367
FXUS66 KPDT 040643
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1143 PM PDT Fri Oct 3 2025

.UPDATE...Partial clearing of upslope stratus across central and
eastern Oregon should facilitate some chilly overnight lows for
climatologically cold-prone locations of central Oregon and the
high valleys of the Blue Mountains. Given the current dew points
in the mid-30s to lower 40s and incoming clouds from the north,
confidence is too low (<50%) in observing a widespread freeze for
any of our forecast zones to issue any freeze products. However,
have opted to include mention of frost in the forecast tonight and
tomorrow night as overnight lows are expected (80% confidence) to
dip into the 30s.

The main update to the forecast was to issue Freeze Watches for
central Oregon as well as the Grande Ronde and Wallowa valleys
for Sunday night through Monday morning. Confidence is medium-high
(60-80%) in observing a widespread freeze for the aforementioned
zones. A dry air mass (PWATs of generally 0.40" or less) coupled
with mostly clear skies and light winds should allow temperatures
to drop into the mid-20s to lower 30s. Plunkett/86

&&

.PREV DISCUSSION... /issued 1037 PM PDT Fri Oct 3 2025/

AVIATION...

Westerly surface winds will create upslope stratus along the
crests of the Cascades overnight, as light west to northwest winds
prevail across the area to the east of the range. GOES Nighttime
microphysics RGB is showing patchy stratus east and south of BDN
and RDM into central Oregon. HRRR dewpoint surface depression
trends stay dry with double digit spreads through the early
morning hours, whereas BDN and RDM might have a better shot at
some stratus development with smaller spreads (2-3 degrees) by
10-14z. Considerable HREF probability of ceilings less than 2,000
and 1,000 feet are fairly well removed from the terminal
vicinities, mostly over the higher terrain Saturday morning, so
any stratus near the BDN and RDM terminals will lean VFR. Expect
winds light and variable even into the afternoon, but for DLS
where 20-24 knot gusts will be common in the afternoon. Russell/71

PREV DISCUSSION... /issued 121 PM PDT Fri Oct 3 2025/

DISCUSSION...Skies are clearing across the Basin this afternoon
as a front moves out of the PacNW, while clouds build across the
central and eastern mountains of Oregon as NW flow aloft starts to
prevail. As a result, expect low-end chances (20-40%) for rain
across our mountain zones, followed by a gradual cooldown that may
result in the first hard freeze of the season across our elevated
valley zones by Monday morning.

NBM probabilistic guidance suggests strong odds (>70%) of below
freezing temps across central Oregon and the Wallowa Valley early
Monday morning - two areas that have flirted with a freeze these
last few weeks but have been saved partially by downsloping winds
overnight. With the flow perhaps shifting due north by Monday,
this may allow enough clearing overnight, combined with cold air
advection, to counter the warming effect of any downslope wind. A
little more uncertainty exists for the Grande Ronde Valley, which
typically sees a more pronounced downslope effect overnight and
is thus a bit more sheltered from radiational cooling on nights
like this, but the NBM does mark them for high freezing odds
nevertheless. It`s too early as of now to issue a Freeze Watch,
but could very likely see some issued tomorrow if the forecast
outlook remains the same (which it`s expected to do).

Ensembles then bring in high pressure to kick off next work week,
before bringing in the next round of widespread precip around the
midweek in the form of an offshore low. It`s too early to make
confident predictions on precip amounts, but given the ongoing
haze across the Basin and Yakima Valley, the fires across the WA
Cascades are still in need of wetting rains before we can finally
put a wrap on this wildfire season. Evans/74

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  47  66  42  64 /  10  20  10   0
ALW  49  66  44  65 /  10  20  20  10
PSC  47  70  42  69 /  10   0  10   0
YKM  47  69  42  67 /  20   0   0   0
HRI  48  69  43  68 /  10  10  10   0
ELN  44  66  37  65 /  20   0   0   0
RDM  36  62  32  62 /  10  20   0   0
LGD  40  61  37  62 /   0  20  20  10
GCD  39  59  37  62 /   0  10  10   0
DLS  52  71  48  71 /  20  30   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Freeze Watch from late Sunday night through Monday morning for
     ORZ049-050-511.

WA...None.
&&

$$

UPDATE...86
DISCUSSION...74
AVIATION...71