108
FXUS66 KPDT 250507
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1007 PM PDT Thu Sep 24 2026

.KEY MESSAGES...

- Widespread showers and breezy to windy conditions develop
  Friday morning into Friday night. Wind Advisories in effect
  from 8 AM Friday through 11 PM Friday.

- Dry and light wind conditions return this weekend with
  temperatures below normal.

- Mountain showers and at or below seasonal temperatures Monday
  onward

&&

.UPDATE...
Have issued additional Wind Advisories for Friday`s wind event,
in effect for Central Oregon (8AM-5PM) as well as the Lower
Columbia Basin of Washington and the Foothills of the Blue
Mountains of Washington (11AM-11PM).

&&

.DISCUSSION...
Current satellite imagery shows high and mid-level clouds moving
in over the forecast area which might make temperatures cooler
than the forecasted high temperature for the day, while surface
observations are relatively calm and quiet.

Friday...As the upper-level trough and attendant low propagate
inland from the coastal PacNW, there is a chance (80-90%) of
widespread showers across much of Central and northeast Oregon
and into central southern WA early Friday morning. As this
system moves through the area, model guidance and ensembles show
rain showers beginning after midnight near the Cascades with
more widespread rain beginning after 8 AM PDT. There will be a
(70-90%) chance for measurable rain for most of the forecasted
area Friday, with a chance (80-90%) for wetting rain, more so in
the mountainous areas near the Cascades, Ochoco Mountains, and
Southern/Northern Blues. At least 0.05-0.2 inches are forecasted
elsewhere in the forecast area (50-60%). Along with this
precipitation, the upper trough and surface low system will
bring gusty west-southwesterly winds to much of the forecast
area (85-90%). Winds will be 25-30 mph with gusts up to 35-45
mph across the Cascade Gaps and Columbia Basin due to the strong
low-level jet moving through and mixing down to the surface, as
well as the Rattlesnake Ridge and Horse Heaven Hills (85-90%).
Winds will be 15-25 mph with gusts up to 35 mph elsewhere
(70-80%). Yakima and Kittitas Valleys could see gusts 45 mph or
higher but chances are lower (35-40%) Friday afternoon.

Saturday-Sunday...Showers and windy conditions should diminish
late  Friday night into Saturday morning as the upper trough
and low propagate northeast out of the forecast area. Relatively
dry conditions are expected with the upper flow becoming more
westerly bringing light winds back into the area Saturday
morning. Model guidance shows a weak broad trough begin to
develop offshore the PacNW Saturday night, then slide into the
region through Sunday, but due to lack of moisture and strong
upper-level flow, it will mostly be dry with light wind
conditions and temperatures in the low-mid 60s. Ames/01

Monday through Wednesday: Models show the region to be under a
weak  split flow pattern with a ridge to the north of the
region and a trough to the southwest. This will bring continued
dry conditions and light winds through Monday night. In house
calculations show the temperatures to be nearly 5 degrees below
seasonal average Monday with temperatures in the mid to upper
60s with isolated locations in the Basin seeing low 70s.

By Tuesday models are in agreement that the synoptic system will
shift more towards zonal flow. Clusters are in good agreement
with mainly the strength of the incoming system with mainly
timing being the lack of confidence. By Tuesday morning, light
mountain showers will begin over the Washington Cascades before
shifting to the crests of the Blue Mountains with 40% of the
ensembles showing precipitation chances. Temperatures will be
slightly warmer than Monday but still at or near normal seasonal
temperatures in the low 70s (40-60%).

Wednesday models begin to phase apart with GFS showing northwest
flow aloft precipitation along the Cascade crests and a front
coming across the area while the Euro shows continued zonal flow
with precipitation along the WA Cascade crests. NBM appears to
be a bit more in line with the Euro with only showers along the
WA Cascade crests. In house calculations show temperatures to be
at or near seasonal normal with a few isolated locations seeing
slightly above normal temperatures. Temperatures are set to be
in the low to mid 70s (50-60%). 90

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
VFR conditions are forecast through the period. While they
cannot be entirely ruled out, confidence in MVFR CIGs/VSBYs is
low (20% or less) at all sites.

A low-pressure system will bring rain and rain showers to the
region overnight into Friday morning, with some low (10-30%)
chances of lingering post-frontal rain showers through the
afternoon.

Winds will become breezy to very windy at all sites, generally
15-25 kts with gusts of 25-35 kts, by middle to late morning.

&&

.Preliminary Point Temps/PoPs...
PDT  53  69  40  65 /   0  90   0   0
ALW  56  69  45  66 /   0  90  10   0
PSC  55  72  43  69 /   0  70   0   0
YKM  55  65  40  64 /  60  30   0   0
HRI  55  72  43  68 /   0  80   0   0
ELN  51  61  36  60 /  80  50  10   0
RDM  48  59  31  64 /  80  10   0   0
LGD  53  66  38  64 /   0  60   0   0
GCD  53  66  37  67 /   0  50   0   0
DLS  56  66  45  68 /  80  60  10   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...Wind Advisory from 8 AM to 11 PM PDT Friday for WAZ024-027-521.
     Wind Advisory from 11 AM to 11 PM PDT Friday for WAZ028-029.
OR...Wind Advisory from 8 AM to 11 PM PDT Friday for ORZ041-044-507-
     508-510.
     Wind Advisory from 8 AM to 5 PM PDT Friday for ORZ511.

&&

$$

UPDATE...86
DISCUSSION...01/90
AVIATION...86