from: NWS Pendleton, OR

416
FXUS66 KPDT 191004
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
304 AM PDT Mon May 19 2025

.SHORT TERM...Today through Wednesday...Gusty winds have finally
calmed down early this morning, however this respite will give way
to a quick-moving upper-level wave embedded within a amplified flow
pattern aloft. This wave will bring a chance of showers to most of
the forecast area, as well as a slight chance of isolated
thunderstorms across the eastern mountains of Oregon. Another round
of breezy winds will also accompany this wave. A more benign zonal
flow pattern then settles in through the midweek, however light
persistent PoPs will prevail over the high mountains as this pattern
favors at least a low-end chance for orographic showers to develop
over the Cascade crests and eastern mountains.

Overnight satellite imagery shows mostly clear skies early this
morning, however that will give way to the aforementioned upper-
level wave, seen on satellite as a shield of mid-level clouds. The
velocity of this system suggests relatively low QPF for at least the
lowlands, but given how this wave is accompanied by amplified NW
flow aloft, orographic enhancement could bring QPF amounts higher
over the mountains with a few tenths of an inch possible (NBM
probabilistic suggests a 50-60% for at least a quarter of an inch of
liquid precip). Winds will generally gust in the 20-25 mph range for
most of the Basin and central Oregon, with gusts closer to 30 mph
for the Cascade Gaps and east slopes of the Cascades, including the
Simcoe Highlands. Thunder chances for the eastern mountains are low-
end (15-25%), but models do pick up on some low-end CAPE in the 200-
400 J/kg range, so did leave some mention of isolated storms for the
area.

Tuesday and Wednesday will be quieter as temperatures warm slightly
under zonal flow. Such a pattern will induce at least slight chance
PoPs for the high mountains, but should note that models are
trending towards making this pattern a bit more amplified than what
was previously expected. More specifically, the deterministic GFS
and ECMWF now hint at a shortwave potentially moving in late
Wednesday into Thursday, which could provide for another quick-
hitting shower and thunderstorm day, along with breezy winds, much
like we`re expecting today. Evans/74

.LONG TERM...Thursday through Monday...Ensembles have a fair handle
on the synoptic pattern through next weekend, however the
progressive nature of the pattern makes it more difficult to key in
on specific features. Both the deterministic GFS and ECMWF suggest a
series of waves on Thursday and Friday, with a stronger trough on
Friday, before high pressure builds in over the weekend. As
mentioned in the short term discussion, impacts with Thursday`s
system are expected to be minor, as the shortwave looks to be weak
and fast, however the trough on Friday does exhibit a bit more of a
negative tilt, which would provide for a higher confidence in storm
chances, especially over the eastern mountains. That being said,
moisture doesn`t look to impressive this far out, so PoPs are low at
this time (20-40%), but that could increase once CAMs are able to
get a handle on how this system evolves.

Temperatures warm over the weekend with ridging over the PacNW, with
highs expected to climb back into the 80s across the lowlands.
Confidence is shaky for Monday, however guidance does appear to lean
toward another trough moving in, inducing SW flow and thus yet
another chance for showers and mountain thunderstorms. Can only
speak with low to moderate confidence, however (30-40%), as some
ensemble members keep ridging in place, suggesting that warm and dry
conditions may persist beyond next weekend. Evans/74

&&

.AVIATION...12z TAFs...A quick-moving weather system will bring a
chance of showers across all sites, with RDM/BDN seeing only slight
chances (reflected by PROB30 in the TAF). All other sites will see
at least a 50% chance of showers between 16 and 22z, with conditions
potentially dropping to MVFR under heavier showers. Dry conditions
will then prevail this evening into Tuesday. Cigs will start bkn-ovc
around 10 kft for most sites, potentially dropping to as low as 3
kft under showers, before clearing and becoming few-sct at around 5-
10 kft at night. Evans/74

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  65  42  64  41 /  90  30  10   0
ALW  65  45  64  44 /  90  50  20   0
PSC  71  45  69  42 /  80  20   0   0
YKM  69  41  68  38 /  70  10   0   0
HRI  70  45  69  43 /  80  10   0   0
ELN  63  39  62  40 /  80  20   0   0
RDM  64  35  62  31 /  40   0   0   0
LGD  58  41  58  35 /  90  70  20   0
GCD  63  38  61  34 /  80  40  10   0
DLS  67  47  66  43 /  70  10   0   0

&&

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

$$

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

NWS PDT Office Area Forecast Discussion