823
FXUS66 KPDT 150526
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1026 PM PDT Wed May 14 2025



UPDATED AVIATION...06Z TAFs...Winds remain breezy at DLS/PDT/RDM.
Winds will decrease heading into the overnight hours and will
slightly increase as a weather system gets closer into the later
part of Thursday. Highest chance of precip is towards the last few
hours and currently only DLS/BDN/RDM have a PROB30 of
precipitation. BDN/RDM have a MVFR visibility of 4SM included in
their PROB30 but no other site is currently expected to drop to
MVFR conditions at this time.

PREV DISCUSSION... /issued 247 PM PDT Wed May 14 2025/

SHORT TERM...Today through Thursday...Low clouds passing across
the mountain areas with some clear skies over the lowlands,
observed from current satellite and radar imagery.

The leading edge of the upper ridge gradually builds over the PacNW
with the trough continuing eastward from the forecast area. Showers
may linger across the Blues, eastern mountains, and WA/OR Cascades
this afternoon before dry conditions return this evening into night.
The raw ensembles favor a 50-90% probability for light QPF amounts
(<0.10 inches) over the mountain areas for today. Sustained winds at
20-30 mph with gusts of 30-40 mph will remain over the Cascade Gaps
through tonight. And due to the marine stratus layer and tight
surface pressure including temperature gradients, this resulted in
warranting a Wind Advisory for Kittitas Valley having northwest
winds exceeding to 35 mph with gusts of 40-50 mph through this
evening. Later tonight, wind conditions should steadily decrease to
breezy (15-25 mph).

Wet conditions will return tomorrow late morning at first the
Cascades before spreading to the remaining forecast area into
Friday. The Northern Blues may receive QPF amounts up to 0.20 inches
with the remaining forecast area at 0.10 inches or less. Breezy
conditions will persist tomorrow into Friday evening around the
Cascade Gaps as well. But, winds should start gradually decreasing
Friday night to light. Feaster/97

LONG TERM...Saturday through Tuesday...Little change in the
overall forecast message from the previous forecast package/shift.
Sensible weather concerns are still anticipated to revolve around
the passage of what ensemble NWP is advertising as either an upper
trough or closed low Saturday through Sunday night. This system will
facilitate widespread showers, breezy winds, and isolated
thunderstorm chances Saturday with precipitation chances tapering
off through Sunday night as the trough moves southeast.

The NBM continues to advertise persistent breezy to windy conditions
through the forecast period, with probabilities of exceeding
advisory-level wind gusts (45 mph) greatest on Sunday; current
probabilities are highest for the Kittitas Valley (60-90%) with
medium-high chances (40-70%) through the eastern Columbia River
Gorge and across wind-prone portions of the Blue Mountain foothills,
north-central Oregon, and the lower Columbia Basin.

The main item worth noting from the ECMWF EFI is the potential for
nearly area-wide atypical winds relative to climatology on Sunday,
especially through the Cascade gaps, evidenced by EFI values of 0.5-
0.9. Additionally, ensemble agreement in a precipitation event for
the eastern mountains is growing with EFI values of 0.5-
0.7 Saturday.

While ensemble-mean 500-mb height and vorticity fields are in good
agreement about the general 500-mb height pattern Monday and
Tuesday, placing a trough downstream over the Great Plains with
quasi-zonal flow over much of the West and a weak shortwave trough
over the northern Pacific Northwest, analysis of ensemble clusters
teases out two different scenarios; one scenario takes the shortwave
farther south over the Pacific Northwest, while the other keeps
quasi-zonal flow or weak ridging over the region. The main driver of
uncertainty is the location/magnitude of the aforementioned
shortwave trough as it moves onshore into British Columbia or
northern Washington. The track that favors precipitation and windier
conditions for our forecast area is evident in roughly 25% of
ensemble members. Plunkett/86

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  41  66  45  66 /   0   0  40  30
ALW  44  66  47  65 /  10   0  40  40
PSC  44  70  46  71 /   0   0  30  10
YKM  42  69  45  70 /   0  10  20   0
HRI  43  69  45  70 /   0   0  30  10
ELN  41  63  43  66 /   0  10  20  10
RDM  33  63  37  67 /   0  10  50   0
LGD  38  63  43  59 /  10   0  50  40
GCD  34  64  41  61 /  10   0  60  20
DLS  45  63  45  68 /   0  20  30   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Wind Advisory until 11 PM PDT this evening for WAZ026.

&&

$$

SHORT TERM...97
LONG TERM....86
AVIATION...95