breezy to
breezy conditions today will also give way to light winds and
light afternoon gusts as the upper ridge continues to shift east.
While conditions are expected to warm each day, clear skies and a
lingering cold airmass will result in valley areas and portions of
the Columbia Basin to dip to or just below freezing tonight. This
will also result in a chance (25-40%) of frost developing across
portions of central OR, north central OR, and portions of the
Columbia Basin, dropping to 10% or less by Saturday morning as
the warming trend takes hold. Lawhorn/82

LONG TERM...Sunday through Thursday...

1. Dry weather to begin the period

2. Upper level trough to bring precipitation to region with
   lingering mountain showers.

3. Temperatures to flux between above and near seasonable

Models are in relatively firm agreement that an upper level ridge
will situate itself over the region through Sunday afternoon. The
upper level ridge will bring dry and warm conditions across the area
with above seasonal average temperatures. By Sunday night, models
show an upper level trough to begin pushing onshore bringing a
surface cold front, cooler temperatures and high probabilities of
widespread precipitation. Most notable variation in the clusters for
the trough is the timing of the oncoming precipitation. Models show
the trough to meander across the region and exiting Monday night. An
upper level `dirty` 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. Raw ensembles show the 24 hr probability of precipitation
of 0.50 inches to be 70-90% along the Cascade crests and 40-70% for
the higher elevations of the eastern slopes. 30-60% probabilities
for 0.05 inches along the Blue Mountains and the foothills and 50-
70% for central OR. Lastly, 10-20% probabilities of 0.01-0.03 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 isolated thunderstorms embedded
Monday and Tuesday.

Temperatures will fluctuate through the longer term between above and
at normal temperatures. The trough 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 ranges between 5-10 degrees.
Temperatures will be more widespread above normal 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 through Thursday. 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 through
Thursday will return to temperatures much like Saturday and
Sunday. Confidence in the temperature is moderate/high (70-90%)
with raw ensembles in agreement. 90


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  33  60  34  67 /   0   0   0   0
ALW  36  60  36  65 /   0   0   0   0
PSC  34  65  33  69 /   0   0   0   0
YKM  34  63  35  66 /   0   0   0   0
HRI  34  64  33  69 /   0   0   0   0
ELN  32  60  34  64 /   0   0   0   0
RDM  28  60  28  69 /   0   0   0   0
LGD  30  57  29  62 /   0   0   0   0
GCD  27  57  30  63 /  10   0   0   0
DLS  37  66  38  70 /   0   0   0   0

&&

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

$$

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