402
FXUS66 KPDT 230546
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1046 PM PDT WED APR 22 2026
KEY MESSAGES
- MINOR FLOODING INTO THURSDAY ALONG THE UMATILLA RIVER.
- DRIER CONDITIONS RETURN THURSDAY.
- MEDIUM CONFIDENCE (30-60 PERCENT) IN FREEZING TEMPERATURES FOR
THE COLUMBIA BASIN AND BLUE MOUNTAIN FOOTHILLS SATURDAY
MORNING.
UPDATE
WIDESPREAD PRECIPITATION HAS ENDED THIS EVENING AS THE UPPER-
LEVEL LOW PRESSURE SYSTEM THAT BROUGHT AMPLE PRECIPITATION TO
THE REGION OVER THE LAST 36 HOURS HAS EXITED TO THE EAST. CAMS
CONTINUE TO ADVERTISE LOW-MEDIUM POTENTIAL (20-40 PERCENT POPS)
FOR LIGHT UPSLOPE PRECIPITATION INTO THE BLUE MOUNTAINS
OVERNIGHT AND THURSDAY, BUT AS FAR AS AREA STREAMS AND RIVERS
ARE CONCERNED, THE BULK OF THE PRECIPITATION HAS ALREADY FALLEN.
LATEST FORECASTS FROM THE NWRFC HAVE TRENDED DOWNWARD FOR MANY
AREA RIVERS, BASED ON LATEST QPE AND QPF. THE UMATILLA RIVER
UPSTREAM/EAST OF PENDLETON IS NOW FORECAST TO REMAIN AT MINOR
FLOOD STAGE OVERNIGHT INTO THURSDAY, WHILE IN PENDLETON THE
RIVER IS FORECAST TO REMAIN AT BANKFULL/ACTION STAGE.
ELSEWHERE, THE NACHES RIVER NEAR NACHES IS AT BANKFULL/ACTION
STAGE, AND IS FORECAST TO REMAIN SO THROUGH THURSDAY, WHILE
OTHER LOCATIONS ARE NOW EXPECTED TO REMAIN BELOW BANKFULL/ACTION
STAGE.
OPTED TO EXTEND THE AREAL FLOOD ADVISORY FOR THE NORTHERN BLUE
MOUNTAINS THROUGH THE NIGHT DUE TO THE ONGOING MINOR FLOODING.
WINDS REMAIN BREEZY TO LOCALLY WINDY, STILL QUITE GUSTY ALONG
THE MOST WIND-PRONE RIDGES WITHIN THE COLUMBIA BASIN REGION, BUT
ARE FORECAST TO SLACKEN OVERNIGHT.
LOOKING AHEAD, AN ENVIRONMENT CHARACTERIZED BY LOW PWATS
(0.15-0.25 INCHES) COUPLED WITH MOSTLY CLEAR OR CLEAR SKIES AND
PREDOMINANTLY LIGHT WINDS HAS PIQUED MY INTEREST IN FREEZE
POTENTIAL FOR SATURDAY MORNING. MID-LEVEL CLOUD COVER AND
LOCALLY BREEZY NORTHEAST WINDS MAY KEEP TEMPERATURES ABOVE
FREEZING IF THEY MATERIALIZE. AFTER COLLABORATION WITH
SURROUNDING OFFICES, HELD OFF ON ANY FREEZE WATCHES. WILL KEEP
A CLOSE EYE ON THE SET-UP OVER THE NEXT COUPLE DAYS AS
CONFIDENCE IS ALREADY 30-60 PERCENT IN FREEZING TEMPERATURES,
HIGHEST FOR LOW-LYING AND COLD-PRONE PORTIONS OF THE COLUMBIA
BASIN AND BLUE MOUNTAIN FOOTHILLS. 86
DISCUSSION...ISSUED 156 PM PDT WED APR 22 2026
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
THE NIGHT WITH THE LINE ADVANCING AHEAD, THOUGH WINDY
CONDITIONS PERSIST WITH 40-50 MPH GUSTS PREVAILING ACROSS THE
KITTITAS VALLEY 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 POPS
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 WALLOWAS 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 /06Z TAFS THROUGH 06Z FRIDAY/
VFR CONDITIONS ARE FORECAST AT ALL SITES FOR THE NEXT 24 HOURS
AS THE LOW-PRESSURE SYSTEM THAT BROUGHT WIDESPREAD RAIN AND
BREEZY TO WINDY CONDITIONS DEPARTS TO THE EAST OVERNIGHT.
WINDS REMAIN STRONG AND GUSTY AT PDT, BUT ANTICIPATING WINDS TO
DIMINISH OVER THE NEXT SEVERAL HOURS SUCH THAT WINDS AT ALL
SITES WILL BE IN THE 5-15 KT RANGE WITH GUSTS UP TO 25 KTS
THROUGH THE REMAINDER OF THE PERIOD.
CIGS IN THE 5-7 KFT RANGE ARE FORECAST AT PDT/ALW/PSC OVERNIGHT
AND THURSDAY AS A SECOND DISTURBANCE MOVES OVER THE NORTHERN
ROCKIES. CLOUD COVERAGE ELSEWHERE IS FORECAST TO BE MORE FEW-SCT
SHOULD STRATUS DEVELOP. 86
HYDROLOGY...ISSUED 156 PM PDT WED APR 22 2026
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 37 56 / 30 10 20 0
ALW 42 59 38 57 / 40 30 40 10
PSC 42 66 38 62 / 10 10 20 0
YKM 39 67 38 60 / 0 0 10 0
HRI 40 64 38 60 / 10 0 10 0
ELN 40 60 34 56 / 0 0 10 0
RDM 26 63 29 58 / 20 0 0 0
LGD 36 55 35 52 / 90 20 50 10
GCD 32 57 33 53 / 90 0 10 10
DLS 41 65 42 63 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...FLOOD WATCH THROUGH THURSDAY EVENING FOR WAZ029.
OR...FLOOD WATCH THROUGH THURSDAY EVENING FOR ORZ502-507-508.
UPDATE...86
DISCUSSION...95
AVIATION...86
HYDROLOGY...83
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