576
FXUS66 KPDT 281737
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1037 AM PDT Wed May 28 2025

Updated Aviation Discussion

.SHORT TERM...Today through Friday...A strong high pressure ridge
continues to persist over the forecast area, with today expected
to be hot with highs in the upper 80s and low 90s across the
lowlands. Temps could potentially be higher, if not for an upper-
level SW wave moving over the forecast area later in the afternoon
into the overnight ours heading into Thursday. Such a set-up is
ripe for isolated showers and thunderstorms across the Cascades
and into the east slopes. And given how dry this ongoing ridge is
expected to make the low-levels, storms outside of the mountains
will likely be dry in nature.

CAMs have been a little more aggressive in depicting activity
flaring up this afternoon as a result of this SW wave, with cells
forming in central Oregon around 1-3 PM and spreading northward.
Some HREF members even have isolated cells spilling out as far out
as the lower Columbia Basin, but expectation is that the east slopes
and Cascades will see the best chances for storms (15-25%) given how
dry the low and mid-levels are across forecast soundings for the
eastern half of the CWA. Should note that even though fuels aren`t
dry enough to warrant fire weather headlines this early in the
season, lightning strikes can still spawn new fires this time of
year, just as they did last weekend. Will highlight the potential
across our fire weather products as a result.

Light showers will form across primarily the WA Cascades and east
slopes during the overnight hours heading into Thursday as the
trough axis sweeps through, before ridging builds back in by Friday.
In between these two systems, however, winds will pick up, gusting
as high as 30 mph through the Basin and Cascade Gaps during the day
Thursday, which will not bode well for any fires should they result
from today`s storms. Warm and dry conditions are then expected to
persist Friday into the weekend as a result of the aforementioned
ridge. Evans/74

.LONG TERM...Saturday through Wednesday...Little change in how
ensembles depict the synoptic pattern through the midweek next week.
Ridging through Saturday will give way to a broad low that is
expected to dig down into the Intermountain West Sunday into Monday,
resulting in showers and isolated mountain thunderstorms during the
day Monday. As the PacNW is enveloped by this system, which
ensembles suggest will be stubborn to move out of the region, cooler
air will prevail, providing a stark shift from the hot and dry
conditions expected on Saturday. Highs in the Basin will generally
waver around the 70s Sunday onward, while other areas struggle to
even reach the 70s.

Ensembles show this system cutting off as it dives into the western
CONUS, hence its mulish nature as mentioned above. This could
potentially plunge the forecast area in wrap-around moisture Tuesday
into Wednesday, supported by the NBM depicting PoPs in the 30-50%
range, which is quite unusual given the time of year. Can`t speak on
QPF this far out with too much confidence, but going by pattern
recognition alone, the eastern mountains and foothills could
potentially see a wetting rain that could delay the start of fire
weather season for at least another week or two, depending on how
long this low sticks around. Evans/74

.AVIATION...18Z TAFs...VFR conditions to prevail through the
period. A system approaching the region will produce isolated to
scattered showers and isolated thunderstorms for sites along the
Cascade east slopes (DLS/RDM/BDN/YKM). Prob30 groups for -TSRA
were kept between 22Z-4Z for sites RDM/BDN, -SHRA between 3Z-8Z
for DLS, and -SHRA between 8Z-12Z for YKM. As the system
progresses westward, shower activity will develop along the Blue
Mountains and upper foothills, with showers coming within vicinity
of sites PDT/ALW overnight. There is a <15% chance that sites
impacted by shower activity could see brief MVFR or less
conditions develop under moderate to heavy rainfall. Otherwise,
outside of shower activity, CIGs of sct-bkn are expected AOA 12kft
AGL through the period. Breezy winds 12-20kts with gusts 20-30kts
will develop around 00Z for site DLS and persist through the end
of the period; sites RDM/BDN will see winds increase to around
12-15kts with gusts up to 25kts between 22Z-04Z with light winds
prevailing otherwise; sites PDT/ALW/PSC will increase to 12-17kts
with gusts 20-30kts after 14Z tomorrow with light winds prevailing
the rest of the period; light winds, 12kts or less, will prevail
at site YKM through the period. Lawhorn/82


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  91  60  80  49 /   0  20  10   0
ALW  89  62  80  52 /   0  20  10   0
PSC  93  60  85  48 /   0  20  10   0
YKM  91  60  81  48 /   0  20  10   0
HRI  93  61  82  49 /   0  20  10   0
ELN  90  58  73  46 /   0  20  10   0
RDM  89  49  76  42 /  20  20   0   0
LGD  88  56  76  47 /   0   0  10   0
GCD  91  55  80  48 /   0  20   0   0
DLS  91  58  76  50 /   0  20  10   0

&&

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

$$

SHORT TERM...74
LONG TERM....74
AVIATION...82