482
FXUS66 KPDT 182243
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
343 PM PDT TUE AUG 18 2026
KEY MESSAGES
- BREEZY WINDS AND LOW RELATIVE HUMIDITY PRODUCING ELEVATED TO
CRITICAL FIRE WEATHER CONDITIONS THROUGH THIS EVENING
- DRYING AND WARMING TREND INTO FRIDAY AS UPPER LEVEL HIGH
PRESSURE BUILDS OVER THE REGION, WITH ELEVATED FIRE WEATHER
CONCERNS DUE TO DRY AND UNSTABLE CONDITIONS
- BREEZY WINDS DEVELOPING SATURDAY, WITH UNCERTAINTY IN
TIMING/EXTENT OF THUNDERSTORMS/SHOWERS FRIDAY THROUGH SUNDAY
MORNING
DISCUSSION
VISIBLE SATELLITE IMAGERY SHOWS MOSTLY CLEAR
SKIES ACROSS THE FORECAST AREA THIS AFTERNOON, THOUGH SEVERAL
SMOKE PLUMES ARE VISIBLE ACROSS THE CASCADE EAST SLOPES AND
IN THE NORTHERN BLUE MOUNTAINS. MEANWHILE, WATER VAPOR IMAGERY
SHOWS AN UPPER LOW OFFSHORE WESTERN CONUS WHILE A SHORTWAVE
TROUGH SLIDES INTO WESTERN MT.
THE SHORTWAVE TROUGH PASSAGE THROUGH THE REGION HAS RESULTED IN
A STRENGTHENING OF THE CROSS CASCADE PRESSURE GRADIENT TODAY.
BREEZY GAP WINDS EXTENDING INTO THE COLUMBIA BASIN WILL PERSIST
THROUGH THE EVENING, THEN DECREASE WITH THE WEAKENING OF THE
SURFACE PRESSURE GRADIENTS OVERNIGHT. THOUGH SEVERAL DAYS OF
THUNDERSTORMS MOVED THROUGH THE AREA, DRY CONDITIONS HAVE
SETTLED BACK INTO THE REGION, AND COMBINED WITH THE BREEZY
WINDS, WILL BRING ELEVATED TO CRITICAL FIRE WEATHER CONDITIONS
THROUGH THE EVENING.
TOMORROW THROUGH THURSDAY, UPPER LEVEL RIDGING WILL BUILD INTO
THE PACNW RESULTING IN A WARMING AND DRYING TREND WITH LIGHT
WINDS. DAYTIME TEMPERATURES WILL RISE INTO THE LOWER TO UPPER
90S IN THE LOWER ELEVATIONS BY THURSDAY, WITH THURSDAY NIGHT
LOWS ONLY COOLING INTO THE LOWER TO MID 60S ACROSS MUCH OF THE
AREA (COOLER IN CENTRAL OR AND MOUNTAIN VALLEYS/BASINS). RISING
LAPSE RATES (AND MIXING HEIGHTS) UNDER THE UPPER RIDGE WILL
BRING ELEVATED FIRE WEATHER CONCERNS ACROSS THE HIGH TERRAIN, AS
THE COMBINATION OF DRY AND UNSTABLE CONDITIONS MAY LEAD TO
INCREASED FIRE BEHAVIOR THROUGH THURSDAY.
FRIDAY THROUGH SUNDAY, ECMWF AND GFS ENSEMBLE MEMBERS ARE IN
GOOD AGREEMENT THAT THE UPPER LOW OFFSHORE WESTERN CONUS WILL
BECOME AN OPEN WAVE AS IT LIFTS INTO THE PACNW, BRINGING WITH IT
ROUNDS OF ISOLATED TO WIDELY SCATTERED THUNDERSTORMS, BREEZY TO
LOCALLY GUSTY WINDS, AND COOLER TEMPERATURES. HOWEVER, AGREEMENT
ON TIMING, INTENSITY, AND LOCATION ARE POOR. GFS ENSEMBLE MEAN
SHOWS IT'S MEMBERS (AND THE DETERMINISTIC) FAVORING THE UPPER
TROUGH COMING INLAND LATE FRIDAY EVENING AND OVERNIGHT,
TRIGGERING NOCTURNAL ISOLATED THUNDERSTORMS ACROSS THE FORECAST
AREA DURING THAT TIME PERIOD. MEANWHILE, ECMWF MEMBERS (AND IT'S
DETERMINISTIC/CONTROL) FAVOR A LATER PASSAGE BY ABOUT 6 TO 12
HOURS, WITH ISOLATED THUNDERSTORMS DEVELOPING VERY EARLY
SATURDAY MORNING ACROSS THE CASCADE EAST SLOPES, THEN LATE
EVENING THUNDERSTORMS DEVELOPING OVER THE BLUES AND WALLOWA
COUNTY. BOTH SOLUTIONS DO FAVOR BREEZY WINDS DEVELOPING THROUGH
THE CASCADE GAPS SATURDAY, WITH ECMWF MEMBERS FAVORING STRONGER
WINDS THEN THOSE OF THE GFS MEMBERS. FORECAST CONFIDENCE IS AT
LEAST MODERATE (45-60%) IN THE UPPER TROUGH PASSAGE OCCURRING
THROUGH THE WEEKEND, HOWEVER THERE IS LOW CONFIDENCE (20-25%)
IN FORECAST DETAILS.
BY NEXT MONDAY, THERE IS MODERATE CONFIDENCE (55-60%) IN UPPER
LEVEL RIDGING BUILDING BACK OVER THE REGION WITH DRY AND WARM
CONDITIONS WITH LIGHT WINDS. LAWHORN/82
AVIATION /00Z TAFS THROUGH 00Z THURSDAY/
VFR CONDITIONS PREVAIL WITH BREEZY WINDS IN DLS AND PDT. WINDS
WILL BE GENERALLY LIGHT AT LESS THAN 12 KNOTS SUSTAINED WITH
ELEVATED SMOKE IN THE REGION. A SMALL CHANCE (5 TO 15 PERCENT)
EXISTS FOR SOME LOW-LEVEL SMOKE BRINGING TEMPORARY MVFR
CONDITIONS FOR ALL TAF SITES.
FIRE WEATHER
BREEZY WINDS THROUGH THE CASCADE GAPS WILL OVERLAP
WITH LOW RH IN THE OR COLUMBIA BASIN, EASTERN GORGE, AND AROUND
WARM SPRINGS THROUGH THIS EVENING. HOT, DRY, AND UNSTABLE
CONDITIONS WILL DEVELOP WEDNESDAY THROUGH THURSDAY AS HIGH
PRESSURE BUILDS OVERHEAD. FRIDAY INTO THE WEEKEND, THERE IS
INCREASING POTENTIAL FOR A RETURN OF ISOLATED THUNDERSTORMS ACROSS
THE AREA, WITH BREEZY TO LOCALLY WINDY CONDITIONS THROUGH THE
CASCADE GAPS AND COLUMBIA BASIN. LAWHORN/82
PRELIMINARY POINT TEMPS/POPS
PDT 54 90 56 93 / 0 0 0 0
ALW 62 92 63 95 / 0 0 0 0
PSC 57 92 56 96 / 0 0 0 0
YKM 59 92 61 96 / 0 0 0 0
HRI 59 92 59 95 / 0 0 0 0
ELN 59 88 59 92 / 0 0 0 0
RDM 47 91 50 94 / 0 0 0 0
LGD 53 93 56 97 / 0 0 0 0
GCD 55 95 57 99 / 0 0 0 0
DLS 60 91 61 96 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...AIR QUALITY ALERT UNTIL 1 PM PDT WEDNESDAY FOR ORZ041-505-506-
509>511.
RED FLAG WARNING UNTIL 10 PM PDT THIS EVENING FOR ORZ691-701-
703.
DISCUSSION...82
AVIATION...95
FIRE WEATHER...82
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