591
FXUS66 KPDT 211650
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
950 AM PDT Fri Aug 21 2026

.KEY MESSAGES...
- Hot temperatures Today -- Heat Advisories in effect.

- Very low to slight chance (5-20 percent) of high-based showers
  and thunderstorms Today and Saturday.

- Widespread breezy to windy westerly winds coupled with low
  relative humidity Saturday -- Fire Weather Watches in effect.

&&

.DISCUSSION...
An upper 500 mb ridge continues to drive the hot weather across
the region for another day as temperatures Today are expected
to be the hottest of the week. Widespread 90s will be common
with hotter 100 to 105 degree temperatures across the Columbia
Basin region of Benton, Franklin and Walla Walla counties of WA.

An upper low over the eastern Pacific will reach the OR/WA
coast by midday Saturday, pushing the upper ridge east, cooling
aloft and creating conditions for shower and thunderstorms
especially across the higher terrain mountains zones. By 12z
Saturday showers and thunderstorm chances increase to around
5-15% over the WA Cascades and to 20% by 18z across both the WA
Cascades and the Eastern Blue Mountains of OR/WA. HeatRisk is
in the 2 to 3 category Today with widespread Heat Advisories in
effect as temperatures range from the 90s to the low 100s across
the forecast area.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Conditions initialize at VFR. Elevated smoke prevails across
the region with 6 to 8 SM visibilities across sites in Central
OR through the Foothills of the Blues, which will not take much
to put into MVFR over the next few hours. Conditions will
improve when daytime mixing lifts the smoke by the later morning
to the early afternoon hours. Breezy winds develop in the
Cascade gaps in DLS by 07Z with 20 to 30 knot gusts developing.

&&

.FIRE WEATHER...
Combined probabilities for specific wind thresholds and low
relative humidity develops Saturday Afternoon, across the
Columbia Basin of Washington and Oregon, the Yakima valley and
central Oregon. The critical fire weather conditions are
expected through mid evening Saturday and fire weather watches are
in effect for OR696, OR698, AND OR700 OR691, OR703, WA690, AND
WA691. Fire weather risk owing to lightning is possible across
the WA695 zone where about a 20% chances for thunderstorms along
the WA Cascades eastern slopes.

&&

.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...Air Quality Alert until 1 PM PDT this afternoon for WAZ028>030.
     Heat Advisory until 10 PM PDT this evening for WAZ024-026>030-
     521-523.
     Fire Weather Watch from Saturday afternoon through Saturday
     evening for WAZ690-691.
     Fire Weather Watch from this evening through Saturday
     afternoon for WAZ695.
OR...Air Quality Alert until 1 PM PDT this afternoon for ORZ041-050-
     502-505-506-509>511.
     Heat Advisory until 10 PM PDT this evening for ORZ041-044-049-
     050-502-503-505>508-510-511.
     Fire Weather Watch from Saturday afternoon through Saturday
     evening for ORZ691-696-698-700-703.

&&

$$

DISCUSSION...71
AVIATION...95
FIRE WEATHER...71