556
FXUS66 KPDT 021749
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
949 AM PST Tue Dec 2 2025

Updated Aviation Discussion

.AVIATION...18Z TAFs...Variable conditions will prevail through
the period. VFR conditions have developed at sites DLS/PDT/RDM/BDN
this late morning, and are expected to continue through the
afternoon. VFR conditions are anticipated to develop at site YKM,
though confidence is low (20-40%) in timing of vsby improvement.
Sites ALW/PSC will see brief improvement to IFR/MVFR, but vsby and
cigs will deteriorate back to IFR or lower conditions after 5Z.
Sites DLS/PDT/YKM will see MVFR cigs/vsby begin to develop around
or after 4Z and persist into tomorrow morning (confidence 30-50%).
Winds will remain light, 12kts or less. Lawhorn/82


&&

.PREV DISCUSSION... /issued 351 AM PST Tue Dec 2 2025/

.DISCUSSION...A shortwave trough embedded within northwesterly
flow aloft will cross overhead early this morning through the day,
then exit to the south and east through Wednesday morning. Deep
northwesterly flow is facilitating orographic precipitation over
the northern Blue Mountains and other favored areas of northeast
Oregon and southeast Washington. Snow chances are low across the
Blue Mountain foothills and eastern half of the Columbia Basin
(10-25 percent chance of measurable snow per NBM guidance), but
better chances (40-70 percent) of at least 4 inches of snow are
shown for the northern Blue Mountains. Advisory-level snowfall is
possible (10-40 percent chance) across the northern Blue
Mountains. Part of what is driving uncertainty in the amount of
snowfall is the vertical depth of moisture, specifically how far
saturation will extend into the dendritic growth zone (DGZ). While
a couple members of the HREF and REFS do exhibit saturation
through the DGZ, most only extend partially into the zone (or not
at all) which would limit snowfall efficiency.

Mostly dry conditions are expected (70-90 percent chance)
Wednesday into early Thursday morning as high pressure builds
offshore and keeps the Pacific Northwest under a dry northwesterly
flow aloft. Precipitation chances return later Thursday morning as
a shortwave passes over the Northern Rockies and subtropical
moisture gets directed into the region.

By the end of the week, ensemble solutions begin to diverge with
regard to pattern details, but a transition to a more zonal
upper-level pattern is present among all ensemble clusters
beginning Friday and extending through Monday. As far as tangible
weather, this would result in warmer, wetter, breezier
conditions. Of note, EFI values ranging from 0.5-0.8 across the
Columbia Plateau are pointing to decent ensemble agreement in
windy conditions relative to model climatology from 00Z Saturday
to 00Z Sunday. Moreover, NBM probabilistic guidance suggests low-
medium (20-60 percent) chances of advisory-level wind gusts Friday
through Sunday, and there is low potential (10-20 percent chance)
for a high-end wind event late Friday and Saturday across the
region.



&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  40  27  41  29 /  60  10   0   0
ALW  37  28  39  31 /  70  10  10  10
PSC  39  25  37  28 /  20   0   0   0
YKM  44  24  38  27 /  10   0   0   0
HRI  41  27  39  29 /  30   0   0   0
ELN  43  23  37  26 /  10   0   0  10
RDM  46  21  45  26 /  10   0   0   0
LGD  41  26  41  27 /  80  10   0   0
GCD  42  27  42  27 /  50  10   0   0
DLS  50  34  44  36 /  10   0   0   0

&&

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

$$

DISCUSSION...86
AVIATION...82