512
FXUS02 KWBC 010659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT WED JUL 1 2026
VALID 12Z SAT JUL 04 2026 - 12Z WED JUL 08 2026
...SIGNIFICANT HEAT WAVE EXPECTED TO LAST INTO AT LEAST SATURDAY
FOR THE MIDWEST TO EASTERN U.S. BEFORE WANING EARLY NEXT WEEK..
..PATTERN OVERVIEW
THE STRONG RIDGE SUPPORTING A SIGNIFICANT AND DANGEROUS HEAT WAVE
DURING THE SHORT RANGE PERIOD SHOULD FINALLY BEGIN TO WEAKEN
SOMEWHAT BY THE MEDIUM RANGE PERIOD, HOWEVER HAZARDOUS HEAT MAY
STILL CONTINUE THROUGH THE WEEKEND, ESPECIALLY FOR PARTS OF THE
EAST. ENERGY FROM THE WEST SHOULD EVENTUALLY WORK ITS WAY INTO THE
NORTHERN PLAINS AND GREAT LAKES SUPPRESSING THE RIDGE COMPLETELY BY
EARLY NEXT WEEK. RIDGING THEN LOOKS TO BUILD BACK INTO THE FOUR
CORNERS REGION NEXT WEEK. SHOWERS AND STORMS WILL EXPAND ACROSS THE
OHIO VALLEY AND THE SOUTH/EAST NEXT WEEKEND AND EARLY NEXT WEEK AS
THE RIDGE WEAKENS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT WITH THE SYNOPTIC SCALE
PATTERN THROUGH THE PERIOD, BUT UNCERTAINTY REMAINS WITH THE
DETAILS/EVOLUTION OF ENERGY TRAVERSING THE FLOW IN THE WEST AND THE
TIMING OF RIDGE BREAK DOWN OVER THE EAST. MOST OF THE GUIDANCE
SHOW THE PEAK OF THE HEAT WAVE DURING THE SHORT RANGE, AND BY THE
MEDIUM RANGE PERIOD ENERGY FROM THE WEST SHOULD WORK INTO THE
MIDWEST/GREAT LAKES WEAKENING THE RIDGE AND OVERALL OPPRESSIVE
HEAT. HOW QUICKLY AND HOW MUCH THE RIDGE IS SUPPRESSED IS STILL IN
QUESTION, WHICH LEADS TO UNCERTAINTY IN MAXIMUM TEMPERATURES FOR
THIS WEEKEND. AMPLITUDE OF THIS FEATURE AS IT CROSSES INTO THE
NORTHEAST NEXT WEEK IS STILL SOMEWHAT UNCERTAIN, BUT THERE HAS
DEFINITELY BEEN A TREND TOWARDS A BIT FLATTER FLOW.
UPSTREAM, A RIDGE BUILDS OVER THE FOUR CORNERS REGION THROUGH THE
WEEKEND AND EARLY NEXT WEEK. MODELS SHOW AGREEMENT ON A DEEPER
SHORTWAVE OR UPPER LOW MOVING INTO THE NORTHWEST, WHICH MAY
EVENTUALLY DISPLACE THE RIDGE A BIT EASTWARD WITH TIME NEXT WEEK.
THE WPC FRONTS/PRESSURES PROGS WAS BASED ON A BLEND OF THE
DETERMINISTIC AND MACHINE-LEARNING GUIDANCE FOR THE FIRST HALF OF
THE PERIOD, INCREASING WEIGHTING OF THE ENSEMBLE MEANS TO JUST OVER
HALF BY THE LATTER HALF OF THE PERIOD. THIS GENERALLY MAINTAINED
GOOD AGREEMENT WITH THE PREVIOUS WPC FORECAST AND THE NBM, ALBEIT
WITH SENSIBLE WEATHER ADJUSTMENTS TO THE NBM FOCUSED PRIMARILY FOR
MAX T AND AFTERNOON DEWPOINTS UNDERNEATH THE RIDGE EARLY PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
A SIGNIFICANT AND MAJOR HEAT WAVE SET TO BEGIN BY THE MIDDLE OF
THIS WEEK MAY STILL CONTINUE INTO NEXT WEEKEND FOR PARTS OF THE
MIDWEST AND MUCH OF THE EAST. WIDESPREAD AND DAILY RECORD BREAKING
MAXIMUM TEMPERATURES INTO THE 90S TO LOW 100S, COMBINED WITH HIGH
HUMIDITY, WILL RESULT IN HEAT INDICES APPROACHING OR EXCEEDING
105-110 IN MANY PLACES, ESPECIALLY FOR SATURDAY. THIS EQUATES TO
WIDESPREAD MAJOR TO EXTREME HEATRISK FROM THE MIDWEST/MISSISSIPPI
VALLEY EASTWARD TO THE EAST COAST. OVERNIGHT LOWS WILL LINGER AND
ALSO BE QUITE WARM, WITH NUMEROUS RECORD HIGH MINIMUMS POSSIBLE,
BRINGING LITTLE TO NO RELIEF FROM THE HEAT IN THE NIGHTTIME HOURS.
HEAT MAY FINALLY BEGIN TO ABATE BY SUNDAY, WITH UPPER TEMPERATURE
LIMITS THROUGH THE WEEKEND POSSIBLY RESTRICTED BY INCREASING
CLOUDS/CONVECTION AS RIDGE BREAKDOWN BEGINS. ABOVE NORMAL
TEMPERATURES SHOULD EXPAND WESTWARD INTO THE SOUTHERN AND CENTRAL
PLAINS AS WELL, WITH TEMPERATURES OUT WEST NEAR TO BELOW NORMAL
UNDERNEATH OF GENERAL/WEAKENED TROUGHING.
RAIN AND THUNDERSTORMS SHOULD EXPAND IN COVERAGE ACROSS MUCH OF
THE EASTERN HALF OF THE NATION THIS WEEKEND WITHIN A VERY WARM,
MOIST, AND UNSTABLE AIR MASS. FAIRLY WEAK OVERALL FLOW MAY ALSO
HELP TO SUPPORT AT LEAST A LOCALIZED FLASH FLOOD THREAT ACROSS MUCH
OF THIS REGION, WITH POSSIBLY SOME BETTER CONVECTION FOCUS NEAR A
WAVY FRONTAL BOUNDARY FROM THE MIDWEST TO THE MID-ATLANTIC. WPC
MARGINAL RISKS ARE IN PLACE FROM THE NORTH-CENTRAL PLAINS INTO
PARTS OF THE EAST FOR THE DAYS 4/SATURDAY AND 5/SUNDAY EXCESSIVE
RAINFALL OUTLOOKS.
ELSEWHERE, DIURNALLY DRIVEN SHOWERS AND STORMS ARE EXPECTED FROM
PARTS OF THE CENTRAL GULF COAST TO FLORIDA MOST OF THE PERIOD WITH
INCREASING MOISTURE. SHOWERS MAY REFIRE AGAIN LATER IN THE PERIOD
FOR PARTS OF THE SOUTHERN/CENTRAL ROCKIES AND HIGH PLAINS, AS WELL
AS THE NORTHERN TIER AHEAD OF ADDITIONAL SHORTWAVE ENERGY. THE WEST
LOOKS TO REMAIN MOSTLY DRY THROUGH THE ENTIRE PERIOD.
SANTORELLI
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, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY MESSAGES
ARE AT:
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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