610
FXUS02 KWBC 231724
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
124 PM EDT WED JUL 23 2025
VALID 12Z SAT JUL 26 2025 - 12Z WED JUL 30 2025
...MAJOR AND PERSISTENT HEAT WAVE CONTINUES FROM THE SOUTHEAST TO
THE CENTRAL U.S. THIS WEEKEND INTO NEXT WEEK...
..GENERAL OVERVIEW
AN UPPER LEVEL RIDGE WILL DOMINATE THIS FORECAST PERIOD FROM THE
WESTERN HIGH PLAINS TO THE SOUTHEAST STATES. THE UPPER HIGH IS
INITIALLY CENTERED NEAR THE SOUTHEAST COAST ON SATURDAY, BUT BUILDS
BACK FARTHER TO THE WEST ACROSS THE PLAINS GOING INTO EARLY NEXT
WEEK AS THE OVERALL PATTERN STARTS TO BECOME MORE AMPLIFIED. THIS
CONTINUES TO SUPPORT AN EXPANSIVE AND DANGEROUS HEAT WAVE FOR THIS
REGION. AN UPPER TROUGH OVER CENTRAL CANADA WILL LIKELY AMPLIFY
FURTHER DOWNSTREAM OF THIS UPPER RIDGE ACROSS THE NORTHEAST BY THE
MIDDLE OF THE WEEK AND BEYOND, SIGNALING A RETURN TO COOLER
CONDITIONS BY THE END OF THE FORECAST PERIOD FOR AT LEAST THE
NORTHEAST. SHORTWAVE ENERGY TRACKING AROUND THE NORTHERN PERIPHERY
OF THE UPPER RIDGE WILL FUEL THE DEVELOPMENT OF MULTIPLE
THUNDERSTORM COMPLEXES FROM THE NORTHERN PLAINS TO THE GREAT LAKES
AND THE NORTHEAST STATES.
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATEST GUIDANCE CONTINUES TO SHOW ABOVE AVERAGE AGREEMENT THROUGH
THE ENTIRE PERIOD, ESPECIALLY WITH RESPECT TO THE EXPANDING UPPER
RIDGE ACROSS THE SOUTH-CENTRAL U.S. AND SOUTHEAST. THERE IS STILL
SOME DISAGREEMENT IN HOW AMPLIFIED TROUGHING GETS OVER THE GREAT
LAKES/NORTHEAST NEXT WEEK, AND SOME UNCERTAINTY IN THE DETAILS OF
INDIVIDUAL VORTS OF ENERGY MOVING ON TOP OF THE RIDGE. THESE
DETAILS DO AFFECT QPF DISTRIBUTION AND AMOUNTS THROUGH THE PERIOD,
MUCH OF WHICH CAN BE REFINED CLOSER IN TIME. THE WPC FORECAST TODAY
WAS ABLE TO UTILIZE A BLEND OF THE DETERMINISTIC GUIDANCE THE
FIRST HALF OF THE PERIOD, GRADUALLY SHIFTING TOWARDS A 60 PERCENT
DETERMINISTIC (GFS, ECMWF, AND CMC) AND 40 PERCENT ENSEMBLE MEANS
(GEFS AND ECENS). OVERALL, THIS MAINTAINS GOOD CONTINUITY WITH THE
OVERNIGHT WPC FORECAST AS WELL.
..WEATHER/HAZARDS HIGHLIGHTS
THE OVERALL WEATHER PATTERN IS EXPECTED TO REMAIN RATHER ACTIVE
ACROSS THE NORTHERN TIER STATES AS STORM SYSTEMS TRAVERSE THE
NORTHERN PERIPHERY OF THE UPPER HIGH. THE FIRST AREA OF CONCERN
WILL BE FROM THE NORTHERN OHIO VALLEY AND SOUTHERN MICHIGAN TO THE
NORTHEAST U.S. WITH A FRONTAL BOUNDARY SLOWLY DROPPING SOUTHWARD.
SCATTERED TO NUMEROUS SHOWERS AND STORMS ARE LIKELY ON SATURDAY
WITH THE POTENTIAL FOR SOME CONVECTIVE TRAINING, AND A MARGINAL
RISK REMAINS VALID ON THE DAY 4 EXCESSIVE RAINFALL OUTLOOK. THIS
REACHES THE NORTHEAST ON SUNDAY WITH ANOTHER MARGINAL RISK ON THE
ERO IN PLACE. THE OTHER AREA OF CONCERN WILL BE ACROSS THE UPPER
MIDWEST, WITH THE HEAVIEST RAINFALL LIKELY ON SUNDAY AS A SURFACE
LOW DEVELOPS ALONG A COLD FRONT AND INTERCEPTS AN ANOMALOUSLY HUMID
AIRMASS ACROSS MUCH OF MINNESOTA. GIVEN GOOD MODEL QPF AGREEMENT
FOR THIS TIME RANGE AND THE RECENT HEAVY RAINFALL, A SLIGHT RISK
AREA IS HIGHLIGHTED FROM EXTREME EASTERN NORTH DAKOTA, ACROSS
NORTHERN MINNESOTA, AND INTO NORTHWEST WISCONSIN FOR THE DAY
5/SUNDAY ERO.
ELSEWHERE ACROSS THE NATION, THE POSITION OF THE UPPER HIGH/RIDGE
OVER THE WESTERN HIGH PLAINS BY EARLY NEXT WEEK WILL RESULT IN
DEEPER MONSOONAL MOISTURE BEING ADVECTED NORTHWARD ACROSS THE
DESERT SOUTHWEST. THIS FIRST BECOMES NOTICEABLE ACROSS SOUTHERN NEW
MEXICO ON SUNDAY, BUT BECOMES MORE WIDESPREAD AND ENCOMPASSES MORE
OF NEW MEXICO AND INTO MUCH OF CENTRAL/EASTERN ARIZONA AND
COLORADO BY MONDAY AND TUESDAY. THEREFORE, THE DAY 5/SUNDAY ERO
FEATURES A MARGINAL RISK AREA CENTERED OVER SOUTHWESTERN NEW
MEXICO. HEAVY SHOWERS AND STORMS FROM SEA BREEZE CONVERGENCE OVER
FLORIDA IS LIKELY DURING THE AFTERNOON HOURS EARLY NEXT WEEK, AND
SCATTERED STORMS WILL ALSO BE POSSIBLE ACROSS PORTIONS OF THE
NORTHERN ROCKIES AND THE CASCADES.
OTHERWISE, HEAT WILL CONTINUE TO MAKE WEATHER HEADLINES ACROSS A
LARGE EXPANSE OF THE CENTRAL AND EASTERN U.S. GIVEN THE SIZE OF THE
UPPER RIDGE AND THE JET STREAM WELL TO THE NORTH. HEAT INDICES OF
100 TO 110 DEGREES ARE LIKELY FROM THE DELMARVA PENINSULA TO
FLORIDA THIS WEEKEND, AND ALSO ACROSS MUCH OF THE CENTRAL AND
SOUTHERN PLAINS. THERE WILL LIKELY BE SOME ABATEMENT IN THE HEAT
FOR THE MID- ATLANTIC AND NORTHEAST FOR EARLY TO MID NEXT WEEK AS
AN UPPER TROUGH BEGINS TO AMPLIFY ACROSS EASTERN CANADA AND INTO
NEW ENGLAND. HOWEVER, THE HEAT LIKELY BECOMES EVEN WORSE FOR THE
MIDWEST TO THE DEEP SOUTH WITH HEAT INDICES OF 105 TO 115 DEGREES
FOR MANY AREAS, EQUATING TO WIDESPREAD MAJOR TO EXTREME HEATRISK.
PLEASE SEE KEY MESSAGES BEING ISSUED FROM WPC FOR THIS SIGNIFICANT
AND POTENTIALLY DANGEROUS HEAT WAVE.
SANTORELLI/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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