132
FXUS66 KPDT 222225
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
325 PM PDT Thu Oct 22 2026

.KEY MESSAGES...
- Rain and slight chance (10-15%) of thunderstorms today, with
  the best chances of wetting rain (0.10" or greater) over the
  Blue Mountains (90-99% chance) through early Friday.

- Breezy to windy westerly to northwesterly winds late this
  afternoon into Friday, strongest through the Cascade gaps
  where Wind Advisories in effect.

- Widespread near- to sub-freezing low temperatures in the
  Columbia Basin and surrounding lowlands Saturday morning
  (50-95% chance). Freeze Watches issued.

&&

.DISCUSSION...Water vapor imagery shows a large closed low over
central California, and a weak mid-level circulation wrapping
north- northwest around the parent low is evident over southeast
Oregon. Meanwhile, a shortwave trough is approaching the
Pacific Northwest from the northeast Pacific Ocean, and is
forecast to move onshore late this afternoon.

Widespread showers have developed across central to eastern
Oregon and south-central to southeast Washington, and isolated
embedded lightning has been observed over the Blue Mountains and
their adjacent foothills. Modest instability is present (100
J/kg or less MUCAPE per SPC`s RAP-based mesoanalysis), and 12Z
HREF mean forecast values remain below 500 J/kg through the day
(highest for the northeast Blue Mountains). Aside from the
isolated lightning within the ongoing band of showers, the best
chance for notable convection will be this afternoon and
evening across the Blue Mountains region of Grant, Union, and
Wallowa counties; convection developing across southeast Oregon
and southwest Idaho will track north to northeast and the
portion in Oregon may (50% confidence) clip the aforementioned
counties. Main hazards associated with this activity will be
lightning and gusty outflow winds.

Looking ahead to late this afternoon into the evening hours,
breezy to windy westerly to northwesterly winds are forecast to
ramp through the Cascade gaps and across wind-prone portions of
north-central Oregon as pressure gradients increase in strength
(8-11 mb difference between PDX and GEG in latest NWP guidance)
and a modest low-level jet (25-40 kts) develops. Confidence is
medium-high (60-90%) in reaching advisory-level wind gusts (45
mph or greater) through the Kittitas Valley, eastern Columbia
River Gorge, and wind-prone portions of north-central Oregon;
Wind Advisories are in effect from 7 PM this evening until 11 AM
Friday morning.

Precipitation is forecast to taper off through Friday morning
from west to east as the shortwave trough moves overhead, and a
very dry air mass (PWAT of 0.15-0.40") replaces the moist air
mass currently in place. This will set the stage for near- to
sub-freezing temperatures Friday night into Saturday morning.
While most public forecast zones have observed a season-ending
freeze, a widespread freeze has not yet occurred in the lowest
elevations of our forecast area. Given the anticipated dry air
mass, predominantly light winds, and mostly clear skies,
confidence is medium-high (50-95%) that a season-ending freeze
will be observed in the lower Columbia Basin, eastern Columbia
River Gorge, Yakima Valley, and the foothills of the northern
Blue Mountains, so have issued Freeze Watches.

Uncertainty in the 500-hPa height field burgeons Sunday through
early next week due to continued ensemble spread in solutions
regarding the development and evolution of a closed low in the
Gulf of Alaska region. Roughly 50-60% of ensemble members
depict a compact closed low moving inland Monday through mid-
week, while another 20-30% of members show a weaker low, and
the remaining members advertise an upper-level ridge over the
Pacific Northwest. The scenario that shows a stronger closed low
would result in shower chances and cooler temperatures, while
the weaker low would warmer and drier, and the upper-level ridge
would be warm and completely dry.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...VFR conditions
expected through the period. A system passing to the south will
bring rain shower impacts to site PSC through 02Z, and sites
PDT/ALW through 08-09Z tonight. BKN-OVC CIGs are expected to
lower after sunset at sites PDT/ALW this evening, but should
remain AOA 4kft AGL. A cold front passage will bring breezy
conditions to sites DLS/PDT/RDM/BDN/YKM. At site DLS, winds will
increase to 15-25 kts with gusts up to 40kts in the next
several hours and overnight. Sites RDM/BDN will see winds
increase to 12-15 kts with gusts to around 20 kts between
through 13Z. Site YKM winds will increase to 12-15 kts with
gusts to around 23 kts between 03Z-15Z. At site PDT, winds will
increase to 12-15kts with gusts to around 26kts between 08Z-22Z.
Short-term model guidance is indicating low level wind shear
impacts up to 2 kft AGL between 03Z-15Z tonight at site YKM, but
confidence is low-moderate (30-40%) in persistent wind shear
impacts over the site. Lawhorn/82

&&

.Preliminary Point Temps/PoPs...
PDT  36  56  27  58 /  70   0   0   0
ALW  40  57  32  59 /  80   0   0   0
PSC  38  64  29  59 /  50   0   0   0
YKM  39  64  31  58 /   0   0   0   0
HRI  39  61  30  58 /  50   0   0   0
ELN  33  57  26  55 /   0   0   0   0
RDM  25  51  19  60 /  10   0   0   0
LGD  37  53  25  59 / 100  20   0   0
GCD  36  53  25  62 /  90  20   0   0
DLS  43  62  34  63 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...Wind Advisory from 7 PM this evening to 11 AM PDT Friday for
     WAZ024-026.
     Freeze Watch from Friday evening through Saturday morning for
     WAZ024-027>029.
OR...Wind Advisory from 7 PM this evening to 11 AM PDT Friday for
     ORZ041-510.
     Freeze Watch from Friday evening through Saturday morning for
     ORZ041-044-507.

&&

$$

DISCUSSION...86
AVIATION...82