035
FXUS66 KPDT 280514
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1014 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 /06Z TAFS THROUGH 06Z TUESDAY/...

Light and variable winds under 6 knots are the most likely winds
overnight before mixing develops on Monday and more westerly
momentum develops through the Columbia River Gorge. DLS can see
west winds gusting to near 26 knots by late afternoon.
Otherwise, expectations for VFR conditions is of at least an 80%
confidence level though the TAF period at all terminals.


&&

.Preliminary Point Temps/PoPs...
PDT  39  70  44  75 /   0   0   0   0
ALW  45  71  51  75 /   0   0   0   0
PSC  40  75  45  77 /   0   0   0   0
YKM  43  73  46  73 /   0   0   0   0
HRI  39  74  48  76 /   0   0   0   0
ELN  37  68  43  64 /   0   0   0  20
RDM  31  71  36  75 /   0   0   0   0
LGD  39  71  39  75 /  10   0   0   0
GCD  39  72  40  76 /   0   0   0   0
DLS  46  76  48  73 /   0   0   0   0

&&

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

&&

$$

DISCUSSION...95
AVIATION...71