265
FXUS66 KPDT 120357
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
857 PM PDT FRI SEP 11 2026
KEY MESSAGES
- SCATTERED RAIN SHOWERS AND ISOLATED THUNDERSTORMS DEVELOPING
SATURDAY EVENING AND RAIN SHOWERS BECOMING MORE NUMEROUS
THOUGH SUNDAY MORNING.
- WIDESPREAD WETTING RAIN SATURDAY NIGHT AND SUNDAY
- BREEZY TO WINDY ACROSS THE EASTERN COLUMBIA RIVER GORGE
SATURDAY NIGHT AND SUNDAY MORNING.
UPDATE
THE INCOMING SYSTEM CONTINUES TO TREND TOWARDS A WETTER
SCENARIO, WHICH IS ADVERTISED BY A 20-30% INCREASE IN
PRECIPITABLE WATER VIA THE AI ECMWF ENSEMBLES OVER THE LAST 24
HOURS. THIS IS A DIRECT RESULT OF INCREASED RESONANCE TIME NEAR
A CLOSED LOW PRESSURE SYSTEM FURTHER OFFSHORE OVER THE EASTERN
PACIFIC. THE DELAY HAS ALSO ATTRIBUTED TO A STRONGER TRANSIENT
RIDGE OF HIGH PRESSURE BUILDING AHEAD OF THIS SYSTEM, WHICH WILL
ALLOW FOR THUNDERSTORM DEVELOPMENT ACROSS THE BLUE MOUNTAINS AND
LEADING TO INCREASED POTENTIAL FOR HEAVY DOWNPOURS IN AND AROUND
FIRE SCARS OF THE PARADISE AND HAGEN WILDFIRES. THE REFS
SUGGESTS CONVECTION BEGINNING AROUND 6 PM AND EXTENDING UNTIL
SHORTLY AFTER MIDNIGHT. AS A RESULT, A FLOOD WATCH HAS BEEN
ISSUED ACROSS BOTH BURN SCARS FROM SATURDAY AFTERNOON THROUGH
SUNDAY EVENING AS RAIN RATES OF AROUND 0.5"/HOUR MAY BE ACHIEVED
WITHIN A DEVELOPED RAIN CORE. 75
DISCUSSION
REGIONAL RADAR WAS CLEAR THIS AFTERNOON WITH GOES SATELLITE DAY
CLOUD PHASE SHOWING THIN HIGH LEVEL CLOUDS SPREADING EAST
ACROSS THE UPPER COLUMBIA BASIN. EASTERN WA EASTERN OR, WHILE
MOST OF CENTRAL OREGON AND THE SOUTHERN BLUE MTS WERE
CLEAR/SUNNY. THE WEAK ZONAL FLOW ALOFT ACROSS THE REGION TODAY
WILL BE DISRUPTED AS AN UPPER LOW SPREADS ONTO THE OREGON COAST
BY LATE SATURDAY AFTERNOON AND EVENING, PLACING THE INTERIOR NW
UNDER A BROAD AREA OF PVA ADVECTION/DIFFLUENCE ALOFT. THE
SHOWERS THAT ARE ALREADY GOING ON TODAY WEST OF THE CASCADES
WILL BE DIURNAL IN NATURE, SO NO RAIN IS ANTICIPATED OVERNIGHT.
INCREASINGLY BROAD SCALE LIFT AND MOISTURE TRANSPORT WILL
PROMOTE INSTABILITY ON SATURDAY, ENOUGH SO FOR ISOLATED TO
WIDELY SCATTERED THUNDERSTORM AND WIDESPREAD WETTING RAINS FROM
FEW TENTHS OF AN INCH TO POTENTIAL FOR OVER AN INCH IN THE
MOUNTAIN ZONES THOUGH THE DAY ON SUNDAY, ONCE THE UPPER SYSTEM
EXITS THE REGION. INITIALLY A FEW SHOWERS ARE POSSIBLE ALONG THE
CASCADE CREST, BUT EVERYWHERE FARTHER EAST WILL BE DRY THROUGH
ABOUT THE END THE AFTERNOON SATURDAY. HREF (ENSEMBLES) SHOW A
RAMP UP IN THE MEAN 1 HOURLY PRECIPITATION FIELDS BETWEEN ABOUT
5 AND 9 PM, ACROSS THE EASTERN SLOPES, THE COLUMBIA BASIN AND
FOOTHILLS OF THE BLUE MTS. THERE IS NOTHING ALL THAT ANOMALOUS
WITH THE PWATS FOR THIS SYSTEM. ABOUT A 1 STANDARD DEVIATION IN
PRECIPITABLE WATER SHOWS UP ACROSS THE CASCADES AND THE EASTERN
MTS SATURDAY AFTERNOON/EVENING AND SPREADING NORTH INTO EASTERN
WA THOUGH SUNDAY MORNING AS THE COLD CONVEYOR BELT LIFTS ACROSS
THE PALOUSE. TRENDS FOR THUNDER CONTINUE TO BE PUSHED BACK IN
TIME AS THE 12Z HREF NOW SHOWS 4HR CALIBRATED THUNDER (10 TO
30%) AROUND 6Z (NEARING MIDNIGHT SATURDAY) OR SO FOR THE
FOOTHILLS OF THE BLUES. THE PERIOD OF HEAVING RAINFALL WILL BE
BETWEEN MIDNIGHT SATURDAY AND ABOUT NOON SUNDAY WITH MODEL
SPREADS FAIRLY LARGE. UNCERTAINTY AT THE TRI-CITIES IS A RANGE
OF (USING 25TH TO 75TH PERCENTILE) ANYWHERE FORM AT LEAST ABOUT
A QUARTER OF AN INCH TO AND INCH AND AND QUARTER BY LATE SUNDAY
EVENING. THAT UNCERTAINTY/SPREAD IS COMPRESSED A BIT OVER THE
MOUNTAIN ZONES. FOR INSTANCE AT LA GRANDE WHERE AT LEAST ONE
HALF INCH CAN BE EXPECTED WITH A HIGHER OUTCOME AROUND AN INCH
AN A QUARTER OF RAINFALL. RAINFALLS OF AROUND AN INCH ARE FAIRLY
LIKELY (ABOVE ABOUT 60%) FOR THE PARADISE/HAGAN FIRE AREAS.
WESTERLY WINDS RAMP UP THROUGH THE GAPS ON SATURDAY EVENING AS
WELL WITH THE STRONGER PERIOD RUNNING FROM AROUND MIDNIGHT
SATURDAY THOUGH LATE MORNING SUNDAY MORNING. THE NBM MEAN SHOWS
POTENTIAL FOR SUSTAINED WINDS IN EXCESS OF 30 MPH AND GUST IN
EXCESS OF 40 MPH HOWEVER THESE STRONGER WINDS ARE LIMITED TO THE
HIGHER RIDGE-TOPS ALONG THE GORGE. MOST OTHER AREAS LOOK BREEZY
AND FALLING UNDER THE GENERAL WIND ADVISORY CRITERIA. THE WET
REGIME WILL HAMPER TEMPERATURES SUNDAY, WHERE MID 60S WILL BE
THE HIGHEST TEMPS ACROSS THE THE KITTITAS VALLEY, CENTRAL OREGON
AND PARTS OF THE BASIN. DRY WEATHER AND PLEASANT TEMPERATURES,
WITH NOT A LOT OF WIND WILL FINISH OUT THE BALANCE OF THE WEEK
BEFORE NBM TRENDS TOWARD A WARMUP BY THE NEXT WEEKEND.
AVIATION /00Z TAFS THROUGH 00Z SUNDAY/
VFR CONDITIONS ARE FORECAST THROUGH THE TAF PERIOD. WINDS AT
ALL SITES EXCEPT RDM, BDN, AND KDLS WILL BE LOWER THEN 10 KTS.
BDN AND RDM WILL EXPERIENCE GUSTING CONDITIONS OF UP TO 20 KTS
FROM THE 22Z TO 00Z TIMEFRAME, WITH DLS REACHING 15 KTS. LOW
CONFIDENCE (10-30%) IN RAIN SHOWERS FOR YKM, DLS, BDN, AND RDM
STARTING AROUND 22-00Z, WITH A PROB30 BEING ISSUED FOR YKM.
PRELIMINARY POINT TEMPS/POPS
PDT 47 76 45 61 / 0 0 90 80
ALW 52 79 49 60 / 0 0 90 90
PSC 50 80 47 63 / 0 0 90 90
YKM 54 76 50 63 / 0 10 90 100
HRI 49 79 46 63 / 0 0 100 80
ELN 48 72 44 59 / 0 0 100 100
RDM 40 71 36 60 / 0 10 80 10
LGD 47 81 44 59 / 0 0 90 80
GCD 46 81 43 59 / 0 0 100 40
DLS 54 77 51 66 / 0 20 90 60
PDT WATCHES/WARNINGS/ADVISORIES
WA...FLASH FLOOD WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY
EVENING FOR WAZ030.
OR...FLASH FLOOD WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY
EVENING FOR ORZ502.
UPDATE...75
DISCUSSION...71
AVIATION...86
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page