924
FXUS66 KPDT 272259
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
359 PM PDT Sun Sep 27 2026

.KEY MESSAGES...
- Patchy frost/freezing temperatures possible in Central Oregon
  and Kittitas Valley tonight.

- Warmer high temperatures through the week with zonal/split
  flow aloft.

- Showers (50-70% chance) developing along the Cascades Tuesday
  with a shortwave passing through British Colombia.

&&

.DISCUSSION...
Radar advertising light returns across as a low pressure system
centered around northern California advects moisture across the
Blue and Eastern Mountains through this afternoon. The exiting
of the low pressure system will bring calm, clear conditions
across the region overnight, allowing cooler lows tonight with
the possibility of freezing temperatures in the Kittitas Valley,
Central Oregon, and other low sheltered valleys. Confidence
isn`t too great (only 20-40% chance) that freezing temperatures
will linger in these parts long enough to warrant freeze
warnings. It`s possible with a re-assessment later today/tonight
that we might issue freeze warnings for all or some of these
areas based on if guidance is still aligned or not. For now, we
decided to hold off as of now.

The low will continue to push off to the east through the
remainder of the day, allowing more zonal flow to take place as
a trough digs down from British Colombia and a ridge pushes east
just underneath it. This set-up will allow moderate to heavy
showers to develop in the Cascade region (mostly on the
Washington state side) through Tuesday, with the maximum
potential located around Snoqualmie. Decent chance (50-70%)
we`ll see wetting rains around the Snoqualmie area with QPF`s
advertising up to a half an inch possible through Tuesday and
Wednesday.

As we head later into the week, guidance is in good agreement
(80-90% chance) that the ridge just offshore will continue to
push east, dropping off PoP`s on the later half of the week. The
ridge axis will amplify heading onshore bringing warmer weather
with highs into the low to high 70s through the week, with
calmer winds. Although timing is a bit rough with guidance, the
general picture is the same that we`ll be in a mostly dry
pattern with calm to elevated winds through the week.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
VFR conditions will persist through the forecast period. Winds
will be light and variable through the period with mainly high
clouds with some isolated clearing. DLS will begin to see some
gusty winds after 22Z.

&&

.Preliminary Point Temps/PoPs...
PDT  63  38  71  45 /   0   0   0   0
ALW  64  43  72  52 /   0   0   0   0
PSC  71  37  75  46 /   0   0   0   0
YKM  67  39  73  47 /   0   0   0   0
HRI  68  36  74  48 /   0   0   0   0
ELN  63  31  68  43 /   0   0   0   0
RDM  63  30  71  35 /   0   0   0   0
LGD  65  38  72  39 /   0   0   0   0
GCD  69  37  72  40 /   0   0   0   0
DLS  71  42  75  48 /   0   0   0   0

&&

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

&&

$$

DISCUSSION...95
AVIATION...90