719
FXUS66 KPDT 111805
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1005 AM PST THU DEC 11 2025
UPDATED FOR AVIATION
AVIATION
18Z TAFS...VFR CONDITIONS ARE EXPECTED AT ALL TAF SITS, WITH MVFR
OR LOWER POSSIBLE AT DLS THOUGH CONFIDENCE IS BELOW AVERAGE (<40
PERCENT).
LINGERING GUSTY WINDS 20 TO 25 KTS WILL GRADUALLY DECREASE TO 10
KTS OR LESS AT ALL TAF SITES.
PREV DISCUSSION
/ISSUED 344 AM PST THU DEC 11 2025/
DISCUSSION...
KEY MESSAGES:
1. FLOODING CONCERNS PERSIST DUE TO CONTINUED MOUNTAIN RAIN.
*FLOOD WARNINGS & ADVISORIES ACTIVE*
2. WINDY CONDITIONS LINGER THROUGH THE MORNING.
*HIGH WIND WARNING & ADVISORIES ACTIVE*
3. ABOVE NORMAL TEMPERATURES UNTIL NEXT SYSTEM EARLY NEXT WEEK.
CURRENT RADAR AND INFRARED SATELLITE IMAGERY SHOWING LIGHT TO
MODERATE RETURNS ALONG THE WASHINGTON CASCADES UNDER PARTLY TO
MOSTLY CLOUDY SKIES. THIS IS IN RESPONSE TO AN UPPER LEVEL
SHORTWAVE AND COLD FRONT THAT WILL STALL OVER THE
WASHINGTON/OREGON BORDER TODAY BEFORE LIFTING NORTH THIS EVENING.
A STRONG ATMOSPHERIC RIVER (AR) HAS BEEN ASSOCIATED WITH THIS
SYSTEM, WHICH HAS DUMPED 2 TO 6 INCHES OF RAINFALL OVER THE
WASHINGTON CASCADES AND 1 TO 4 INCHES OF RAIN OVER THE NORTHERN
BLUE MOUNTAINS OVER THE LAST 48 HOURS. EVEN LOWER ELEVATIONS OF
THE COLUMBIA BASIN AND BLUE MOUNTAIN FOOTHILLS HAVE RECEIVED
0.25-0.75" OVER THE LAST 48 HOURS, WITH SOME STATIONS EARLIER IN
THE WEEK BREAKING DAILY PRECIPITATION RECORDS. THE AR WILL BE
LOSING STRENGTH THROUGH THE DAY TODAY BEFORE BEING CUT OFF LATER
THIS EVENING. AN ADDITIONAL INCH OF RAIN WILL BE POSSIBLE TODAY
ACROSS HIGHER TERRAIN OF THE CASCADE AND NORTHERN BLUE MOUNTAINS,
WITH AROUND 0.25" FOR LOWER SLOPES OF THE CASCADES, AND 0.02-0.10"
ALONG THE EAST SLOPES OF THE CASCADES (KITTITAS/SIMCOE HIGHLANDS)
AND THE NORTHERN BLUE MOUNTAIN FOOTHILLS.
DUE TO THE RAINFALL EARLIER IN THE WEEK, FLOODING CONCERNS ARE
ONGOING ALONG THE YAKIMA AND NACHES RIVERS AS SEVERAL REACHES ARE
CURRENTLY IN MODERATE FLOOD STAGE. THESE INCLUDE THE NACHES RIVER
AT NACHES AND THE YAKIMA RIVER AT HORLICK AND PARKER, WITH THE
REACH NEAR KIONA FORECAST TO REACH MODERATE FLOOD STAGE DURING
THE EARLY MORNING HOURS ON FRIDAY. OTHER REACHES ARE CURRENTLY IN
MINOR FLOOD STAGE, INCLUDING THE NACHES RIVER NEAR CLIFFDELL AND
THE YAKIMA RIVER AT EASTON AND UMTANUM. THE UPSTREAM REACHES HAVE
CRESTED AND ARE BEGINNING TO SLOWLY DECLINE IN RIVER LEVEL,
HOWEVER, THE YAKIMA RIVER AT UMTANUM, PARKER, AND KIONA ARE
CONTINUING TO RISE. THE REACHES NEAR UMTANUM AND PARKER ARE
FORECAST TO CREST LATER TODAY, WITH KIONA CRESTING FRIDAY
AFTERNOON THROUGH SATURDAY MORNING AT 15.59 FEET, 4 FEET HIGHER
THAN ITS CURRENT LEVEL (11.66 FEET AS OF 1:15 AM).
THE INCOMING COLD FRONT PUSHING INTO THE REGION HAS ALLOWED A
PRESSURE GRADIENT TO DEVELOP ACROSS THE COLUMBIA BASIN. THE RAP,
GFS, NAM, AND SREF ALL ADVERTISE A GRADIENT OF 9 TO 12 MB BETWEEN
PORTLAND (PDX) AND SPOKANE (GEG), WHICH RELATES TO SUSTAINED
SOUTHWEST WINDS OF 20 TO 40 MPH AND WIND GUSTS OF OF BETWEEN 55 TO
70 MPH. THESE HIGHER WIND VALUES ARE FOCUSED ACROSS THE LOWER
COLUMBIA BASIN OF WASHINGTON WHICH INCLUDES THE TRI-CITIES AREA.
GUSTS OF 67 MPH HAVE ALREADY BEEN OBSERVED THIS MORNING, WITH THE
POTENTIAL OF THESE HIGH WINDS LINGERING THROUGH THE EARLY
MORNING. THUS, A HIGH WIND WARNING IS CURRENTLY ACTIVE UNTIL 7 AM.
ELEVATED WINDS ARE ALSO OCCURRING ACROSS OTHER PORTIONS OF THE
COLUMBIA BASIN AND BLUE MOUNTAIN FOOTHILLS AS GUSTS OF 50-55 MPH
HAVE BEEN OBSERVED THIS MORNING AND WILL ALSO LINGER THROUGH THE
EARLY MORNING HOURS. AS A RESULT OF THE WINDY CONDITIONS, A WIND
ADVISORY IS CURRENTLY ACTIVE THROUGH 7 AM FOR NORTH-CENTRAL
OREGON, LOWER COLUMBIA BASIN OF OREGON, YAKIMA VALLEY, AND THE
NORTHERN/SOUTHERN BLUE MOUNTAINS.
THE COLD FRONT WILL BE RETREATING NORTH TONIGHT AND DEPARTS EAST
INTO THE WEEKEND AS AN UPPER LEVEL RIDGE BUILDS OFFSHORE AND
PASSES OVER THE AREA ON SATURDAY. THIS WILL KEEP CONDITIONS DRY
AND TEMPERATURES WELL ABOVE NORMAL AS HIGHS PEAK IN THE MID-TO
UPPER 50S ACROSS THE COLUMBIA BASIN AND IN THE LOW 60S OVER
CENTRAL OREGON. ENSEMBLES ARE IN FAIRLY GOOD AGREEMENT REGARDING
THE NEXT SYSTEM EARLY IN THE WEEK BRINGING WIDESPREAD RAINFALL
AND SLIGHTLY COOLER TEMPERATURES. MID-WEEK HIGH TEMPERATURES ARE
STILL EXPECTED TO BE 5 TO 10 DEGREES ABOVE NORMAL FOR THIS TIME OF
YEAR ACROSS THE COLUMBIA BASIN, WITH SNOW LEVELS LIKELY DROPPING
TO BETWEEN 3000-5000 FEET ON TUESDAY AND WEDNESDAY. THIS WILL
PROVIDE SOME SIGNIFICANT SNOWFALL ACROSS THE CASCADE AND NORTHERN
BLUE MOUNTAINS ABOVE 4000. ENSEMBLES DO STRUGGLE WITH THE STRENGTH
AND TIMING OF THE SYSTEM, WITH 23% OF MEMBERS HINTING AT LESS
SNOWFALL OVER THE CASCADES AND 22% SUGGESTING MORE. THE REMAINING
55% OF MEMBERS ARE ALIGNING WITH THE CURRENT FORECAST OF 10-20
INCHES OF SNOWFALL OVER THE CASCADE PASSES TUESDAY THROUGH
WEDNESDAY AND 5-15 INCHES OVER THE NORTHERN BLUE MOUNTAINS.
CONFIDENCE IN THESE AMOUNTS IS CURRENTLY LOW (10-30%) AS
UNCERTAINTY RESIDES PRIMARILY IN OVERALL SYSTEM STRENGTH. STAY
TUNED. 75
AVIATION...12Z TAFS...CURRENTLY, ALL SITES ARE IN VFR. HOWEVER,
KDLS MAY SEE MVFR CONDITIONS THIS MORNING INTO AFTERNOON HOURS FROM
LOW CLOUDS WITH THE INFLUENCE OF THE ONGOING ATMOSPHERIC RIVER.
KYKM/KALW COULD ALSO HAVE LIGHT RAIN DEVELOP IN THE MORNING HOURS AS
WELL, BUT CHANCES ARE LOW (<30%). OTHER THAN THAT, THE MAIN CONCERN
FOR MOST SITES WILL BE GUSTY WINDS UP TO 20-30KTS OR HIGHER THROUGH
LATER THIS MORNING. AN AIRPORT WEATHER WARNING FOR KPSC WILL REMAIN
THROUGH 6AM THIS MORNING DUE TO WINDS GUSTS POTENTIALLY EXCEEDING TO
40-50KTS. WITH KBDN SEEING GUSTS AT 25KTS AROUND THIS EARLY MORNING,
THERE IS A SLIGHT CHANCE THAT KRDM MIGHT SEE SOME GUSTS ALONG WITH
KBDN (30% CHANCE). FEASTER/97
PRELIMINARY POINT TEMPS/POPS
PDT 59 43 60 39 / 30 20 0 0
ALW 59 49 59 44 / 50 30 10 10
PSC 62 44 59 39 / 20 10 0 0
YKM 57 42 57 37 / 30 20 0 0
HRI 61 44 59 38 / 20 10 0 0
ELN 51 40 53 36 / 60 30 10 10
RDM 58 30 60 29 / 0 0 0 0
LGD 54 41 57 36 / 40 20 10 0
GCD 55 36 57 35 / 0 0 0 0
DLS 61 47 59 41 / 60 30 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...FLOOD WATCH THROUGH FRIDAY MORNING FOR WAZ026-027-521>523.
SHORT TERM...75
LONG TERM....75
AVIATION...77
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