952
FXUS66 KPDT 211130
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
330 AM PST Fri Nov 21 2025


.AVIATION...

Latest surface analysis showed a 1024hPa surface high pressure
centered squarely over the Columbia Basin. This pattern is
anticipated to perist over the next 24 hours. Although winds will
be light and terrain driven, fog and low stratus will be a low
confidence forecast problem this morning. The best case for this
fog and stratus is around the BDN and RDM terminals, which is
reasonably pointed to in the HREF probability of low visibility
and ceiling plots. All other terminals are basically devoid of a
decent signal, however a few have already had brief periods of fog
OR CIGS dropping into the IFR category or lower. The surface
inversion breaks around 10 am.

&&

.PREV DISCUSSION... /issued 153 AM PST Fri Nov 21 2025/

DISCUSSION...Quiet weather is expected to prevail heading into the
weekend as a high pressure ridge settles over the PacNW. So long as
skies remain clear, however, conditions will be ripe with overnight
low stratus and fog development, which can already be seen early
this morning in central Oregon and along the Columbia River. With
high pressure in place, these low clouds will struggle to lift as
well, so many of our low-lying areas may see overcast conditions
persist well into the day once they form. Have already issued a
Dense Fog Advisory for central Oregon, and expectation is that
coverage will only spread over the coming days.

As far as precipitation chances are concerned, the ridge is broad
enough to welcome at least some moisture advection into the central
Washington Cascades, but should note that guidance has scaled back
PoPs quite a bit compared to previous runs, so current thinking is
that the next best chance for area-wide precip will arrive with a
cold front sometime around the Sunday afternoon and early evening
hours. Models are coming into better agreement with this system, but
still differ slightly on the attendant trough`s amplitude, so
confidence on QPF is only moderate (40-50%), but as of now, given
the quick-moving nature of the system, most impacts will be directed
to the Cascades and eastern mountains. Snow levels will fall as cold
air rushes in behind the front, down to 2500-3000 ft by early Monday
morning, so some accumulations are expected along our mountain
passes, albeit only a couple of inches at best for primarily the
Washington Cascade passes given the system`s speed and precip
transition from rain during the day to snow overnight into Monday.
Winds will be breezy as well, but are expected to remain below
advisory criteria at this time.

Ensembles are still not in great agreement beyond Monday, but do
favor some sort of ridging pattern through the midweek. Whether or
not the ridge axis will allow for moisture advection into the
forecast area is uncertain, however. Should note that by the end of
next week, both the deterministic GFS and ECMWF hint towards a cold
spell, but much could change across guidance between now and then.
74

AVIATION...Updated 06z TAFs...Dense fog has formed around RDM and
BDN, where a Dense Fog Advisory has been issued. Fog and low
cigs/vsbys could persist there through the late morning. Satellite
imagery also reveals pockets of low clouds and fog developing
around the Columbia River, elevated valleys within the Basin, and
foothills of the Blue Mountains. Confidence is low-moderate in fog
at sites outside of RDM and BDN, but should note that the current
weather pattern does support fog formation across much of the
area. Where low clouds do not develop, VFR conditions are
expected to prevail. 74

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  50  30  50  32 /   0   0   0   0
ALW  48  35  48  36 /   0   0   0   0
PSC  48  29  45  31 /   0   0   0   0
YKM  48  29  47  32 /   0   0   0   0
HRI  47  30  46  31 /   0   0   0   0
ELN  47  30  47  32 /   0   0   0  10
RDM  51  23  56  27 /   0   0   0   0
LGD  51  30  53  34 /   0   0   0   0
GCD  50  29  55  30 /   0   0   0   0
DLS  50  35  51  38 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Dense Fog Advisory until 10 AM PST this morning for ORZ511.

WA...None.
&&

$$

DISCUSSION...74
AVIATION...71