218
FXUS02 KWBC 210656
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 AM EDT MON JUL 21 2025
VALID 12Z THU JUL 24 2025 - 12Z MON JUL 28 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 ANCHORED IN PLACE ACROSS THE SOUTH-
CENTRAL U.S. THROUGH THE END OF THE WEEK, 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 NEXT WEEKEND, THE UPPER RIDGE
THEN BECOMES RE-ESTABLISHED 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 SURFACE LOW ALONG A WEAKENING
STATIONARY FRONT IS LIKELY NEAR THE GULF COAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 00Z MODEL GUIDANCE SUITE AND AIFS MODEL FEATURES VERY GOOD
OVERALL SYNOPTIC SCALE AGREEMENT FOR THE END OF THE WEEK, WITH A
GENERAL DETERMINISTIC MODEL BLEND WORKING WELL AS A STARTING POINT
IN THE FORECAST PROCESS. ALL OF THE GUIDANCE CONTINUES TO REMAIN
WEAK WITH ANY SURFACE LOW DEVELOPMENT OVER THE NORTHERN GULF, BUT
WITH ENOUGH MOISTURE CONVERGENCE AND LIFT FOR HEAVY RAINFALL FROM
SOUTHEAST TEXAS TO THE FLORIDA PENINSULA. GOING INTO THE WEEKEND,
THE GREATEST MODEL DIFFERENCES RESIDE ACROSS SOUTHERN CANADA WITH
THE TIMING AND POSITION OF A LOW PRESSURE SYSTEM AND TRAILING COLD
FRONT THAT WILL AFFECT AREAS FROM MONTANA TO MINNESOTA. THE
ENSEMBLE MEANS WERE GRADUALLY INCREASED TO ABOUT 50% BY MONDAY AMID
GROWING MESOSCALE DIFFERENCES.
..WEATHER/HAZARDS HIGHLIGHTS
A COLD FRONT IS PROGGED TO SLOWLY DROP SOUTHWARD ACROSS THE UPPER
MIDWEST AND GREAT LAKES REGION FOR THE END OF THE WEEK, WITH A
WEAK WAVE OF LOW PRESSURE CROSSING LAKE SUPERIOR. THIS BOUNDARY
WILL BE INTERSECTING A WARM AND VERY HUMID AIRMASS, AND THIS IS
EXPECTED TO FUEL THE DEVELOPMENT OF MULTIPLE THUNDERSTORM COMPLEXES
FROM IOWA TO MICHIGAN ON THURSDAY, AND THEN ACROSS THE NORTHERN
OHIO VALLEY AND EXTENDING TO NORTHERN NEW ENGLAND ON FRIDAY. A
MARGINAL RISK AREA IS VALID FOR BOTH DAY 4 AND DAY 5 FOR THESE
REGIONS SINCE SOME OF THE STORMS MAY HAVE CONVECTIVE TRAINING, AND
THUS INCREASING THE RISK OF LOCALIZED FLOODING WHERE THIS HAPPENS.
ANOTHER AREA OF UNSETTLED WEATHER IS EXPECTED TO RESIDE ACROSS THE
FLORIDA PANHANDLE AND EXTENDING WESTWARD TO SOUTHEAST TEXAS TO
CLOSE OUT THE WORK WEEK. A SURFACE LOW IS LIKELY TO FORM ALONG A
LINGERING STATIONARY FRONT, AND THIS SHOULD GRADUALLY TRACK WEST
THROUGH FRIDAY. THE POTENTIAL EXISTS FOR SEVERAL INCHES OF
RAINFALL IN LOCALIZED CASES FROM SOUTHERN LOUISIANA TO THE FLORIDA
PANHANDLE, AND MARGINAL RISK AREAS ARE VALID FOR THURSDAY AND
FRIDAY TO ACCOUNT FOR THIS, WITH SOME POTENTIAL FOR AN EVENTUAL
SLIGHT RISK IN LATER FORECASTS AS THE MODEL GUIDANCE COMES INTO
BETTER FOCUS.
ELSEWHERE ACROSS THE NATION, MOISTURE ASSOCIATED WITH THE SOUTHWEST
U.S. MONSOON WILL LIKELY IMPROVE COMPARED TO RECENT DAYS, WITH
SOME LINGERING SHOWERS/STORMS ACROSS NORTHEAST NEW MEXICO AND INTO
EASTERN COLORADO. HOWEVER, THERE MAY BE A FEW CONVECTIVE CELLS
THAT ARE SLOW MOVING ACROSS BURN SCAR AND OTHER SENSITIVE AREAS,
AND THEREFORE A MARGINAL RISK REMAIN PRUDENT IN THE EXCESSIVE
RAINFALL OUTLOOK FOR THURSDAY, BUT CURRENTLY NOT NEEDED FOR FRIDAY.
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.
THE OTHER BIG STORY WILL BE THE BUILDING HEAT ACROSS A LARGE
PORTION OF THE EAST-CENTRAL U.S. FOR THE SECOND HALF OF THE WEEK
AND INTO NEXT WEEKEND, COURTESY OF A LARGE UPPER HIGH BECOMING
ANCHORED OVER THE MID-SOUTH. 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 NEXT WEEKEND FOLLOWING THE PLEASANT STRETCH OF
COOLER WEATHER FOR THE FIRST HALF OF THE WEEK. HIGHS WELL INTO THE
90S AND EVEN SOME LOW 100S WILL BE COMMONPLACE FROM THE CENTRAL
PLAINS TO THE EAST COAST, WITH THE HOTTEST READINGS ACROSS
OKLAHOMA, TEXAS, AND ARKANSAS. 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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