520
FXUS66 KPDT 092123 CCA
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
223 PM PDT WED SEP 9 2026
KEY MESSAGES
- NEAR-NORMAL TEMPERATURES THURSDAY, WITH BREEZY WESTERLY WINDS
AND LOW RELATIVE HUMIDITY LEADING TO AREAS OF ELEVATED FIRE
WEATHER CONDITIONS IN THE LOWER COLUMBIA BASIN AND ADJOINING
VALLEYS DURING THE AFTERNOON AND EVENING.
- BELOW-NORMAL TEMPERATURES AND WET CONDITIONS LIKELY (60-80%
CONFIDENCE) OVER THE WEEKEND AS AN UPPER-LEVEL LOW MOVES
ACROSS THE PACIFIC NORTHWEST.
- SLIGHT CHANCE (10-25%) OF THUNDERSTORMS OVER THE WEEKEND,
HIGHEST CHANCES FOR THE BLUES AND CASCADES.
DISCUSSION
FORECAST LEADING INTO THURSDAY AFTERNOON SHOWS NEAR NORMAL
TEMPERATURES IN THE MORNING WITH LOWS AROUND LOW-MID 60'S AND
REACHING MID 80'S FOR THE MAX. CURRENT PATTEN SHOWS A ZONAL FLOW
PRESENT BEFORE THE TROUGH MAKES ITS WAY TOWARDS THE PNW COAST,
BRINGING SHOWERS AND SLIGHT CHANCES FOR CONVECTIVE PRECIPITATION
(10% CONFIDENCE). MID THURSDAY INTO THE AFTERNOON SHOWS AN INCREASE
IN WIND SPEED IN THE LOWER COLUMBIA BASIN AND THE ADJOINING VALLEYS
WITH HIGH CONFIDENCE (90-100%) OF BREEZY CONDITIONS (15-25 MPH WITH
GUSTS OF 25-40 MPH). BREEZY CONDITIONS AND LOW RELATIVE HUMIDITY
WILL RESULT IN ELEVATED FIRE WEATHER CONDITIONS BEING PRESENT FOR
THOSE REGIONS (60% - 90% CONFIDENCE). THURSDAY AFTERNOON INTO THE
NIGHT SHOW CHANCE SHOWERS WITH LOW CONFIDENCE (10-20%) FOR THE BLUE
MOUNTAINS AND FOOTHILLS. LEADING UP TO SATURDAY SHOWS AROUND NORMAL
TO COOLER TEMPERATURES PRESENT WITH THE LOWS AROUND THE MID 40'S AN
HIGHS IN THE LOW 70S'.
ENSEMBLE GUIDANCE IS IN EXCELLENT AGREEMENT THAT A DEEP, UPPER-
LEVEL CLOSED LOW WILL BE APPROACHING THE PACIFIC NORTHWEST
SATURDAY MORNING. ENSEMBLE AGREEMENT IS SHORT-LIVED, THOUGH, AS
SPREAD IN ENSEMBLE SOLUTIONS BURGEONS WITH REGARD TO THE TRACK
OF THE LOW BY SATURDAY AFTERNOON. 00Z AND 12Z CLUSTERS OF
SOLUTIONS SUGGEST MEDIUM (50-80%) CONFIDENCE IN THE LOW TRACKING
INLAND SATURDAY THROUGH SUNDAY WITH BELOW-NORMAL TEMPERATURES
AND WIDESPREAD WETTING RAIN (0.10") RESULTING.
FROM SATURDAY MORNING THROUGH SUNDAY NIGHT, NBM PROBABILITIES
INDICATE A LOW MEDIUM (30-60%) CHANCE OF WETTING RAIN FOR MOST
OF THE LOWER ELEVATIONS, WITH HIGHER CHANCES (60-90%) FOR THE
BLUE MOUNTAINS AND THEIR FOOTHILLS AS WELL AS THE CASCADES.
NOTE, THESE PRECIPITATION CHANCES ARE SENSITIVE TO THE TRACK OF
THE LOW, AND 12Z ENSEMBLE GUIDANCE HAS SHOWN A MARKED SHIFT TO
THE NORTHWEST IN THE MEAN TRACK OF THE LOW, AS WELL AS DELAYING
THE INWARD PROGRESSION OF THE LOW. THE MOST NOTABLE, THOUGH
UNLIKELY (5-10% OF MEMBERS) ALTERNATE SCENARIO KEEPS THE LOW
OFFSHORE THROUGH SUNDAY WITH WARMER, DRIER CONDITIONS FOR OUR
REGION. THIS SCENARIO TAKES THE LOW INLAND THROUGH MONDAY WITH
WETTER CONDITIONS ON MONDAY RELATIVE TO THE MORE PROGRESSIVE
SOLUTIONS.
THERE IS A VERY LOW TO SLIGHT CHANCE (10-25%) OF THUNDERSTORMS
SATURDAY AND SUNDAY, WITH THE HIGHEST CHANCES SATURDAY OVER THE
MOUNTAINS.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
VFR CONDITIONS PREVAIL THROUGH THE PERIOD. MOST WINDS WILL BE
SUSTAINED LESS THAN 12 KNOTS THROUGHOUT THE PERIOD. SCT TO BKN
CLOUDS WILL MOVE IN THE AREA THROUGH THE LATTER PART OF THE
PERIOD, BUT CURRENTLY EXPECTING CLOUD HEIGHTS AT 10000 TO 25000
FEET.
PRELIMINARY POINT TEMPS/POPS
PDT 53 83 48 71 / 0 0 10 0
ALW 60 83 53 72 / 0 0 10 0
PSC 55 87 51 76 / 0 0 0 0
YKM 58 81 50 70 / 0 0 0 0
HRI 56 86 52 75 / 0 0 0 0
ELN 57 72 46 67 / 0 0 0 0
RDM 47 84 44 74 / 0 0 0 0
LGD 51 85 46 74 / 0 0 20 0
GCD 52 85 48 76 / 0 0 0 0
DLS 60 82 54 74 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...86/07
AVIATION...95
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