256
FXUS66 KPDT 171736
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
936 AM PST WED DEC 17 2025
UPDATED AVIATION
PREV DISCUSSION
/ISSUED 415 AM PST WED DEC 17 2025/
DISCUSSION...CURRENT SATELLITE AND RADAR IMAGERY SHOW LIGHT SHOWERS
ACROSS THE FORECAST AREA WITH THE LOWER COLUMBIA BASIN AND PORTIONS
OF THE FOOTHILLS OF THE NORTHERN BLUES-OR HAVING LOCALLY MODERATE
RAINFALL WITH SPORADIC LIGHTNING.
THANKS TO THE UPPER SHORTWAVE AND PERSISTENT ATMOSPHERIC RIVER, THIS
WILL HELP INFLUENCE IN DEVELOPING LOW-TOPPED CONVECTION WITH THE
FRONTAL SYSTEM MAINLY OVER THE EASTERN MOUNTAINS DURING THE EARLY
MORNING HOURS. THIS ALSO PUTS THAT AREA IN THE MARGINAL RISK OF
SEVERE THUNDERSTORMS, ACCORDING TO THE STORM PREDICTION CENTER
(SPC). THE 00Z HREF GUIDANCE SUGGESTS A 10-20% PROBABILITY FOR
THUNDER OVER THE EASTERN MOUNTAINS EARLY THIS MORNING. ALSO, THE
CAMS SEEM TO FAVOR A 30-50% PROB FOR THUNDERSTORMS ACROSS THE
AFOREMENTIONED AREA WITH THE MODELS (GFS, RAP, NAM) SHOWING SCANT
INSTABILITY. THAT SAID, THIS MAY BE ENOUGH TO POTENTIALLY SUPPORT
SPORADIC/SUB-SEVERE STORMS WITH SCANT LIGHTING FLASHES.
IN ADDITION TO THE SHORTWAVE AND ATMOSPHERIC RIVER, THIS HIGH WIND
EVENT WILL CONTINUE THROUGH THIS AFTERNOON ACROSS MOST OF THE
FORECAST AREA. THIS WILL REMAIN DRIVEN BY THE STRONG LOW-LEVEL JET
STREAK OF 50-100 KTS ALONG WITH A SURFACE PRESSURE DIFFERENCE OF 10-
20 MB BETWEEN PDX (PORTLAND) AND GEG (SPOKANE). HIGH WIND WARNINGS
(FROM COLUMBIA BASIN TO CENTRAL OR) AND A WIND ADVISORY (FROM JOHN
DAY BASIN, GRAND RONDE VALLEY AND WALLOWAS) WILL REMAIN EFFECTIVE
THROUGH THIS AFTERNOON. STRONGEST WIND GUSTS OF 55-65 MPH ARE
EXPECTED ALONG PORTIONS OF THE BLUE MOUNTAIN FOOTHILLS AND SLOPES OF
THE NORTHERN BLUE MOUNTAINS. BY LATE THIS AFTERNOON, WINDS WILL THEN
SLOWLY DECREASE WITH LINGERING BREEZY WINDS OVER THE SIMCOE
HIGHLANDS AND PORTIONS OF THE NORTHWEST BLUES. WE MIGHT SEE WINDY
CONDITIONS RETURN THURSDAY AFTERNOON THROUGH FRIDAY MORNING WITH
GUSTS UP TO 35-45 MPH ACROSS MAJORITY OF THE FORECAST AREA.
STRONGEST WINDS OF 55-65 MPH WILL BE OVER THE CREST OF OR CASCADES
AND HIGHER TERRAINS OF CENTRAL OR LATE THURSDAY EVENING INTO
OVERNIGHT HOURS WITH A SLIGHT CHANCE (<30%) OF GUSTS AT 70 MPH.
TONIGHT THROUGH FRIDAY, MOUNTAIN SNOW WILL DEVELOP AS WIDESPREAD
PRECIPITATION CONTINUES DUE TO THE ATMOSPHERIC RIVER MOVING ACROSS
THE PACIFIC NORTHWEST. THERE IS POTENTIAL FOR LOW-ELEVATION SNOWFALL
WITH HIGH CHANCES (>70 PERCENT) IN THE GRANDE RONDE VALLEY AND JOHN
DAY BASIN, BUT SNOW LEVELS WILL RISE ABOVE 3 KFT IN THOSE LOW-
ELEVATION AREAS THURSDAY MORNING ONWARD IN THE WAKE OF A WARM
FRONTAL SYSTEM, LIMITING DURATION OF SNOWFALL. HOWEVER, THE WA
CASCADES WILL LIKELY SEE ADDITIONAL SNOWFALL UP TO 1 INCH THROUGH
WEDNESDAY NIGHT INTO THURSDAY WITH A MODERATE CHANCE (50-60%) FOR
BLOWING SNOW.
RIVER FLOOD WATCHES AND FLOOD WATCHES REMAIN IN EFFECT DUE TO
ANTICIPATED RISING RIVER LEVELS THROUGH THE WEEK. FEASTER/97
AVIATION...18Z TAFS...WINDS WILL REMAIN THE PRIMARY CONCERN
THROUGH THE FORECAST PERIOD AS MULTIPLE TAF SITES WILL CONTINUE
TO SEE ELEVATED WINDS. PDT/ALW/PSC ARE STILL SEEING WINDS OF
20-25KTS SUSTAINED WITH GUSTS UP TO NEAR 40KTS. VFR CONDITIONS
WILL PERSIST THROUGH THE PERIOD WITH RDM BEING THE ONLY SITE TO
SEE MVFR THROUGH 00Z DUE TO LOW CIGS OF 2500FT. WINDS ARE EXPECTED
TO BEGIN TAPERING OFF AFTER 00Z AS THE FRONT WILL HAVE MOVED
PAST. 90
PRELIMINARY POINT TEMPS/POPS
PDT 53 36 55 39 / 50 20 100 90
ALW 53 39 55 41 / 70 10 100 90
PSC 56 38 51 40 / 20 10 100 80
YKM 49 34 45 31 / 30 30 100 80
HRI 55 38 54 39 / 20 20 100 90
ELN 43 30 40 26 / 60 40 100 80
RDM 45 29 57 37 / 50 50 100 90
LGD 51 31 45 37 / 100 20 100 100
GCD 51 30 50 41 / 90 50 100 90
DLS 50 38 48 40 / 70 70 100 100
PDT WATCHES/WARNINGS/ADVISORIES
OR...HIGH WIND WARNING UNTIL 4 PM PST THIS AFTERNOON FOR ORZ041-044-
507-508-510-511.
WIND ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR ORZ049-050-505.
WINTER WEATHER ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR ORZ509.
WA...HIGH WIND WARNING UNTIL 4 PM PST THIS AFTERNOON FOR WAZ024-
026>029-521.
FLOOD WATCH THROUGH FRIDAY AFTERNOON FOR WAZ522-523.
WINTER WEATHER ADVISORY UNTIL 10 PM PST THIS EVENING FOR WAZ522-
523.
SHORT TERM...97
LONG TERM....97
AVIATION...90
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