118
FXUS66 KPDT 221108
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
408 AM PDT Sat Aug 22 2026

.KEY MESSAGES...
- Red Flag Warnings in effect for abundant lightning threat
  through this evening for portions of the WA Cascade east
  slopes and the Northern Blues

- Breezy to gusty winds developing today will overlap with low
  relative humidity across lower elevation locations through
  this evening. Red Flag Warnings and wind advisories are in
  effect

- Mostly dry conditions through the remainder of the week, with
  a return of breezy to windy conditions Wednesday

&&

.DISCUSSION...Water vapor imagery tonight shows an upper level
closed low offshore southern OR, while nighttime satellite and
radar imagery show weak, light scattered showers pushing north
across southeast WA and northeast OR.

Today through Sunday: The upper low offshore southern OR will be
the main driver of weather conditions across the PacNW through
Sunday night. Today, shower activity with low chances (5-20%) of
embedded isolated thunderstorms will be focused along the WA
Cascade east slopes, northern Blues, and Wallowa county. The
activity will start early this morning along the WA Cascade east
slopes, then spread east to the Northern Blues and Wallowa
county in the afternoon. Latest CAMs show very weak instability
support in the morning (MUCAPE 100-250 J/kg), but by the
afternoon show modest instability modest instability (MUCAPE
between 250-750 J/kg) developing in the afternoon, with strong
low-level lapse rates (9-10 C/km). Thunderstorms through the
afternoon will be capable of gusty outflow winds and abundant
lightning, which has resulted in the issuance of Red Flag
Warnings.

The upper low lifting up the coast today will also result in a
cross-Cascade pressure gradient to tighten, with winds
strengthening as an associated cooler airmass begins to filter
into the intermountain PacNW. Breezy winds 15-30mph with gusts
30-45mph will develop across the lower elevations through the
afternoon. The strongest winds (sustained winds 25-35mph and
gusts 45-50mph) will develop through the Cascade Gaps into
western portions of the OR columbia Basin this afternoon,
resulting in wind advisories being issued. Confidence is
moderate-high (60-85%) that these strong winds will overlap with
critically low relative humidities across most of our non-
mountain fire weather zones this afternoon. As a result multiple
Red Flag Warnings were issued for the wind/low RH threat across
the Columbia Basin/Gorge, adjacent foothills/valleys, central
OR, and the John Day Basin through this evening.

Late Saturday through Sunday morning, the upper low will become
an open wave trough as it moves inland across WA and northern
OR. A slight chance (15-25%) of light showers will be possible
across the WA Cascade crest Sunday morning. The upper trough
will exit into Canada around the ID/MT border, leaving
behind drier and cooler conditions the remainder of Sunday.
Breezy winds (15-25mph with gusts up to 40mph) will redevelop
through the Cascade gaps through early Sunday evening, with
light winds returning Sunday night.

Monday through Friday: Ensemble cluster guidance is in good
agreement of upper level ridging building back over the PacNW
Monday with dry conditions and a warming trend persisting
through Tuesday. By Wednesday, ensemble cluster solutions are in
good agreement that an upper trough will lift across the PacNW
with a isolated light showers developing along the WA Cascade
crest and breezy winds through the Cascade gaps into the
Columbia Basin and adjacent valleys/foothills. That said,
cluster solutions are in disagreement on passage timing and
location of the trough, resulting in low confidence (25-35%) in
forecast details. Thursday into Friday, cluster solutions favor
a dry southwest flow over the PacNW as broad troughing extends
from western Canada into the northeast Pacific. This will keep
the region dry overall, with diurnally breezy winds through the
Cascade gaps and near normal temperatures. Lawhorn/82

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...VFR conditions to
prevail through the period. Low confidence (15-20%) in
timing/impacts from area smoke at sites through the period.
Winds will increase to 12-17kts with gusts to around 25kts at
sites PDT/RDM/BDN/YKM later this morning through the early
evening. Winds at site DLS will increase to around 20kts with
gusts up to 35kts this afternoon and evening. Winds will remain
light at sites ALW/PSC through the period. Lawhorn/82

&&

.FIRE WEATHER...An upper weather system impacting the region
today will bring the threat of thunderstorms capable of abundant
lightning across WA Cascade crest, northern Blues, and Wallowa
county. In most non-mountain zones, breezy winds will overlap
with critically low relative humidity this afternoon, resulting
in critical fire weather concerns. Multiple Red Flag Warnings
are in effect for abundant lightning and for the wind/RH
threats. RHs will improve slightly and winds weaken Sunday,
though elevated fire weather concerns will remain.

&&

.Preliminary Point Temps/PoPs...
PDT  90  50  83  50 /  10   0   0   0
ALW  93  58  84  57 /   0   0   0   0
PSC  96  58  86  53 /  10   0   0   0
YKM  95  58  86  57 /  30   0   0   0
HRI  92  58  85  52 /  10   0   0   0
ELN  87  54  79  52 /  30   0   0   0
RDM  89  44  84  45 /  10   0   0   0
LGD  95  52  86  50 /  10  10   0   0
GCD  95  53  88  52 /  10   0   0   0
DLS  85  60  84  59 /  10   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...Air Quality Alert until noon PDT Monday for WAZ026-522-523.
     Wind Advisory from 11 AM this morning to 11 PM PDT this
     evening for WAZ024-521.
     Red Flag Warning from noon today to 10 PM PDT this evening for
     WAZ690-691.
     Red Flag Warning from 11 AM this morning to 11 PM PDT this
     evening for WAZ692.
     Red Flag Warning from 10 AM this morning to 8 PM PDT this
     evening for WAZ693.
     Wind Advisory from 2 PM this afternoon to 10 PM PDT this
     evening for WAZ026.
     Red Flag Warning until noon PDT today for WAZ695.
OR...Air Quality Alert until noon PDT Monday for ORZ041-044-049-050-
     502-503-505>507-509>511.
     Wind Advisory from 11 AM this morning to 11 PM PDT this
     evening for ORZ041-044-508-510.
     Red Flag Warning from noon today to 10 PM PDT this evening for
     ORZ691-696-698-700-703.
     Red Flag Warning from 11 AM this morning to 11 PM PDT this
     evening for ORZ692.
     Red Flag Warning from 10 AM this morning to 8 PM PDT this
     evening for ORZ693.

&&

$$

DISCUSSION...82
AVIATION...82
FIRE WEATHER...82