815
FXUS02 KWBC 111955
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
355 PM EDT THU SEP 11 2025
VALID 12Z SUN SEP 14 2025 - 12Z THU SEP 18 2025
..OVERVIEW
ON SUNDAY, UPPER TROUGHING ATOP THE NORTHERN/CENTRAL ROCKIES WILL
SUPPORT DOWNSTREAM MOIST SOUTHERLY FLOW TO STREAM INTO THE PLAINS
AND CAUSE SOME MODERATE TO HEAVY RAIN. THIS TROUGH IS FORECAST TO
SLOWLY LIFT OUT EARLY NEXT WEEK WHILE ANOTHER TROUGH RELOADS IN THE
WEST TO SPREAD ENHANCED RAIN CHANCES FROM THE NORTHWEST/WEST TO
THE ROCKIES/PLAINS. TROUGHING IN THE EAST EARLY NEXT WEEK SHOWS
MORE UNCERTAINTY WITH ITS EVOLUTION, BUT MAY LEAVE A CLOSED UPPER
LOW BEHIND, WHICH ALONG WITH A FRONTAL SYSTEM OR TWO COULD CAUSE
RAIN CHANCES ALONG AT LEAST COASTAL AREAS OF THE EASTERN SEABOARD.
UPPER RIDGING IN BETWEEN THESE FEATURES SHOULD BRING ABOVE NORMAL
TEMPERATURES TO THE MISSISSIPPI VALLEY AND VICINITY, WITH SOME
AREAS WELL INTO THE 90S FOR HIGHS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS AND ENSEMBLES AGREE ON THE GENERAL TROUGH-RIDGE-TROUGH
PATTERN OVER THE LOWER 48 INTO SUNDAY, ALONG WITH THE ROCKIES
TROUGH LIFTING NORTHEAST BY MONDAY AND THE NEXT UPPER TROUGH
(POSSIBLE CLOSED LOW AT TIMES) TRAVERSING THE NORTHWEST EARLY NEXT
WEEK AND REACHING THE NORTH-CENTRAL CONUS MIDWEEK OR SO. FOR THE
LATTER FEATURE, THE 00Z CMC WAS A BIT FAST/EAST WITH THE FEATURE
BUT THE 12Z CMC CAME IN CLOSER TO CONSENSUS. MODEL GUIDANCE ALSO IS
AGREEABLE REGARDING AN UPPER RIDGE CENTERED OVER THE EAST-CENTRAL
U.S. BECOMING POSITIVELY TILTED. THE MOST UNCERTAIN PART OF THE
FORECAST IS THE EVOLUTION OF THE TROUGH IN THE EAST. RECENT 00/06Z
AND NEWER 12Z MODELS ARE NOW MORE AGREEABLE WITH THE NORTHERN
STREAM TROUGH MOVING EASTWARD THROUGH SOUTHEAST CANADA WITH LESS
DIGGING ENERGY INTO THE NORTHEAST THAN MOST MODELS SHOWED A DAY
AGO. THIS PROGRESSIVE FLOW IN THE NORTHERN STREAM ALLOWS FOR SOME
SOUTHERN STREAM TROUGHING TO BE LEFT BEHIND IN THE SOUTHEAST/MID-
ATLANTIC WITH A WEAK CLOSED LOW AT TIMES. THE EC-BASED AIFS HAS
SHOWN THIS SOLUTION IN MOST RUNS, WITH THE GFS SUITE ALSO SHOWING
IT SOMETIMES, BUT ECMWF/CMC HAVE NOT FAVORED IT UNTIL TODAY. WITH
BETTER MODEL CONSENSUS NOW, THE WPC FORECAST TRENDED TOWARD THIS
TYPE OF SOLUTION USING A MULTI-MODEL DETERMINISTIC BLEND EARLY IN
THE PERIOD, AND GRADUALLY INCREASING THE PROPORTION OF ENSEMBLE
MEANS AS THE PERIOD PROGRESSED TO JUST OVER HALF BY DAY 7. THIS
LEADS TO LESS QPF ACROSS THE NORTHEAST COMPARED TO CONTINUITY, BUT
THE POTENTIAL FOR MORE ONSHORE IN THE CAROLINAS/MID-ATLANTIC,
PENDING UNCERTAINTIES IN POSITION OF COASTAL LOWS/FRONTS.
..WEATHER/HAZARDS HIGHLIGHTS
RAIN AND THUNDERSTORMS SHOULD FOCUS OVER THE NORTHERN AND CENTRAL
PLAINS ON SUNDAY AHEAD OF THE FIRST WESTERN TROUGH WHERE THERE IS
AMPLE LIFT, ALONG WITH SOME INSTABILITY NEAR A FRONTAL SYSTEM. THIS
WILL YIELD A MARGINAL RISK IN THE EXCESSIVE RAINFALL OUTLOOK (ERO)
FOR DAY 4/SUNDAY FOR POSSIBLE FLOODING CONCERNS. LIGHTER RAIN MAY
MAKE IT INTO THE UPPER MIDWEST BY MONDAY. MEANWHILE THE NEXT ROUND
OF TROUGHING WILL PUSH INTO THE WEST AND SPREAD ANOTHER ROUND OF
PRECIPITATION FIRST TO THE NORTHWEST SUNDAY, AND SPREADING EAST TO
THE NORTHERN ROCKIES MONDAY-TUESDAY AND INTO THE PLAINS TUESDAY-
WEDNESDAY. ADDITIONALLY, SOME MONSOONAL MOISTURE MAY REACH THE
SOUTHWEST, PRIMARILY NEW MEXICO.
INTO EARLY NEXT WEEK, MOISTURE NEAR A FRONTAL SYSTEM OVER THE
WESTERN ATLANTIC TO JUST SOUTH OF FLORIDA COULD PRODUCE ENHANCED
RAIN NEAR OR JUST OFFSHORE THE CAROLINAS AND VICINITY. SHOWERS WILL
ALSO BE PREVALENT ACROSS FLORIDA, THOUGH WITH LOWERING MOISTURE
LEVELS (PWS) COMPARED TO THE SHORT RANGE PERIOD, POTENTIALLY
LEADING TO LESSER AMOUNTS OVERALL THERE UNTIL THE FRONT LIFTS BACK
NORTH LATER NEXT WEEK. THE PATTERN IS UNCERTAIN ALOFT, BUT THE
TREND TOWARD AN UPPER LOW OVER THE SOUTHEAST/MID-ATLANTIC COULD
ALLOW FOR MORE RAIN TO SPREAD ONSHORE THERE, WHILE ANOTHER FRONT
DIVES IN WITH POSSIBLE COASTAL LOW DEVELOPMENT TO ENHANCE THE
POTENTIAL AS WELL. MONITOR UPDATES AS THIS FORECAST IS EVOLVING AND
WOULD AFFECT QPF AND CLOUDINESS.
SLIGHTLY COOLER THAN NORMAL TEMPERATURES ESPECIALLY FOR HIGHS ARE
LIKELY ACROSS THE WESTERN U.S. EARLY NEXT WEEK UNDERNEATH UPPER
TROUGHING. BUT THE UPPER RIDGE TO THE EAST WILL PROMOTE WARM
TEMPERATURES ACROSS THE CENTRAL U.S., WITH GREATEST ANOMALIES OF
10-20 DEGREES ABOVE AVERAGE IN THE MISSISSIPPI VALLEY WITH LESSER
ANOMALIES INTO THE PLAINS AND EAST INTO THE GREAT LAKES, OHIO
VALLEY, AND SOUTHEAST. TEMPERATURES WELL IN THE 90S WILL BE COMMON
THROUGH THE SOUTH NORTH INTO THE MIDWEST, AND A HANDFUL OF RECORD
HIGHS ARE POSSIBLE BUT CURRENTLY DO NOT LOOK TO BE WIDESPREAD.
RECENT MODEL TRENDS HAVE BEEN FOR SOME WARMER THAN AVERAGE
TEMPERATURES TO MOVE INTO THE NORTHEAST AS THE WEEK PROGRESSES.
TATE/SCHICHTEL
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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