664
FXUS66 KPDT 252201
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
301 PM PDT SAT OCT 25 2025
DISCUSSION...TODAY THROUGH SUNDAY NIGHT
THE MAIN AREA OF LOW
PRESSURE ASSOCIATED WITH A BROAD UPPER TROUGH OVER THE PACIFIC
NORTHWEST CONTINUES TO CHURN OFFSHORE. MEANWHILE, SHOWERS AND
ISOLATED THUNDERSTORMS ARE ONGOING OVER THE FAR EASTERN COLUMBIA
BASIN, BLUE MOUNTAIN FOOTHILLS, AND BLUE MOUNTAINS. SPC'S
MESOSCALE ANALYSIS SUGGESTS MLCAPE OF UP TO 250 J/KG COUPLED WITH
EFFECTIVE SHEAR OF 35-45 KTS IS PRESENT OVER THE AFOREMENTIONED
AREA. A LINEAR SEGMENT DEVELOPED IN THE EASTERN COLUMBIA BASIN OF
OREGON AND IS TRACKING EAST-NORTHEAST OUT OF OUR FORECAST AREA.
OUTFLOW WINDS OF 45-55 MPH HAVE ACCOMPANIED THIS LINE. ELSEWHERE,
MORE ISOLATED THUNDERSTORMS HAVE PRODUCED SMALL HAIL (0.50 INCH
DIAMETER OR LESS).
SOUTHWEST TO WEST WINDS OF 25-35 MPH WITH GUSTS UP TO 55 MPH ARE
STILL LIKELY (80 PERCENT CONFIDENCE) ACROSS MOST OF THE LOWER
ELEVATIONS THIS AFTERNOON INTO THE OVERNIGHT HOURS. LOCATIONS
ESPECIALLY PRONE TO STRONG SOUTHWEST WINDS -- ESPECIALLY NORTH-
CENTRAL OREGON -- MAY SEE GUSTS UP TO 65 MPH (60 PERCENT
CONFIDENCE) THIS AFTERNOON AS A STRONG LOW-LEVEL JET OF 50-65 KTS
MIXES TO THE SURFACE.
SNOW LEVELS WILL CONTINUE TO FALL TO AROUND 4500 FT MSL THROUGH
LATE AFTERNOON. ONSET OF SNOWFALL AT PASS LEVEL IN THE OREGON AND
WASHINGTON CASCADES IS NOW EXPECTED BY 5-7 PM PDT SO HAVE MOVED
THE START TIME OF THE WINTER WEATHER ADVISORIES TO 5 PM PDT THIS
AFTERNOON. DESPITE NBM PROBABILITIES OF WARNING-LEVEL SNOW TOTALS
(8 INCHES OR GREATER) BEING HIGH (80 PERCENT) AT SANTIAM PASS,
HAVE OPTED TO RETAIN THE HEADLINE AS AN ADVISORY DUE TO THE LONG
DURATION OF THE EVENT, SHOWERY NATURE OF THE PRECIPITATION,
POTENTIAL FOR LOWER ACCUMULATION DURING THE DAYTIME HOURS THIS
AFTERNOON AND SUNDAY AFTERNOON, AND SOME LINGERING UNCERTAINTY IN
MESOSCALE DETAILS OF THE PATTERN AS THE NEXT SHORTWAVE ARRIVES
SUNDAY.
SUNDAY NIGHT THROUGH THURSDAY...CONFIDENCE IS MEDIUM-HIGH (60-80
PERCENT) IN A BREAK IN ACTIVE WEATHER FOR THE BULK OF THE FORECAST
AREA (NON-MOUNTAIN AREAS, ESPECIALLY EAST OF THE CASCADES) AS AN
UPPER-LEVEL RIDGE BUILDS INTO THE PACIFIC NORTHWEST. MOISTURE
TRANSPORT LOOKS TO BE MOSTLY DIRECTED INTO BRITISH COLUMBIA AND
WESTERN WASHINGTON.
FRIDAY ONWARD...ACTIVE WEATHER MAY RETURN (50 PERCENT CONFIDENCE)
AS ENSEMBLE CLUSTERS SUGGEST ROUGHLY EVEN ODDS OF AN ATMOSPHERIC
RIVER GETTING DIRECTED INTO THE REGION VERSUS STAYING NORTHWEST OF
THE FORECAST AREA.
MORNING UPDATE
AS OF 1715Z, SATELLITE IMAGERY SHOWS AN AREA OF
LOW PRESSURE CHURNING OFFSHORE, WITH TWO LOW CENTERS NOTED. A
COLD FRONTAL BOUNDARY IS PUSHING EASTWARD INTO THE CASCADES, WITH
WINDS EXPECTED TO RAMP ACROSS THE REGION THROUGH THE AFTERNOON AS
IT TRACKS INLAND AND A ROBUST LOW-LEVEL JET OVERSPREADS THE
REGION. CAMS CONTINUE TO SUGGEST A CONVECTIVE LINE WILL DEVELOP
ALONG THE FRONT BY 1-3 PM PDT THIS AFTERNOON ACROSS THE EASTERN
HALF OF THE COLUMBIA BASIN INTO THE BLUE MOUNTAINS. MADE SOME
MODIFICATIONS TO THE THUNDER FORECAST, AND NOTED GUSTY OUTFLOW
WINDS IN THE GRIDDED FORECAST. STRONGER SHOWERS AND/OR
THUNDERSTORMS WILL BE CAPABLE OF PRODUCING SEVERE WIND GUSTS (50
KTS OR GREATER) ACROSS THE AFOREMENTIONED REGION, AND SPC'S DAY 1
CONVECTIVE OUTLOOK HAS THE AREA IN A MARGINAL RISK WITH WIND AS
THE ONLY ANTICIPATED HAZARD.
REGARDING HEADLINES, BASED ON LATEST 12Z HREF GUIDANCE AND
OBSERVATIONAL TRENDS HAVE PUSHED UP THE ONSET TIMING OF WIND
ADVISORIES IN CENTRAL AND NORTH-CENTRAL OREGON AS WELL AS ALONG
THE FOOTHILLS OF THE BLUE MOUNTAINS AND LOWER COLUMBIA BASIN IN
OREGON.
AVIATION...18Z TAFS
VFR CONDITIONS WILL CARRY ON THROUGHOUT
THIS PERIOD, THOUGH MVFR CONDITIONS COULD OCCUR IF LOW CLOUD DECKS
FURTHER DEVELOPS. SHOWERS AND BREEZY TO WINDY CONDITIONS WILL
CONTINUE AS THE FRONTAL SYSTEM PASSES ACROSS OUR FORECAST AREA.
KPDT, KRDM, KBDN, KYKM, KALW AND KPSC WILL SEE SUSTAINED WINDS OF
15-25KT WITH GUSTS AT 25-35KTS STARTING THIS AFTERNOON THROUGH
OVERNIGHT. HOWEVER, WIND GUSTS MAY DECREASE LATE EVENING FOR
KRDM/KBDN. LLWS OF 23045KTS AT KALW AND 22045KTS AT KPSC AROUND
01Z. THESE CONDITIONS SHOULD DECREASE OVERNIGHT INTO SUNDAY
MORNING FOR THESE AFOREMENTIONED SITES, BUT KALW/KPSC MIGHT SEE AN
UPTICK IN WINDS UP TO 12KTS (<30% CHANCE). KDLS COULD HAVE WINDS
INCREASE TO 12KTS THIS EARLY AFTERNOON AS WELL, BUT WILL BECOME
LIGHT AROUND 02Z. FEASTER/97
PRELIMINARY POINT TEMPS/POPS
PDT 38 55 35 54 / 30 70 50 10
ALW 41 55 38 54 / 40 70 70 20
PSC 39 55 34 56 / 20 50 30 10
YKM 34 52 29 53 / 40 70 20 10
HRI 39 56 35 56 / 20 60 30 10
ELN 29 47 27 50 / 60 70 40 10
RDM 29 49 25 52 / 50 80 30 10
LGD 31 52 32 49 / 50 70 80 20
GCD 33 50 30 50 / 30 80 50 0
DLS 41 54 39 56 / 80 90 50 30
PDT WATCHES/WARNINGS/ADVISORIES
OR...WIND ADVISORY UNTIL 7 AM PDT SUNDAY FOR ORZ041.
WIND ADVISORY UNTIL 5 AM PDT SUNDAY FOR ORZ044-507.
WINTER WEATHER ADVISORY FROM 8 AM SUNDAY TO 8 AM PDT MONDAY FOR
ORZ502.
WIND ADVISORY UNTIL 2 AM PDT SUNDAY FOR ORZ508-510-511.
WINTER WEATHER ADVISORY UNTIL 2 AM PDT MONDAY FOR ORZ509.
WA...WIND ADVISORY UNTIL 7 AM PDT SUNDAY FOR WAZ024-027>029-521.
WINTER WEATHER ADVISORY FROM 8 AM SUNDAY TO 8 AM PDT MONDAY FOR
WAZ030.
WINTER WEATHER ADVISORY UNTIL 11 PM PDT SUNDAY FOR WAZ522.
DISCUSSION...86
MORNING UPDATE...86
AVIATION...97
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