043
FXUS02 KWNH 220658
PREEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
257 AM EDT TUE JUL 22 2025
VALID 12Z FRI JUL 25 2025 - 12Z TUE JUL 29 2025
***MAJOR HEAT WAVE CONTINUES FROM THE SOUTHEAST INTO PARTS OF THE
CENTRAL U.S. LATE THIS WEEK AND INTO THE WEEKEND***
..OVERVIEW
A LARGE UPPER RIDGE WILL BE IN PLACE ACROSS THE SOUTHEAST U.S.
THROUGH FRIDAY, AND THIS WILL BE THE MAIN DRIVER IN THE HEAT WAVE
THAT WILL BE ONGOING ACROSS MUCH OF THE NATION EAST OF THE ROCKIES.
BY THIS WEEKEND, THE UPPER RIDGE THEN BUILDS OVER THE CENTRAL
PLAINS WITH A WEAK TROUGH OVER THE NORTHEAST STATES. AN ACTIVE FLOW
PATTERN ALOFT WILL CONTINUE ACROSS THE NORTHERN TIER STATES AND
SOUTHERN CANADA, WITH A COUPLE OF COLD FRONTAL PASSAGES EXPECTED.
OUT WEST, AN UPPER TROUGH WITH POTENTIAL CLOSED LOW IS LIKELY NEAR
NORTHERN CALIFORNIA LATE IN THE WEEK, AND A WEAK SURFACE LOW ALONG
A DYING STATIONARY FRONT IS LIKELY NEAR THE GULF COAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
GOOD MODEL AGREEMENT EXISTS AMONG THE 00Z GUIDANCE SUITE REGARDING
THE MAIN UPPER LEVEL AND SURFACE PRESSURE PATTERN ACROSS THE
NATION FOR FRIDAY, AND THIS GENERALLY REMAINS THE CASE GOING INTO
THE WEEKEND AS WELL. LOOKING AHEAD TO EARLY NEXT WEEK, THE
EXPANSIVE UPPER RIDGE/HIGH IS THE MOST CONFIDENT ASPECT OF THE
FORECAST WITH THE BEST MODEL AGREEMENT. MORE MODEL DIFFERENCES
EXIST ACROSS THE NORTHEAST AND GREAT LAKES REGION WITH SHORTWAVE
ENERGY MOVING IN NORTHWEST FLOW ALOFT AROUND THE RIDGE AXIS. A
GENERAL MODEL BLEND WORKED FOR FRIDAY INTO THE WEEKEND, WITH A
TRANSITION TO ABOUT 40% ENSEMBLE MEANS BY NEXT TUESDAY.
..WEATHER/HAZARDS HIGHLIGHTS
A COLD FRONT IS PROGGED TO SLOWLY TRACK TOWARDS THE SOUTHEAST
ACROSS THE GREAT LAKES AND NEW ENGLAND FOR THE END OF THE WEEK,
WITH A WEAK WAVE OF LOW PRESSURE CROSSING SOUTHERN ONTARIO. THIS
BOUNDARY WILL BE INTERSECTING A HOT AND HUMID AIRMASS, AND THIS IS
EXPECTED TO FUEL THE DEVELOPMENT OF MULTIPLE THUNDERSTORM
COMPLEXES FROM IOWA AND MISSOURI EASTWARD TO THE NORTHERN OHIO
VALLEY AND MUCH OF THE NORTHEAST U.S. ON FRIDAY. A MARGINAL RISK
AREA IS VALID FOR DAY 4/FRIDAY FOR THESE REGIONS SINCE SOME OF THE
STORMS MAY HAVE CONVECTIVE TRAINING, AND THUS INCREASING THE RISK
OF LOCALIZED FLOODING WHERE THIS HAPPENS. THE MODEL SIGNAL FOR
HEAVIEST QPF IS MOST CONCENTRATED OVER CENTRAL PORTIONS OF ILLINOIS
AND INDIANA, AND THERE IS A GOOD CHANCE PARTS OF THOSE STATES MAY
EVENTUALLY NEED A SLIGHT RISK AS THE EVENT GETS CLOSER IN TIME. BY
DAY 5/SATURDAY, THE AXIS OF HEAVIER RAINFALL IS A LITTLE TO THE
SOUTH ACROSS THE CENTRAL OHIO VALLEY AND NORTHERN PORTIONS OF THE
MID-ATLANTIC, AND THIS IS WHERE THE DAY 5 MARGINAL RISK WILL BE.
ANOTHER AREA OF UNSETTLED WEATHER IS EXPECTED TO RESIDE ACROSS THE
FLORIDA PANHANDLE AND EXTENDING WESTWARD TO SOUTHEAST TEXAS ON
FRIDAY AS WELL. A WEAK SURFACE LOW IS LIKELY TO FORM ALONG A
LINGERING STATIONARY FRONT, AND THIS SHOULD GRADUALLY TRACK WEST
THROUGH FRIDAY BEFORE DISSIPATING ON SATURDAY. THE POTENTIAL
EXISTS FOR AN INCH OR TWO OF RAINFALL IN LOCALIZED CASES FROM
SOUTHERN LOUISIANA TO THE FLORIDA PANHANDLE, AND A MARGINAL RISK
AREA IS VALID FOR FRIDAY TO ACCOUNT FOR THIS. ACROSS THE DAKOTAS
AND INTO WESTERN MINNESOTA, THE NEXT FRONTAL BOUNDARY APPROACHING
FROM CENTRAL CANADA WILL LIKELY HAVE ENOUGH MOISTURE WITH IT TO
FUEL THE DEVELOPMENT OF MORE SHOWERS AND THUNDERSTORMS, SOME OF
WHICH MAY DEVELOP INTO COMPLEXES WITH MULTIPLE ROUNDS OF RAINFALL.
THEREFORE, A MARGINAL RISK AREA WILL BE VALID HERE FOR FRIDAY AND
LINGERING INTO SATURDAY.
THE OTHER BIG STORY WILL BE THE CONTINUING HEAT AND HUMIDITY ACROSS
A LARGE PORTION OF THE EAST-CENTRAL U.S. FOR THE END OF THE WEEK
AND INTO NEXT WEEKEND, COURTESY OF A LARGE UPPER HIGH INITIALLY IN
PLACE OVER THE MID-SOUTH AND SOUTHEAST. HEAT RISK IN THE MAJOR
CATEGORY WILL BE PREVALENT FROM THE DEEP SOUTH TO THE MIDWEST AND
EXTENDING EASTWARD TO INCLUDE TENNESSEE AND OHIO RIVER VALLEYS TO
CLOSE OUT THE WORK WEEK. SOME OF THIS HEAT WILL LIKELY REACH THE
EAST COAST BY FRIDAY AND SATURDAY WITH HIGHS WELL INTO THE 90S AND
HEAT INDICES OVER 100 DEGREES. HIGHS IN THE 100-105 DEGREE RANGE
ARE LIKELY FROM NORTHERN TEXAS TO KANSAS AS THE UPPER RIDGE BECOMES
RE-ESTABLISHED OVER THIS REGION BY SUNDAY AND EARLY NEXT WEEK. IT
WILL ALSO BE UNCOMFORTABLY WARM AND HUMID AT NIGHT, PROVIDING ONLY
LIMITED RELIEF FROM THE HEAT.
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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