255
FXUS66 KPDT 221741
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1041 AM PDT WED APR 22 2026
KEY MESSAGES
1. CONTINUED RAINFALL THROUGH WEDNESDAY EVENING
2. BREEZY TO WINDY CONDITIONS WEDNESDAY
3. PATTERN SHIFT WILL BRING DRIER AND BELOW AVERAGE TEMPERATURES.
DISCUSSION
CURRENT RADAR SHOWS SOME MODERATE RETURNS OVER THE BASIN WITH GROUND
OBSERVATIONS SHOWING 0.12-0.16 INCHES OF RAINFALL HAS FALLEN BETWEEN
PASCO AND WALLA WALLA IN THE LAST HOUR. ELSEWHERE, RADAR SHOWS
LIGHTER RETURNS WITH 0.03-0.07 INCHES OF RAINFALL IN THE LAST HOUR
WITH HIGHER AMOUNTS THROUGH MEACHAM. RAINFALL IS EXPECTED TO
CONTINUE THROUGH THE DAY TODAY.
MODELS SHOW THE CLOSED LOW TO BE OFF THE COAST OF NORTHERN
CALIFORNIA WITH THE LEADING EDGE SPINNING DIRECTLY ACROSS THE
REGION. SOUTHEAST FLOW IS BRINGING WIDESPREAD RAIN ACROSS THE
REGION CURRENTLY AND MODELS SHOW PRECIPITATION TO CONTINUE THROUGH
MUCH OF THE DAY. RAINFALL AMOUNTS WILL VARY ACROSS THE REGION WITH
HEAVIEST AMOUNTS FOCUSED ACROSS THE BLUES AND PORTIONS OF THE
EASTERN MOUNTAINS DECREASING LIGHTLY AS WE MOVE WESTWARD. LIGHTEST
AMOUNTS WILL BE FOUND THROUGH CENTRAL AND NORTH CENTRAL OR UP TO THE
WESTERN PORTION OF THE GORGE. NBM QPF SHOWS PLENTY OF PRECIPITATION
AVAILABLE WITH 60-90% OF THE NBM RAW ENSEMBLES SHOWING RAINFALL
TOTALS NEARING 1-1.5 INCHES OVER THE NEXT 24 HOURS ALONG THE CRESTS
OF THE NORTHERN BLUES. THE FOOTHILLS SHOW 40-60% PROBABILITIES OF
NEAR AN INCH OF RAINFALL WHILE THE EASTERN PORTION OF THE COLUMBIA
BASIN SEES 40-60% FOR 0.80-1 INCH WHILE THE WESTERN PORTION OF THE
COLUMBIA BASIN OF WA HAS 40-60% PROBABILITIES OF SEEING NEAR 0.50
INCHES OF TOTAL RAINFALL. MOVING TO THE SIMCOE HIGHLANDS OF
KLICKITAT AND YAKIMA KITTITAS VALLEYS, 40-60% PROBABILITIES THESE
AREAS WILL SEE UP TO 0.40 INCHES OF RAINFALL. AS FOR CENTRAL AND
NORTH CENTRAL OR, 60-80% CHANCES OF 0.01-0.02 INCHES. A QUICK NOTE,
SNOW LEVELS HAVE BEGUN TO DECREASE TO AROUND 4500 FEET AND
PRECIPITATION ABOVE THAT WILL LIKELY FALL AS WET SNOW. A WINTER
WEATHER ADVISORY IS IN EFFECT FOR THE NORTHERN AND SOUTHERN BLUES
FOR 7 TO 12 INCHES AND 4 TO 8 INCHES RESPECTIVELY THROUGH 8 PM.
A WIND ADVISORY IS IN EFFECT FOR THE KITTITAS/YAKIMA VALLEYS, BLUE
MOUNTAIN FOOTHILLS, COLUMBIA GORGE AND BASIN, NORTH CENTRAL OR AND
THE SIMCOE HIGHLANDS OF KLICKITAT COUNTY. SUSTAINED WINDS OF 25 TO
35 MPH WITH GUSTS OF 40 TO 55 MPH EXPECTED. IN HOUSE MODELS GUIDANCE
SHOWS A 12-14 MB PRESSURE GRADIENT CHANGE OVER THE REGION WILL LEAD
IN INCREASED WINDS, ESPECIALLY THROUGH THE WIND PRONE MOUNTAIN GAPS
AND FOOTHILLS. NBM RAW ENSEMBLES SHOW 70-80% PROBABILITIES OF THE
WINDS OCCURRING WITH GROUND OBSERVATIONS ALREADY SHOWING KITTITAS
VALLEY HAVING WINDS IN THE 25-30 MPH SUSTAINED WINDS AND GUSTS THAT
HAVE ALREADY REACHED 43-45 MPH. WINDS ARE EXPECTED TO REMAIN
ELEVATED THROUGH 11 PM WEDNESDAY NIGHT.
AS WE MOVE INTO WEDNESDAY NIGHT AND THURSDAY MORNING THE UPPER LEVEL
LOW BEGINS TO MOVE INLAND AND OVER THE REGION. WITH THE LOW OFF NOW
TO THE EAST AND THE SEMI FORMED REX BLOCK TO THE WEST, NORTHERLY
FLOW WILL BEGIN TO DOMINATE OVER THE REGION. MODELS SHOW MUCH OF THE
PRECIPITATION TO BE TAPERING OFF WITH ONLY A FEW LINGERING SHOWERS
OVER THE CASCADES AND EASTERN MOUNTAINS. AS WE MOVE INTO THURSDAY,
DRIER CONDITIONS WILL BEGIN TO DOMINATE AND THE NORTH FLOW ALOFT
WILL USHER IN COLDER AIR. IN COULD CALCULATIONS SHOW THAT
TEMPERATURES WILL BE ANYWHERE FROM 10-20 DEGREES BELOW SEASONAL
AVERAGE WITH EFI IN AGREEMENT. TEMPERATURES THURSDAY AND THROUGH THE
WEEKEND WILL BE IN THE LOW TO MID 50S ACROSS A VAST MAJORITY OF THE
REGION WITH 70-80% PROBABILITIES AND ISOLATED 60S IN THE BASIN.
MODELS SHOW THIS PATTERN TO PERSIST THROUGH SUNDAY NIGHT AHEAD OF
ANOTHER PATTERN SHIFT. 90
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
CONDITIONS RANGE FROM VFR (MOST AREAS) TO MVFR AND EVEN SOME IFR
ACROSS THE REGION AS LOW PRESSURE AND RAIN IMPACT THE AREA. IF
RAIN IS HEAVY OR STEADY OR ENOUGH, THEN LOWERED CIGS AND/OR
VSBYS HAVE BEEN THE RESULT.
EXPECT THESE CONDITIONS TO REMAIN THROUGH THE DAY BEFORE
IMPROVEMENT TO VFR OCCURS EVERYWHERE THIS EVENING.
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
AERIAL FLOOD WATCHES ARE IN EFFECT FOR THE NORTHERN AND
SOUTHERN BLUE MOUNTAINS AND THE NORTHER AND SOUTHERN BLUE
MOUNTAIN FOOTHILLS THROUGH THURSDAY MORNING. UMATILLA AT
PENDLETON AND GIBBON IS EXPECTED TO REACH MINOR FLOOD STAGE
THURSDAY, JOHN DAY AT SERVICE CREEK, WALLA WALL NEAR TOUCHET,
NACHES NEAR CLIFFDELL AND NACHES ARE ALL EXPECTED TO REACH
BANKFULL BY THURSDAY AS WELL. MODERATE TO HEAVY RAINS THROUGH
THE AREA THROUGH WEDNESDAY WILL CAUSE THESE RIVERS TO RISE. 90
PRELIMINARY POINT TEMPS/POPS
PDT 50 39 59 38 / 100 40 20 20
ALW 50 42 59 39 / 100 50 40 30
PSC 61 42 66 40 / 100 20 20 10
YKM 63 39 67 40 / 80 0 0 10
HRI 55 40 64 39 / 100 20 10 10
ELN 56 39 60 35 / 80 0 0 10
RDM 51 26 62 29 / 60 10 0 0
LGD 45 36 54 35 / 100 90 30 50
GCD 45 31 56 32 / 100 80 0 10
DLS 57 41 66 42 / 80 10 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...90
AVIATION...77
HYDROLOGY...90
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