851
FXUS02 KWBC 190653
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
253 AM EDT SAT JUL 19 2025
VALID 12Z TUE JUL 22 2025 - 12Z SAT JUL 26 2025
...MAJOR HEAT WAVE BUILDING FROM THE SOUTHEAST INTO PARTS OF THE
CENTRAL U.S. NEXT WEEK AND BEYOND...
..OVERVIEW
THE OVERALL WEATHER PATTERN NEXT WEEK WILL BE DOMINATED BY A
BUILDING UPPER LEVEL RIDGE THAT WILL BE SITUATED OVER THE DEEP
SOUTH AND EXTENDING NORTH TO THE TENNESSEE AND OHIO RIVER VALLEYS.
HEAT AND HUMIDITY BUILD TO DANGEROUS LEVELS ACROSS MUCH OF THE
CENTRAL U.S. AND EXTENDING TO THE SOUTHEAST AND DEEP SOUTH. AN
ACTIVE FLOW PATTERN WILL BE IN PLACE TO THE NORTH OF THIS HIGH AS
MULTIPLE SHORTWAVE IMPULSES TRACK EASTWARD OVER THE NORTHERN TIER
STATES AND THEN NEW ENGLAND. A COLD FRONT PROVIDES SOME RELIEF
FROM THE RECENT HEAT AND HUMIDITY FROM THE MID-ATLANTIC TO THE
NORTHEAST TO START THE WEEK, FOLLOWED BY HOTTER WEATHER MID-WEEK
AND BEYOND. MEANWHILE, AN UPPER LEVEL TROUGH LIKELY DEVELOPS NEAR
THE WEST COAST GOING INTO EARLY NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 12Z MODEL GUIDANCE SUITE HAS A GOOD DEPICTION OF THE GENERAL
WEATHER PATTERN TO START THE FORECAST PERIOD TUESDAY, AND THUS A
DETERMINISTIC MODEL BLEND WORKS VERY WELL AS A STARTING POINT. THE
PAST FEW RUNS OF THE GFS ARE MORE ROBUST WITH SHORTWAVE ENERGY
CROSSING NEAR THE U.S./CANADA BORDER AND LIMIT THE NORTHWARD EXTENT
OF THE MAIN UPPER RIDGE MORE SO THAN THE OVERALL MODEL CONSENSUS
AND THE AIFS GUIDANCE, SO ITS CONTRIBUTION TO THE PREFERRED BLEND
WAS A LITTLE LESS THAN THE CMC AND ECMWF MODELS. ELSEWHERE, THERE
REMAIN SOME PLACEMENT DIFFERENCES WITH THE UPPER TROUGH THAT
DEVELOPS OFF THE CALIFORNIA COAST LATE IN THE WEEK, BUT IT DOES NOT
CURRENTLY APPEAR TO HAVE A MAJOR EFFECT ON THE OVERALL FORECAST.
THE ENSEMBLE MEANS WERE GRADUALLY INCREASED TO ABOUT 50% BY
SATURDAY.
..WEATHER/HAZARDS HIGHLIGHTS
IT REMAINS THE CASE THAT AN AXIS OF UNSETTLED WEATHER WILL REMAIN
IN PLACE ACROSS THE UPPER MIDWEST AND ALSO THE SOUTHEAST U.S. FOR
THE BEGINNING TO MIDDLE OF THE WEEK. THUNDERSTORM COMPLEXES
TRAVELING AROUND THE NORTHERN PERIPHERY OF THE BIG UPPER HIGH WILL
LIKELY PRODUCE LOCALIZED AREAS OF HEAVY RAINFALL, POTENTIALLY
EXCEEDING AN INCH PER HOUR OR MORE. THEREFORE, A BROAD MARGINAL
RISK AREA EXTENDS FROM THE EASTERN DAKOTAS TO THE WESTERN GREAT
LAKES ON TUESDAY WHERE A COLD FRONT WILL BE INTERSECTING A WARM AND
HUMID AIRMASS TO THE SOUTH. THERE IS A GOOD CHANCE THAT A SLIGHT
RISK COULD EVENTUALLY BE NEEDED IN LATER OUTLOOKS AS CONFIDENCE ON
THE MAIN QPF AXIS BECOMES MORE CERTAIN. ACROSS THE DEEP SOUTH AND
NORTHERN FLORIDA, A LINGERING STATIONARY FRONT WILL HELP FOCUS DEEP
MOISTURE WITH A POTENTIAL WAVE OF LOW PRESSURE DEVELOPING ALONG IT,
WITH SOME 1-3 INCH RAINFALL TOTALS POSSIBLE FOR SOME AREAS.
THEREFORE, A MARGINAL RISK AREA IS VALID HERE FOR BOTH TUESDAY AND
WEDNESDAY.
HEAT WILL ONCE AGAIN MAKE WEATHER HEADLINES FOR MUCH OF NEXT WEEK
ACROSS A LARGE PORTION OF THE SOUTHERN AND CENTRAL U.S. WITH A
LARGE UPPER HIGH BECOMING ANCHORED OVER THE MID-SOUTH. WIDESPREAD
MAJOR IMPACTS ON THE HEAT RISK SCALE ARE EXPECTED FROM THE CENTRAL
PLAINS TO THE SOUTHEAST STATES EARLY IN THE WEEK, AND THESE HIGHER
IMPACTS THEN REACH THE MIDWEST AND OHIO VALLEY BY MID TO LATE WEEK.
THIS WILL BE DUE TO WIDESPREAD HIGHS IN THE LOWER 90S TO LOW 100S
FOR MANY OF THESE AREAS, IN COMBINATION WITH DEWPOINTS WELL INTO
THE 70S, AND OVERNIGHT LOWS REMAINING UNCOMFORTABLY WARM. THIS WILL
LIKELY HAVE SOME STAYING POWER BEYOND THIS FORECAST PERIOD BASED
ON THE LATEST WEEK TWO OUTLOOK FROM THE CLIMATE PREDICTION CENTER
FROM THE CENTRAL PLAINS TO THE GULF COAST REGION.
ELSEWHERE ACROSS THE NATION, THERE SHOULD BE JUST ENOUGH MONSOONAL
MOISTURE IN PLACE ACROSS EASTERN ARIZONA AND MUCH OF NEW MEXICO,
AND PROBABLY EXTENDING INTO SOUTHERN PORTIONS OF COLORADO, AND
GIVEN THE POTENTIAL FOR SOME ISOLATED SLOW MOVING STORMS, A
MARGINAL RISK IS IN PLACE FOR BOTH TUESDAY AND WEDNESDAY. ACROSS
THE EAST COAST REGION, A COLD FRONT IS FORECAST TO CLEAR THE
NORTHEAST AND THE MID-ATLANTIC REGION THROUGH TUESDAY, AND
BRINGING A HIGHER QUALITY AIRMASS AFTER ALL OF THE HEAT AND
OPPRESSIVE HUMIDITY LATELY AND LOWER RAIN CHANCES. HOWEVER, THE
HEAT WILL LIKELY RETURN TOWARDS THE END OF THE WEEK AS THE CANADIAN
SURFACE HIGH MOVES OFFSHORE AND A MORE SOUTHERLY FLOW COMMENCES.
HAMRICK
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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