072
FXUS66 KPDT 212255
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
355 PM PDT Fri Aug 21 2026

.KEY MESSAGES...
- Heat Advisories remain in effect through 10 PM.

- Very low to slight chance (5-20 percent) of high-based showers
  and thunderstorms today and Saturday. Red Flag Warnings in
  effect for several fire weather zones.

- Widespread breezy to windy westerly winds coupled with low
  relative humidity Saturday. Red Flag Warnings in effect for
  numerous fire weather zones. Wind Advisories in effect.

&&

.DISCUSSION...
Water vapor imagery shows a large, closed low offshore in the
Pacific, just west of the OR/CA border. Meanwhile, an upper-
level ridge of high pressure extends from the Four Corners into
the Pacific Northwest. The interaction of these two synoptic-
scale features will drive the bulk of our weather over the next
couple days.

Under the ridge, widespread hot conditions are in place with
afternoon high temperatures already in the 90s to lower 100s
this afternoon. Temperatures are expected to continue climbing
in areas bereft of significant mid/high cloud. Clouds draped
over the western half of our forecast area will suppress daytime
highs relative to yesterday. Heat Advisories remain in effect
through 10 PM this evening due to widespread Moderate (level 2
of 4) to Major (level 3 of 4) HeatRisk. This level of heat
affects anyone without cooling/hydration.

Ensemble NWP guidance is in concensus that the upper low will
slowly track north-northeast through the day, remaining just
offshore. This places the forecast area under southerly to
southwesterly flow aloft. Synoptic-scale forcing coupled with
increasing mid-level moisture may facilitate some high-based
showers and thunderstorms this afternoon, tonight, and into
Saturday morning, but probabilities are quite low (5-15
percent), highest for the Cascades.

The low is then expected (95 percent confidence) to track inland
across northern Oregon and Washington during the day Saturday,
morphing into an open-wave trough as it moves inland. Its
attendant cold frontal passage during the day will help drive
breezy to windy westerly winds through the Cascade gaps as well
as across the Columbia Basin and portions of the Blue Mountains.
Wind Advisories were issued for many public forecast zones
across north-central Oregon and south-central Washington, and
may be expanded should confidence increase in windy conditions
extending farther east across the Columbia Basin and Blue
Mountain foothills.

While confidence was "only" medium-high (50-90%) in reaching rh
thresholds across fire weather zones, due to the magnitude of
the forecast winds (10-25 mph with gusts of 25-40 mph, locally
higher through especially wind-prone areas), have issued Red
Flag Warnings for wind and low relative humidity for the
majority of our non-mountain fire weather zones for later
Saturday morning (OR/WA693) or Saturday afternoon (WA690, WA691,
OR691, OR696, OR698, OR700, and OR703).

In addition to Red Flag Warnings for wind/rh, the potential for
abundant lightning and gusty outflow winds prompted Red Flag
Warnings for WA695 (tonight through Saturday morning) and
OR/WA692 (late Saturday morning through Saturday evening).

Some breezy conditions are forecast to linger Sunday as the
trough exits to the east.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
VFR conditions prevail with lingering smoke in the region.
Elevated smoke may make its way down to the surface overnight,
bringing a slight chance (5 to 15 percent) of MVFR conditions
developing effective for all TAF sites. Breezy to locally windy
conditions will develop in the morning to afternoon hours. Some
sites will develop winds up to 25 to 35 knots of gusts during
the strongest period.


&&

.Preliminary Point Temps/PoPs...
PDT  63  91  50  84 /  10   0   0   0
ALW  70  94  59  85 /  10   0   0   0
PSC  67  96  58  87 /  10  10   0   0
YKM  71  95  58  87 /  10  20   0   0
HRI  69  93  58  86 /  10  10   0   0
ELN  66  88  54  79 /  10  20   0   0
RDM  55  89  45  85 /  10   0   0   0
LGD  65  95  52  87 /  10  20  10   0
GCD  64  95  54  89 /  10   0   0   0
DLS  67  86  60  85 /  10  10   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory until 10 PM PDT this evening for WAZ024-026>030-
     521-523.
     Air Quality Alert until noon PDT Monday for WAZ026-522-523.
     Wind Advisory from 11 AM to 11 PM PDT Saturday for WAZ024-521.
     Red Flag Warning from noon to 10 PM PDT Saturday for WAZ690-
     691.
     Red Flag Warning from 11 AM to 11 PM PDT Saturday for WAZ692.
     Red Flag Warning from 10 AM to 8 PM PDT Saturday for WAZ693.
     Wind Advisory from 2 PM to 10 PM PDT Saturday for WAZ026.
     Red Flag Warning from 11 PM this evening to noon PDT Saturday
     for WAZ695.
OR...Heat Advisory until 10 PM PDT this evening for ORZ041-044-049-
     050-502-503-505>508-510-511.
     Air Quality Alert until noon PDT Monday for ORZ041-044-049-050-
     502-503-505>507-509>511.
     Wind Advisory from 11 AM to 11 PM PDT Saturday for ORZ041-044-
     508-510.
     Red Flag Warning from noon to 10 PM PDT Saturday for ORZ691-
     696-698-700-703.
     Red Flag Warning from 11 AM to 11 PM PDT Saturday for ORZ692.
     Red Flag Warning from 10 AM to 8 PM PDT Saturday for ORZ693.

&&

$$

DISCUSSION...86
AVIATION...95