540
FXUS02 KWBC 050654
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
254 AM EDT SUN JUL 5 2026
VALID 12Z WED JUL 08 2026 - 12Z SUN JUL 12 2026
...MAJOR TO EXTREME HEATWAVE TO SETTLE ACROSS THE SOUTHERN TIER
THIS WEEK...
..PATTERN OVERVIEW
BROAD UPPER-LEVEL RIDGING IS FORECAST TO BUILD OVER THE SOUTHERN
U.S. THIS WEEK WHILE TRANSIENT SHORTWAVES PROPAGATE THROUGH THE
GREAT LAKES AND NORTHEAST/MID-ATLANTIC. THE SOUTHERN RIDGE WILL
SUPPORT A MAJOR HEATWAVE INITIALLY OVER THE SOUTH/SOUTHEAST THEN
BUILDING INTO THE SOUTHWEST/GREAT BASIN. TROUGHING ALONG THE
U.S.-CANADIAN BORDER WILL PROMOTE DIURNAL SHOWERS AND THUNDERSTORMS
FROM THE NORTHERN PLAINS TO THE NORTHEAST, WITH A FOCUSED RISK FOR
HEAVIER RAIN OVER THE UPPER MIDWEST INTO THE GREAT LAKES TUE-WED.
TROUGHING OVER THE NORTHEAST PACIFIC WILL MAINTAIN NEAR TO BELOW
AVERAGE TEMPERATURES IN THE PACIFIC NORTHWEST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS ARE IN REASONABLY GOOD AGREEMENT ON THE SYNOPTIC PATTERN
BEGINNING THIS WEDNESDAY AND CONTINUING THROUGH THE WEEKEND. THUS,
A GENERAL MODEL BLEND CONSISTING OF THE AVAILABLE DETERMINISTIC AND
AI GUIDANCE WERE USED THROUGH DAY 5, BEFORE GRADUALLY INCORPORATING
THE ENSEMBLE MEANS THROUGH THE END OF THE PERIOD. THE UKMET WAS NOT
INCLUDED IN THE BLEND DUE TO AN OVERAMPLIFIED TROUGH OVER THE
MIDWEST COMPARED TO CONSENSUS.
..WEATHER/HAZARDS HIGHLIGHTS
A MAJOR HEAT WAVE IS EXPECTED TO EXPAND BENEATH A GROWING UPPER-
LEVEL RIDGE IN THE CENTRAL/SOUTHERN U.S.. THIS HEAT WAVE WILL
SPREAD FROM THE SOUTHEAST TO THE SOUTHERN PLAINS AND INTO THE
CENTRAL ROCKIES BY THE WEEKEND. HEAT INDICES BETWEEN 105-115 ARE
EXPECTED ACROSS THE SOUTH. TROUGHING IN THE NORTHEAST/MID-ATLANTIC
WILL SUPPORT CONTINUED HOT/MOIST SOUTHERLY FLOW INTO THE FLORIDA
PENINSULA, IN PARTICULAR, WHERE THERE'S A GROWING CONCERN FOR
EXTREME HEAT RISK BEGINNING ON WEDNESDAY AND CONTINUING INTO THE
WEEKEND. NO OVERNIGHT RELIEF FROM HOT TEMPERATURES WILL AFFECT
ANYONE WITHOUT ADEQUATE COOLING/HYDRATION AS WELL AS HEALTH
SYSTEMS, INDUSTRIES AND INFRASTRUCTURE.
SURFACE WAVES AND ATTENDANT FRONTS DRAPED ACROSS THE NORTHERN
PLAINS AND UPPER MIDWEST/GREAT LAKES WILL BE THE FOCUS FOR
SCATTERED THUNDERSTORMS ON WEDNESDAY. WELL ABOVE NORMAL MOISTURE
(>90TH PERCENTILE) AND INSTABILITY ALONG THE FRONT COULD COMBINE TO
PRODUCE HEAVY RAINFALL/FLASH FLOODING, BUT WEAK SHEARING WILL
LIKELY MITIGATE A SEVERE WEATHER THREAT. RAIN SHOWERS AND
THUNDERSTORMS WILL SHIFT INTO THE EAST COAST LATER IN THE WEEK AND
INTO NEXT WEEKEND. LASTLY, MONSOONAL MOISTURE MAY START TO INCREASE
OVER AT LEAST ARIZONA LATE NEXT WEEK INTO THE WEEKEND AS THE UPPER
HIGH DRIFTS A BIT FARTHER NORTH INTO UTAH.
KEBEDE
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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