556
FXUS02 KWBC 120800
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
400 AM EDT FRI SEP 12 2025
VALID 12Z MON SEP 15 2025 - 12Z FRI SEP 19 2025
..OVERVIEW
THE FORECAST PERIOD SHOULD BEGIN WITH AN UPPER TROUGH IN THE
PROCESS OF LIFTING OUT OF THE PLAINS WHILE ANOTHER TROUGH QUICKLY
FOLLOWS IN THE WEST TO SPREAD ENHANCED RAIN CHANCES FROM THE
NORTHWEST/WEST TO THE ROCKIES/PLAINS. TROUGHING IN THE EAST EARLY
NEXT WEEK, WITH UNCERTAINTY ON WHETHER A CLOSED UPPER LOW WILL
FORM NEAR THE COAST, WOULD BRING INCREASING 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 SHOW GOOD AGREEMENT ON LIFTING THE UPPER
TROUGH OUT OF THE PLAINS AS THE MEDIUM-RANGE PERIOD BEGINS ON
MONDAY WHILE THE NEXT UPPER TROUGH/CLOSED LOW TRAVERSES THE
NORTHWEST AND REACHES THE NORTH-CENTRAL PLAINS BY MIDWEEK. FOR THE
LATTER TROUGH, THE CMC AND ITS ENSEMBLE MEAN REMAIN ON THE FASTER
SIDE WITH THE EASTWARD PROGRESSION ACROSS THE NORTHERN PLAINS AS A
REX BLOCK PATTERN SETS UP OVER THE NORTH AMERICAN CONTINENT.
MODEL GUIDANCE ALSO IS AGREEABLE REGARDING AN UPPER RIDGE CENTERED
OVER THE EAST-CENTRAL U.S. BECOMING POSITIVELY TILTED AND MORE
AMPLIFIED. A RIDGE HAVING SUCH AMPLITUDE WILL TYPICALLY LEAD TO
DOWNSTREAM UPPER LOW FORMATION BUT WITH A LOW PREDICTABILITY
REGARDING EXACTLY WHERE AND WHEN THE UPPER LOW WILL FORM. THE EC-
AIFS HAS BEEN MOST PROMINENT IN DEVELOPING THIS UPPER LOW AS WELL
AS INTERACTING IT WITH A COASTAL FRONT/TROUGH, LEADING TO THE
DEVELOPMENT OF A COASTAL CYCLONE AT THE SURFACE. WHILE THIS IS A
PLAUSIBLE SCENARIO, THE WPC BLEND FOR LATE IN THE FORECAST PERIOD
CONTINUES TO BE BASED MAINLY ON THE CONSENSUS OF THE ENSEMBLE
MEANS, WHICH DEPICTS A COASTAL FRONT/TROUGH EXTENDING FROM MID-
ATLANTIC TO JUST OFF THE COAST OF THE SOUTHEASTERN U.S. FOR EARLIER
IN THE FORECAST PERIOD, A MULTI-MODEL BLEND OF BOTH THE LATEST
OPERATIONAL ECMWF, GFS, CMC AND THEIR ENSEMBLE MEANS SHOULD YIELD A
GOOD STARTING POINT. NOTE THAT THE QPF NEAR THE MID-ATLANTIC COAST
HAS CONTINUED TO TREND UPWARD AS THE ASSOCIATED COASTAL
FRONT/TROUGH GETS BETTER-DEFINED.
..WEATHER/HAZARDS HIGHLIGHTS
RAIN AND THUNDERSTORMS ASSOCIATED WITH A LOW PRESSURE SYSTEM WILL
BE IN THE PROCESS OF LIFTING OUT OF THE NORTHERN PLAINS INTO
SOUTHERN CANADA. MEANWHILE, THE NEXT UPPER TROUGH WILL SPREAD
ANOTHER ROUND OF PRECIPITATION EASTWARD ACROSS THE NORTHERN
ROCKIES MONDAY-TUESDAY AND INTO THE PLAINS TUESDAY-WEDNESDAY.
ADDITIONALLY, SOME MONSOONAL MOISTURE IS FORECAST TO REACH THE
SOUTHWEST, PRIMARILY NEW MEXICO.
INTO EARLY NEXT WEEK, MOISTURE CONVERGING NEAR A COASTAL FRONT/
TROUGH NORTH OF A WAVY FRONTAL SYSTEM FARTHER OFFSHORE COULD
PRODUCE ENHANCED RAIN NEAR OR JUST OFFSHORE THE CAROLINAS AND
VICINITY. A COASTAL LOW MAY DEVELOP TOWARD MIDWEEK NEAR THE
CAROLINA COAST, IN WHICH CASE, WINDY AND RAINY CONDITIONS WOULD
IMPACT THE COASTAL SECTIONS. MEANWHILE, THE TRAILING PORTION OF
THE STATIONARY FRONT WILL BE CLOSE ENOUGH TO BRING SOME SHOWERS
AND EMBEDDED THUNDERSTORMS INTO THE SOUTHERN FLORIDA PENINSULA
EARLY NEXT WEEK. HOWEVER, AS THE UPPER LOW NEAR THE EAST COAST
BEGINS TO LIFT NORTHWARD LATE NEXT WEEK, TROPICAL MOISTURE FROM
THE CARIBBEAN SEA APPEARS TO LIFT NORTHWARD AND BRING MORE
WIDESPREAD SHOWERS AND THUNDERSTORMS INTO SOUTH FLORIDA UNDER THE
INFLUENCE OF A SUBTROPICAL JET STREAM.
SLIGHTLY COOLER THAN NORMAL TEMPERATURES ESPECIALLY FOR HIGHS ARE
LIKELY ACROSS THE WESTERN U.S. EARLY NEXT WEEK UNDERNEATH UPPER
TROUGHING. IN CONTRAST, 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 CONTINUE TO FAVOR SOME WARMER THAN
AVERAGE TEMPERATURES TO MOVE INTO THE NORTHEAST AS THE WEEK
PROGRESSES.
KONG/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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page