904
FXUS02 KWBC 280748
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
348 AM EDT SUN SEP 28 2025
VALID 12Z WED OCT 01 2025 - 12Z SUN OCT 05 2025
...TROPICAL DEPRESSION NINE WILL BRING TROPICAL IMPACTS TO THE
SOUTHEAST/CAROLINAS NEXT WEEK...
..OVERVIEW
UNCERTAINTY REMAINS AROUND THE TRACK OF TROPICAL DEPRESSION NINE,
BUT THE GENERAL TREND HAS FAVORED A SLOWER PROGRESSION AND CURVING
EASTWARD BEFORE REACHING THE CAROLINAS. THE CURRENT FORECAST TRACK
SHOWS NINE STALLING JUST OFFSHORE IN THE WESTERN ATLANTIC BUT
PROVIDING RAIN AND POSSIBLE FLOODING TO AT LEAST THE COASTAL
CAROLINAS FOR THE START OF THE MEDIUM RANGE PERIOD DURING THE SHORT
RANGE THAT MAY BLEED OVER INTO THE VARY START OF THE MEDIUM RANGE
PERIOD. THE TRACK OF HUMBERTO LOCATED FURTHER EAST OVER THE
ATLANTIC WILL INFLUENCE THE BEHAVIOR OF NINE, ALONG WITH COOL
SURFACE HIGH PRESSURE OF THE NORTHEAST AND A NORTHERN STREAM
TROUGH, WHICH WILL AFFECT HOW FAR INLAND BANDS OF HEAVIER RAIN AND
WIND GUSTS MAY REACH.
FARTHER WEST, MEAN UPPER RIDGING IS FORECAST TO SET UP FROM THE
SOUTHWEST NORTHEASTWARD INTO THE MIDWEST PROMOTING WARM
TEMPERATURES AND MAINLY DRY CONDITIONS. MEANWHILE THE WEST CAN
EXPECT MEAN TROUGHING WITH COOLER TEMPERATURES AND ROUNDS OF
PRECIPITATION.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LARGE SCALE PATTERN IS IN FAIRLY DECENT AGREEMENT WITH THE
DEPICTION OF A MEAN UPPER TROUGH WITH MULTIPLE IMPULSES EXITING
THROUGH THE WEST, RIDGING OVER PARTS OF CENTRAL CONUS, WITH UPPER
TROUGHING OVER THE NORTHEAST AND TROPICAL SYSTEM NEAR THE
SOUTHEAST; WITH THE GREATEST UNCERTAINTY WITH THE EVOLUTION OF
TROPICAL CYCLONE NINE. THERE CONTINUES TO BE SOME RUNS FAVORING
THE CYCLONE TO TURN EAST FASTER WHILE OTHERS SLOW DOWN ITS
PROGRESSION. CONTINUE TO MONITOR NHC FORECASTS FOR FURTHER DETAILS
AND UPDATES TO THE TRACK AND TIMING OF NINE.
FOR THE WPC FORECAST, USED THE ECMWF/EC ENSEMBLE/AIFS THROUGH THE
END OF THE WEEK FOR QPF AND BACKGROUND MODEL DATA WITH THE NHC
POINTS FOR THE SYSTEM. ELSEWHERE, MODELS ARE GENERALLY AGREEABLE ON
THE LARGE SCALE WITH THE MEAN TROUGH IN THE WEST SLOWLY MOVING
EASTWARD WITH LESS CERTAIN SHORTWAVES MOVING THROUGH AND PUSHING
FRONTS THROUGH THE REGION, BUT THE SPREAD IS TYPICAL FOR THE MEDIUM
RANGE TIME FRAME. CONSENSUS FOR AN ELONGATED UPPER RIDGE SPANNING FROM
THE SOUTHWEST TO THE CENTRAL U.S. INTO THE OHIO VALLEY AND
EVENTUALLY THE NORTHEAST. WEAK ENERGY MAY CUT OFF FROM THIS RIDGE
IN THE SOUTHERN STREAM OVER THE SOUTHEAST OR SO, WITH MORE
UNCERTAINTY. OVERALL ACROSS THE LOWER 48, A MULTI- MODEL BLEND OF
MAINLY DETERMINISTIC GUIDANCE WAS USED FOR THE EARLY TO MID MEDIUM
RANGE PERIOD, WITH INCREASING PROPORTIONS OF THE GEFS AND EC
ENSEMBLE MEANS DURING THE LATTER PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
WET AND UNSETTLED CONDITIONS CAN BE EXPECTED FOR PORTIONS OF THE
SOUTHEAST/CAROLINAS AS ANOMALOUSLY HIGH TROPICAL MOISTURE STREAMS
NORTHWARD AND ITS INTERACTION WITH A LINGERING STATIONARY FRONT.
HEAVY RAIN AND FLASH FLOODING ARE THREATS WITH THIS SYSTEM NOW ARE
LARGELY IN THE SHORT RANGE PERIOD, HOWEVER COASTAL AREAS WILL
LIKELY CONTINUE TO HAVE SOME HIGHER INTENSITY RAINFALL INITIALLY.
IT IS MORE UNCERTAIN HOW MUCH RAIN WILL REACH FARTHER INLAND. GIVEN
THE LATEST NHC TRACK FOR NINE FOR THE MEDIUM RANGE PERIOD, THE BULK
OF THE RAINFALL WILL KEEP OFFSHORE THUS PRESENTING A DECREASED
THREAT FOR EXCESSIVE RAINFALL. THERE ARE NO AREAS HIGHLIGHTED FOR
EXCESSIVE RAINFALL POTENTIAL, HOWEVER THIS MAY CHANGE IF NHC BEGINS
TO BRING NINE FURTHER NORTH AGAIN. SCATTERED SHOWERS AND STORMS
ARE POSSIBLE IN FLORIDA AND INTO THE GULF COAST THROUGH MUCH OF THE
WEEK.
A WEAK ATMOSPHERIC RIVER IS FORECAST TO PUSH ACROSS THE PACIFIC
NORTHWEST INTO CALIFORNIA ON TUESDAY AND WEDNESDAY WITH A COLD
FRONT AHEAD OF THE UPPER TROUGH. RAIN TOTALS GENERALLY UNDER AN
INCH OR TWO DO NOT APPEAR TO CAUSE HAZARDOUS CONDITIONS IN THE
COASTAL MOUNTAIN AREAS THAT ARE ACCUSTOMED TO SEEING MULTIPLE
INCHES OF RAIN. RAIN COULD CONTINUE IN THE WEST COAST STATES
THROUGH THURSDAY WITH ANOTHER FRONT. ROUNDS OF PRECIPITATION WILL
BE LIKELY ACROSS PARTS OF THE INTERMOUNTAIN WEST/ROCKIES THROUGH
MULTIPLE DAYS NEXT WEEK, AND THE HIGHER ELEVATIONS CAN EXPECT SNOW.
PRECIPITATION CHANCES MAY ALSO INCREASE LATER NEXT WEEK ACROSS THE
NORTH-CENTRAL U.S. ONCE THE FRONTAL SYSTEM PUSHES ACROSS THE
MOUNTAIN AND EMERGES IN THE PLAINS.
WITH UPPER RIDGING BUILDING OVERHEAD, WARMER THAN SEASONAL AVERAGE
TEMPERATURES ARE EXPECTED ACROSS THE CENTRAL U.S., ESPECIALLY FOR
THE NORTHERN PLAINS TO UPPER MIDWEST. HIGHS OF 10 TO 20 DEGREES
ABOVE NORMAL WILL BE COMMON IN THOSE AREAS, WITH HIGHS OF 80F
REACHING TO THE CANADIAN BORDER BY WEDNESDAY. 90S ARE LIKELY TO
CONTINUE FOR EARLY OCTOBER INTO THE DESERT SOUTHWEST AND TEXAS.
MEANWHILE, BELOW NORMAL TEMPERATURES ESPECIALLY FOR HIGHS ARE
LIKELY ACROSS THE WEST DUE TO UPPER TROUGHING AND RAINY/CLOUDY
CONDITIONS.
CAMPBELL/TATE
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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