874
FXUS66 KPDT 202250
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
350 PM PDT THU AUG 20 2026
KEY MESSAGES
- HOT TEMPERATURES THROUGH FRIDAY -- HEAT ADVISORIES IN EFFECT.
- VERY LOW TO SLIGHT CHANCE (5-20 PERCENT) OF HIGH-BASED
SHOWERS AND THUNDERSTORMS FRIDAY AND SATURDAY.
- WIDESPREAD BREEZY TO WINDY WESTERLY WINDS COUPLED WITH LOW
RELATIVE HUMIDITY SATURDAY -- FIRE WEATHER WATCHES IN EFFECT.
DISCUSSION
WATER VAPOR IMAGERY SHOWS A LARGE, CLOSED LOW OFFSHORE IN THE
PACIFIC. 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 SEVERAL DAYS.
UNDER THE RIDGE, WIDESPREAD HOT CONDITIONS ARE IN PLACE WITH
AFTERNOON HIGH TEMPERATURES ALREADY IN THE LOW/MID-90S EARLY
THIS AFTERNOON. TEMPERATURES ARE EXPECTED TO CONTINUE CLIMBING
INTO THE MID/UPPER 90S THIS AFTERNOON, WITH LOCALIZED AREAS
EXCEEDING 100 DEGREES SUCH AS IN HELLS CANYON AND WARM SPRINGS
AREA. HEAT ADVISORIES HAVE BEEN ISSUED FOR THE MAJORITY OF
OUR FORECAST AREA, IN EFFECT THROUGH 10 PM FRIDAY. FRIDAY IS
FORECAST TO BE THE HOTTER DAY ACROSS THE NORTHEAST HALF OF OUR
FORECAST AREA FROM SOUTH-CENTRAL WASHINGTON TO NORTHEAST OREGON,
WITH WIDESPREAD UPPER 90S TO LOWER 100S FORECAST. WHILE
UNCERTAINTY IN PRECISE TEMPERATURES DOES EXIST DUE TO FORECAST
HIGH CLOUDS AND WILDFIRE SMOKE, CONFIDENCE REMAINS MEDIUM-HIGH
(40-80%) IN MAJOR HEATRISK (LEVEL 3 OF 4) FOR THE MAJORITY OF
OUR POPULATION CENTERS WITHIN THE AFOREMENTIONED AREA. THIS
LEVEL OF HEAT AFFECTS ANYONE WITHOUT COOLING/HYDRATION. IN AREAS
THAT AREA NOT LIKELY (20% CHANCE OR LESS) TO SEE MAJOR
HEATRISK, MODERATE HEATRISK (LEVEL 2 OF 4) IS FORECAST (70-90
PERCENT CONFIDENCE); AREAS INCLUDE CENTRAL OREGON AND PORTIONS
OF THE BLUE MOUNTAIN FOOTHILLS IN THE SOUTHWEST HALF OF OUR
FORECAST AREA.
ENSEMBLE NWP GUIDANCE IS IN CONCENSUS THAT THE UPPER LOW WILL
SLOWLY TRACK NORTH-NORTHEAST OVERNIGHT THROUGH FRIDAY AND REMAIN
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 OVERNIGHT THROUGH FRIDAY 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.
WHILE CONFIDENCE WAS ONLY MEDIUM (40-60%) IN REACHING RH
THRESHOLDS, 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 FIRE WEATHER WATCHES DUE TO WIND
AND LOW RELATIVE HUMIDITY FOR THE MAJORITY OF OUR NON-MOUNTAIN
FIRE WEATHER ZONES, IN EFFECT SATURDAY AFTERNOON THROUGH
SATURDAY EVENING. ADDITIONAL HEADLINES MAY BE NEEDED IF
CONFIDENCE INCREASES IN OVERLAP OF CRITICAL WIND/RH THRESHOLDS.
SOME BREEZY CONDITIONS ARE FORECAST TO LINGER SUNDAY AS THE
TROUGH EXITS TO THE EAST.
AVIATION /00Z TAFS THROUGH 00Z SATURDAY/
VFR CONDITIONS PREVAIL WITH LINGERING ELEVATED SMOKE IN THE
REGION. SOME SITES HAVE A SMALL CHANCE (5 TO 15 PERCENT) THAT
ELEVATED SMOKE WILL MAKES IT WAY DOWN TO THE SURFACE AT ANY TAF
SITES, BRINGING MVFR CONDITIONS. GREATEST CHANCE OF OCCURRENCE
WILL BE THE OVERNIGHT HOURS AND LIFT IN THE LATE MORNING TO
AFTERNOON HOURS. OTHERWISE, WINDS WILL BE MOSTLY LIGHT IN
GENERAL AT LESS THAN 12 KNOTS SUSTAINED.
PRELIMINARY POINT TEMPS/POPS
PDT 60 96 64 89 / 0 0 10 10
ALW 65 100 71 92 / 0 0 10 10
PSC 69 100 65 94 / 0 0 10 10
YKM 68 98 69 93 / 0 0 20 20
HRI 67 97 67 91 / 0 0 10 10
ELN 62 95 67 87 / 0 0 20 30
RDM 60 93 54 87 / 0 0 10 0
LGD 58 100 65 94 / 0 0 10 30
GCD 63 100 63 95 / 0 0 10 10
DLS 72 96 66 84 / 0 0 10 10
PDT WATCHES/WARNINGS/ADVISORIES
WA...AIR QUALITY ALERT UNTIL 1 PM PDT FRIDAY FOR WAZ028>030.
HEAT ADVISORY UNTIL 10 PM PDT FRIDAY FOR WAZ024-026>030-521-
523.
FIRE WEATHER WATCH FROM SATURDAY AFTERNOON THROUGH SATURDAY
EVENING FOR WAZ690-691.
OR...AIR QUALITY ALERT UNTIL 1 PM PDT FRIDAY FOR ORZ041-050-502-505-
506-509>511.
HEAT ADVISORY UNTIL 10 PM PDT FRIDAY 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...86
AVIATION...95
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