673
FXUS66 KPDT 222249
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
349 PM PDT WED APR 22 2026
KEY MESSAGES
- LIGHT TO MODERATE RAINFALL WITH BREEZY TO LOCALLY WINDY
CONDITIONS WILL CONTINUE THROUGH THE LATE AFTERNOON TO
EVENING HOURS ACROSS PARTS OF THE COLUMBIA BASIN AND BLUE
MOUNTAINS.
- HYDRO CONCERNS ALONG THE NACHES AND UMATILLA RIVERS.
- A DRIER AND WARMER PATTERN IS EXPECTED THURSDAY!
DISCUSSION
CURRENT RADAR SHOWS A LINE OF LIGHT TO MODERATE RAIN CONTINUING
TO FALL IN THE COLUMBIA BASIN DOWN THROUGH THE BLUE MOUNTAINS.
THE KITTITAS AND YAKIMA VALLEYS HAVE DRIED OUT FOR THE REST OF
NIGHT WITH THE LINE ADVANCING AHEAD, THOUGH WINDY CONDITIONS
PERSIST WITH 40-50 MPH GUSTS PREVAILING ACROSS THE KITTITAS
THROUGH THE EVENING HOURS. NEAR THE NORTHERN BLUE MOUNTAINS,
STRONG OROGRAPHIC LIFT HAS ENABLED CONTINUOUS MODERATE RAINFALL
EMBEDDED WITH GUSTY 35-45 MPH WINDS THROUGH THE MORNING TO
AFTERNOON HOURS. OBSERVATIONS FROM THE PAST 12-HOURS SHOWS THAT
MULTIPLE SITES ALREADY RECEIVED 1 INCH OR GREATER OF PRECIP THAT
INCLUDE MEACHAM, BOILING POINT, AND EMIGRANT SPRINGS. HIGH
CONFIDENCE (>90% CHANCE) THAT THE NORTHERN BLUES WILL SEE AT
LEAST AN ADDITIONAL 1.7 TO 2.7 INCHES OF PRECIP THROUGH TONIGHT
WITH THE HREF 24-HOUR PRECIP SHOWING 1.3 TO 1.5 INCHES IN THE
25TH PERCENTILE. AT THE 75TH PERCENTILE THAT JUMPS TO 1.7 TO 2.2
INCHES. WINDS WILL CONTINUE TO BE BREEZY TO LOCALLY WINDY
ACROSS THE OR FOOTHILLS, KITTITAS VALLEY AND BLUES WITH WINDS
DECREASING BELOW ADVISORY LEVEL IN THE LATER EVENING HOURS (>90%
CONFIDENCE).
SYNOPTICALLY, A RIDGE PROTRUDING INTO THE PACNW & BRITISH
COLUMBIA AREA IN A SIDEWAYS REX PATTERN WILL TAPPER DOWN POP'S
THROUGH EARLY NEXT WEEK. MODEL CLUSTER SUPPORT A CUTOFF LOW IN
THE ALBERTA AREA WILL BRING THE AREA IN-BETWEEN THE TWO SYSTEMS
WITH THE RIDGE KEEPING MOST OF THE REGION DRY WHILE THE LOW TO
THE EAST WILL BRING LIGHT SNOW SHOWERS INTO THE WALLOWA'S AND
PARTS OF THE NORTHERN BLUES. ALL OF THE LREF CLUSTERS TELL A
SIMILAR STORY THROUGH EARLY NEXT WEEK WITH KEEPING THE COLUMBIA
BASIN DRY WITH SOME LIGHT SNOW SHOWERS AND RAIN ACROSS THE
MOUNTAINOUS REGIONS (THAT INCLUDES CENTRAL OREGON). NOT SEEING
ANYTHING IN THE WAY OF ANY MAJOR IMPACTS OR HIGHLIGHTS THROUGH
EARLY NEXT WEEK AT THIS TIME WITH THE RIDGE STILL PRESENT AND
PREVENTING ANY MAJOR QPF SYSTEMS TO DEVELOP.
AVIATION /00Z TAFS THROUGH 00Z FRIDAY/
CONDITIONS RANGE FROM VFR (MOST AREAS) TO MVFR AND EVEN SOME IFR
ACROSS THE REGION AS LOW PRESSURE AND RAIN IMPACT THE AREA.
LATEST RADAR IMAGERY SHOWED THE BACK EDGE OF THE PRECIPITATION
HAS MADE IT THROUGH PSC AND WAS WORKING ITS WAY S AND E.
CONDITIONS ARE EXPECTED TO IMPROVE THIS EVENING.
WINDS WILL CONTINUE TO GUST, BUT WILL GRADUALLY LESSEN AND MOST
LOCATIONS WILL BE AROUND 10 KTS BY MORNING, WITH DLS BEING THE
ONLY EXCEPTION.
THE OTHER STORY IS THE GUSTY WINDS, MAINLY FROM THE SOUTHWEST TO
NORTHWEST ACROSS THE TAF SITES. THESE WINDS HAVE BEENS AS HIGH
AS 40 TO 45 KTS ACROSS THE REGION. WINDS WILL REMAIN GUSTY
THROUGH THE AFTERNOON AND EVENING HOURS BEFORE DECREASING
SOMEWHAT OVERNIGHT. HOWEVER, WINDS IN THE 15 TO 25 KT RANGE WILL
BE PREVALENT THROUGH THE OVERNIGHT HOURS.
HYDROLOGY
RAINFALL HAS BEEN LESS THAN FORECAST BUT HAS STILL BEEN
SUBSTANTIAL. RAIN AMOUNTS HAVE BEEN UP TO 2 INCHES IN THE BLUE
MOUNTAINS AND UP TO AN INCH IN THE BLUE MOUNTAIN FOOTHILLS SO FAR
AND ANOTHER HALF INCH TO INCH OF RAIN IS POSSIBLE THROUGH THIS
EVENING. THIS HAS CAUSED STREAMS AND RIVERS TO RISE. THE UMATILLA
RIVER AT GIBBON IS FORECAST TO APPROACH MODERATE FLOOD STAGE THIS
AFTERNOON, THOUGH WITH REDUCED RAINFALL AMOUNTS, CONFIDENCE IS LOW
TO MEDIUM (30%-40%) OF APPROACHING MODERATE FLOOD STAGE. CONFIDENCE
IS 70% TO 80% THAT THE UMATILLA AT GIBBON WILL REACH MINOR FLOOD
STAGE. THE UMATILLA RIVER AT PENDLETON IS FORECASTED TO REACH MINOR
FLOOD STAGE BY A FEW INCHES BRIEFLY BETWEEN 9 PM AND 5 AM TONIGHT.
CONFIDENCE IS ONLY ABOUT 50% OF THIS HAPPENING. THE GRANDE RONDE
RIVER AT TROY, THE JOHN DAY RIVER AT SERVICE CREEK AND THE WALLA
WALLA RIVER AT TOUCHET RIVER ARE ALL EXPECTED TO EXCEED BANKFULL
TONIGHT AND TOMORROW. THE FIRST TWO ONLY EXCEED IT BY A FEW INCHES.
THE WALLA WALLA RIVER AT TOUCHET GETS TO WITHIN A HALF FOOT OF MINOR
FLOOD STAGE, BUT WITH RAINFALL TRENDING LOWER THAN ANTICIPATED, DO
NOT BELIEVE IT WILL REACH MINOR FLOOD STAGE. ELSEWHERE, THE FORECAST
FOR THE NACHES RIVER AT CLIFFDELL HAS BEEN LOWERED TO JUST BELOW
ACTION STAGE. THE NACHES RIVER AT NACHES IS FORECAST TO GET ABOUT A
HALF FOOT ABOVE BANKFULL TOMORROW MORNING BUT SHOULD NOT CAUSE ANY
SIGNIFICANT FLOODING. 83
PRELIMINARY POINT TEMPS/POPS
PDT 39 59 38 56 / 40 20 20 10
ALW 42 59 39 57 / 50 40 30 20
PSC 42 66 40 63 / 20 20 10 0
YKM 39 67 40 60 / 0 0 10 0
HRI 40 64 39 60 / 20 10 10 0
ELN 39 60 35 57 / 0 0 10 0
RDM 26 62 29 59 / 10 0 0 0
LGD 36 54 35 51 / 90 30 50 20
GCD 31 56 32 53 / 80 0 10 10
DLS 41 66 42 64 / 10 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...WIND ADVISORY UNTIL 11 PM PDT THIS EVENING FOR WAZ024-026-029-
521.
FLOOD WATCH THROUGH THURSDAY EVENING FOR WAZ029.
WINTER WEATHER ADVISORY UNTIL 8 PM PDT THIS EVENING FOR WAZ030.
OR...WIND ADVISORY UNTIL 11 PM PDT THIS EVENING FOR ORZ041-044-507-
508-510.
FLOOD WATCH THROUGH THURSDAY EVENING FOR ORZ502-507-508.
WINTER WEATHER ADVISORY UNTIL 8 PM PDT THIS EVENING FOR ORZ502-
503.
DISCUSSION...95
AVIATION...77
HYDROLOGY...83
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