958
FXUS66 KPDT 192142
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
242 PM PDT MON MAY 19 2025
SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT
A FAST MOVING
SHORTWAVE IS RAPIDLY CROSSING THE AREA THIS AFTERNOON. SATELLITE
AND RADAR SHOW THE BACK EDGE OF THE MAIN BAND OF PRECIPITATION IS
MOVING INTO THE BLUE MOUNTAINS AND SHOULD MOVE OUT OF WALLOWA
COUNTY IN THE LATE AFTERNOON. BEHIND THE FRONT, SKIES ARE
CLEARING AND DAYTIME HEATING IS DEVELOPING SOME WAVE AND CUMULUS
CLOUDS. THERE IS ENOUGH INSTABILITY (100-400 J/KG) FOR SOME
SHOWERS AND PERHAPS AN ISOLATED THUNDERSTORM OR TWO THROUGH
SUNDOWN THOUGH CHANCES AREN'T LOOKING TOO PROMISING BASED ON
CURRENT WEBCAMS AND RADAR. BREEZY WINDS CONTINUE OVER MUCH OF THE
AREA WITH WEST TO NORTHWEST WINDS OF 15 TO 25 MPH WITH GUSTS TO
35 MPH. THIS SHOULD WIND DOWN THIS EVENING THOUGH THE BLUE
MOUNTAIN FOOTHILLS WILL CONTINUE TO HAVE SOUTHWEST WINDS OF 10 TO
15 MPH OVERNIGHT. WITH PARTIAL CLEARING, LOWS TONIGHT WILL BE A
FEW DEGREES COOLER THOUGH LINGERING CLOUDS OVER THE MOUNTAINS
SHOULD KEEP MOST AREAS ABOVE FREEZING.
BEHIND THE DEPARTING SHORTWAVE, AN UPPER LOW OFF THE NORTHERN
BRITISH COLUMBIA COAST WILL KEEP A ZONAL WEST TO NORTHWEST FLOW
OVER THE AREA TOMORROW WHICH WILL REMAIN OVER THE AREA THROUGH
WEDNESDAY WITH SOME GRADUAL RIDGE BUILDING OVER TIME. THIS WILL
GIVE US QUIETER WEATHER WITH FEW CONCERNS. AN UPSLOPE FLOW INTO
THE MOUNTAINS MAY CREATE A SLIGHT CHANCE OF SHOWERS IN THE
MOUNTAINS TUESDAY THOUGH ANY PRECIPITATION AMOUNTS WILL BE JUST A
FEW HUNDREDTHS OF AN INCH AT MOST. TEMPERATURES WILL WARM A FEW
DEGREES EACH DAY WITH HIGHS IN THE 60S WITH 50S IN THE MOUNTAINS
TOMORROW THEN TO THE UPPER 60S TO LOWER 70S WITH LOWER TO MID 60S
IN THE MOUNTAINS ON WEDNESDAY. TUESDAY AFTERNOON WILL HAVE ANOTHER
ROUND OF BREEZY AFTERNOON WINDS OF 10 TO 20 MPH (15 TO 25 MPH
THROUGH THE COLUMBIA GAPS) WITH GUSTS OF 25 TO 35 MPH. WINDS
WILL BE MUCH LIGHTER WEDNESDAY.
WEDNESDAY NIGHT, MODELS SHOW A SHORTWAVE ARRIVING IN THE EVENING
AND PUSHING THE MODEST RIDGE OFF TO THE EAST. A SLIGHT CHANCE OF
LIGHT SHOWERS WILL BEGIN IN CENTRAL OREGON DURING THE EVENING
THEN SPREAD A CHANCE OF RAIN ACROSS THE REST OF OREGON OVERNIGHT
WITH A SLIGHT CHANCE IN WASHINGTON. RAIN AMOUNTS WILL BE UP TO 5
HUNDREDTHS OF AN INCH MAINLY IN THE OCHOCO AND SOUTHERN BLUE
MOUNTAINS. PERRY/83
LONG TERM...THURSDAY THROUGH MONDAY
A ZONAL PATTERN WILL DOMINATE
THE PACNW THURSDAY WITH A SHORTWAVE TROUGH APPROACHING FRIDAY AND A
UPPER RIDGE BUILDING OVER SATURDAY ONWARDS. DETERMINISTIC MODELS MAY
BE ALIGNED TOGETHER WITH THESE PROGRESSIVE WAVE PATTERNS, BUT
DIFFERS ON TIMING FOR SATURDAY WHEN THE RIDGE MOVES ONSHORE. BOTH
GFS AND ECMWF SHOW THE RIDGE OVER THE FORECAST AREA WHEREAS CANADIAN
HAS A CYCLONIC LOW SWEEPING ACROSS. BEING SAID, THIS CAN CAUSE
DIFFICULTIES TO SPECIFY THE MAIN PATTERN FOR THIS TERM.
REGARDLESS, LIGHT SHOWERS WILL DEVELOP THROUGH NEXT WEEK WITH DRY
BREAKS DURING LATE AFTERNOON AND EVENING HOURS THURSDAY THROUGH
SATURDAY. SUNDAY INTO MONDAY IS WHEN POP CHANCE MAY SLIGHTLY
INCREASE ABOVE 20% DUE TO SHOWERS BECOMING MORE WIDESPREAD. AND
GIVEN THE INFLUENCE OF THE SW ALOFT, THUNDERSTORMS MIGHT DEVELOP
SUNDAY NIGHT OVER THE JOHN DAY HIGHLANDS AND THEN RETURN MONDAY
ACROSS THE BLUES AND EASTERN MOUNTAINS BUT CHANCES ARE LOW (<30%)
DUE TO WEAK INSTABILITY AND LOW MOISTURE. ALL MODELS DO SHOW
MOISTURE FOR MONDAY FROM A CERTAIN LEVEL WITH THE ECMWF MORE WETTER
THAN GFS AND CANADIAN, THANKS TO THE TROUGH SLIGHTLY CLIPPING FROM
THE BACKSIDE OF THE RIDGE. IF THE TROUGH WERE TO ARRIVE ONSHORE
SOONER, THUNDERSTORMS COULD FURTHER INTENSIFY ALONG WITH THE SW
ALOFT. FEASTER/97
AVIATION...18Z TAFS
ALL SITES WILL BE VFR THROUGHOUT THE DAY.
KDLS/KPDT/KYKM/KALW/KPSC WILL HAVE LIGHT SHOWERS DURING THIS MORNING
INTO EARLY AFTERNOON. GUSTY WINDS MAY DEVELOP AT 20-30 KTS WITH
SUSTAINED WINDS OF 12-20 KTS FOR MOST SITES THROUGHOUT TODAY, EXCEPT
FOR KALW. FEASTER/97
PRELIMINARY POINT TEMPS/POPS
PDT 43 65 41 69 / 30 10 0 0
ALW 45 64 43 67 / 30 20 10 0
PSC 44 69 41 72 / 10 0 0 0
YKM 40 68 38 69 / 0 10 0 0
HRI 45 69 41 72 / 10 0 0 0
ELN 39 63 39 67 / 10 10 0 0
RDM 34 62 31 70 / 0 0 0 0
LGD 40 58 35 66 / 60 20 0 0
GCD 37 61 34 70 / 20 10 0 0
DLS 46 66 43 71 / 20 10 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...83
LONG TERM....97
AVIATION...97
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