219
FXUS66 KPDT 120429 AAD
AFDPDT
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
929 PM PDT SAT APR 11 2026
KEY MESSAGES
- SHOWER AND THUNDERSTORM CHANCES CONTINUE TODAY, AND DECREASED
CHANCES ON SUNDAY.
- ANOTHER SYSTEM WILL BRING PRECIPITATION BACK TO THE REGION
LATER TUESDAY INTO WEDNESDAY.
DISCUSSION
AN UPPER LOW WAS APPROACHING NORTHERN CALIFORNIA AND WILL MOVE
INLAND EARLY SUNDAY MORNING. THE LOW WILL THEN WEAKEN AND MOVE
EAST NORTHEASTWARD THROUGH MONDAY AS A BROAD UPPER TROUGH
REMAINS OVER THE WESTERN CONUS. BY LATER MONDAY, INTO TUESDAY,
THIS TROUGH WILL MOVE EASTWARD AND WEAK RIDGING WILL MOVE INTO
THE AREA, FOLLOWED BY A MORE ZONAL WESTERLY FLOW.
GUIDANCE HAS CONTINUED TO SHOW THAT THE BEST CHANCES FOR
THUNDERSTORMS THIS AFTERNOON AND EVENING IS ALONG A DIAGONAL
LINE FROM CENTRAL OREGON THROUGH THE BLUE MOUNTAIN FOOTHILLS AND
INTO EASTERN OREGON. LATEST SATELLITE IMAGERY SHOWED SOME
CUMULUS FIELD DEVELOPMENT AND A LOT OF CLOUDS BUT ALSO ENOUGH
BREAKS IN THE CLOUDS FOR THUNDERSTORMS TO DEVELOP. THERE IS
CERTAINLY ENOUGH CAPE (200-500 J/KG) AND SUPPORTIVE LIS
(-1 TO -3 DEGREES CELSIUS). HOWEVER, TEMPERATURES ARE COOLER
THAN THEY WERE AT THIS TIME YESTERDAY AND SO FAR THUNDERSTORMS
HAVE STRUGGLED.
ANY THUNDERSTORMS SHOULD DECREASE THIS EVENING. ON SUNDAY, BOTH
THE SHOWER AND MORE LIMITED THUNDERSTORM THREAT WILL MOVE
EASTWARD AND MAINLY BE CONFINED TO EASTERN PORTIONS OF THE
AREA.
DRYING WILL MOVE IN FROM WEST TO EAST ON MONDAY AND CONTINUE
INTO MOST OF TUESDAY.
BY LATER TUESDAY INTO WEDNESDAY, AN AREA OF LOW PRESSURE WILL
DROP DOWN FROM CANADA AND BRING ANOTHER CHANCE OF PRECIPITATION,
INCLUDING THE POTENTIAL FOR LATE SEASON SNOW TO THE MOUNTAINS.
THIS NEXT SYSTEM LOOKS TO BEING OVER 0.75 INCHES OF LIQUID
EQUIVALENT QPF TO THE MOUNTAIN CRESTS AND AT LEAST SOME SNOW.
IT IS VERY DIFFICULT FOR SNOW TO ACCUMULATE DURING THE DAY THIS
TIME OF THE YEAR, BUT CERTAINLY IT CAN HAPPEN AT NIGHT, BUT AT
LEAST SEVERAL INCHES OF SNOW IS POSSIBLE, AND SNOW LEVELS WILL
BE BELOW PASS LEVEL. AT LOWER ELEVATIONS, GENERALLY 0.25 INCHES
OF RAIN OR LESS IS EXPECTED.
TEMPERATURES WILL AVERAGE ABOUT 5 DEGREES BELOW NORMAL WEDNESDAY
INTO THURSDAY, AND THERE COULD BE SOME BELOW FREEZING MORNINGS
ESPECIALLY IN THE COLDER VALLEYS. NBM PROBABILITIES ARE AS HIGH
AS 80-90 PERCENT FOR LOWS <=32 DEGREES THURSDAY MORNING IN THE
YAKIMA AND KITTITAS VALLEYS.
DRIER WEATHER IS THEN EXPECTED FOR THE END OF THE WEEK.
IT WILL ALSO BE A BIT BREEZY TUESDAY AND WEDNESDAY MAINLY IN THE
NORMALLY BREEZY LOCATIONS, WITH WIND GUSTS OF 30 TO 35 MPH, AND
POSSIBLY AS HIGH AS 40 MPH. NBM PROBABILITIES OF WIND GUSTS
>=39 MPH ARE BETWEEN 60 AND 80 PERCENT, ESPECIALLY ACROSS
PORTIONS OF THE COLUMBIA BASIN AND FOOTHILLS OF THE SOUTHERN
BLUE MOUNTAINS.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ANOTHER ROUND OF PRECIPITATION FOR THE AREA SPREADING SOUTH TO
NORTH ASSOCIATED WITH THE COLD/MOIST CONVEYOR BELT AND WEAK
ISENTROPIC LIFT FROM AND APPROACH LOW PRESSURE OFF THE PACIFIC.
VFR CONDITIONS ARE ANTICIPATED ALTHOUGH BRIEF MVFR VISIBILITY
AND CIGS CAN OCCUR ON SUNDAY IN RAIN. PRIMARY TIME WINDOW IS
FROM AROUND 14Z THROUGH 23Z, AND HIGH ENOUGH CONFIDENCE
(GREATER THAN 50 AND UPWARDS TO 80%) FOR USING PREVAILING RAIN.
PRELIMINARY POINT TEMPS/POPS
PDT 65 43 58 44 / 50 30 80 80
ALW 65 46 60 46 / 50 20 80 80
PSC 71 44 66 47 / 30 10 50 60
YKM 67 42 67 44 / 40 0 30 20
HRI 69 43 62 45 / 30 20 70 70
ELN 61 38 64 43 / 50 10 20 20
RDM 61 37 52 35 / 70 60 80 70
LGD 62 41 55 41 / 80 50 90 90
GCD 61 40 51 37 / 50 80 90 90
DLS 68 47 62 46 / 60 20 60 50
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...77
AVIATION...71
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