371
FXUS02 KWBC 291939
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
339 PM EDT MON JUN 29 2026
VALID 12Z THU JUL 02 2026 - 12Z MON JUL 06 2026
...SIGNIFICANT, DANGEROUS, AND RECORD BREAKING HEAT WAVE EXPECTED
NEXT WEEK FOR THE CENTRAL TO EASTERN U.S...
..PATTERN OVERVIEW
STRONG RIDGE ANCHORED OVER THE EASTERN HALF OF THE COUNTRY,
SUPPORTING A SIGNIFICANT AND DANGEROUS HEAT WAVE FOR MILLIONS OF
PEOPLE. ACROSS THE WEST AN AMPLIFIED TROUGH WILL BE WORKING TO
SUPPRESS THE EASTERN RIDGE SLIGHTLY BY NEXT WEEKEND AS A SHORTWAVE
SLIDES INTO THE GREAT LAKES. RIDGING MAY BUILD BACK ACROSS THE
SOUTH- CENTRAL PLAINS BY LATER IN THE PERIOD AS WELL. SHOWERS AND
THUNDERSTORMS WILL BE MOST LIKELY OVER THE UPPER MIDWEST/GREAT
LAKES, THE GULF COAST, AND EVENTUALLY ACROSS THE EAST NEXT WEEKEND
AND EARLY NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST GUIDANCE CONTINUES TO HAVE GOOD AGREEMENT WITH THE
SYNOPTIC SCALE PATTERN BUT UNCERTAINTY REMAINS WITH THE
DETAILS/EVOLUTION OF ENERGY TRAVERSING THE FLOW IN THE WEST AND THE
DEGREE OF PROGRESSIVENESS TO BREAKDOWN THE RIDGE OVER THE EAST.IN
REGARDS TO THE UPPER RIDGE, CONFIDENCE AND PREDICTABILITY REMAIN
HIGH THROUGH THE END OF THE WEEK. A SHORTWAVE WAVE NEAR THE PACIFIC
NORTHWEST IS PROGGED TO HEAD EAST AND WILL BEGIN TO BREAKDOWN THE
RIDGE AS THE EXTENDED PERIOD PROGRESSES. AS PREVIOUSLY NOTED, SOME
OF THE GUIDANCE SHOWS GRADUAL AMPLIFICATION OF THIS FEATURE AS WELL
WHICH SHOULD ALLOW FOR RIDGING TO BUILD BACK UPSTREAM OVER THE
SOUTH- CENTRAL AND SOUTHWEST U.S.. CONFIDENCE IS INCREASING THAT
THE RIDGE SHOULD WEAKEN BY THE END OF THE PERIOD, BUT THE TIMING OF
WHEN THIS BEGINS IS STILL QUITE UNCERTAIN. THE GUIDANCE IS MIXED
ON HOW STRONG THIS SHORTWAVE WILL BE AS IT MOVES INTO THE GREAT
LAKES/MIDWEST EARLY NEXT WEEK. THERE IS ALSO SOME TIMING
UNCERTAINTIES ON ANOTHER TROUGH ENTERING THE NORTHWEST LATE PERIOD
IN ADDITION.
THE WPC FRONTS/PRESSURES FORECAST FOR TONIGHT USED A BLEND OF THE
DETERMINISTIC GUIDANCE FOR THE FIRST HALF OF THE PERIOD, GRADUALLY
INCREASING WEIGHTING OF THE ENSEMBLE MEANS TO 50 PERCENT OF THE
BLEND BY THE LATTER HALF. GENERALLY MAINTAINED GOOD AGREEMENT WITH
THE PREVIOUS WPC FORECAST, WITH SENSIBLE WEATHER ADJUSTMENTS TO THE
NBM NEEDED PRIMARILY FOR MAX T AND AFTERNOON DEWPOINTS.
..WEATHER/HAZARDS HIGHLIGHTS
THE PROMINENT WEATHER HAZARD FOR THE EXTENDED PERIOD WILL BE THE
WIDESPREAD HEAT WAVE AFFECTING MUCH OF THE CENTRAL TO EASTERN U.S.
SPANNING THE SHORT TO MEDIUM RANGE PERIOD. IT IS EXPECTED TO REACH
ITS PEAK AROUND THURSDAY OR FRIDAY OF THIS WEEK BEFORE TEMPERATURES
TREND LOWER. 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. SOME OF THESE VALUES MAY BREAK ALL TIME RECORDS AS
WELL. THIS EQUATES TO WIDESPREAD MAJOR TO EXTREME HEATRISK FROM THE
MIDWEST/MISSISSIPPI VALLEY EASTWARD TO THE EAST COAST. OVERNIGHT
LOWS WILL 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 FROM WEST TO EAST
THIS WEEKEND, WITH UPPER TEMPERATURE LIMITS POSSIBLY RESTRICTED BY
CLOUDS/CONVECTION. ABOVE NORMAL TEMPERATURES SHOULD EXPAND WESTWARD
INTO THE SOUTHERN AND CENTRAL PLAINS AS WELL, WITH TEMPERATURES
OUT WEST NEAR TO BELOW NORMAL UNDERNEATH OF THE UPPER TROUGH.
RAIN AND THUNDERSTORMS ASSOCIATED WITH A SLOW MOVING FRONTAL
BOUNDARY WILL IMPACT PARTS OF THE NORTHERN PLAINS TO UPPER MIDWEST
AND GREAT LAKES INTO NEXT WEEKEND. MOISTURE ANOMALIES AND
INSTABILITY WITHIN FAIRLY WEAK FLOW MAY SUPPORT AT LEAST A
LOCALIZED FLASH FLOOD THREAT. WPC HIGHLIGHTS MUCH OF THIS REGION
WITHIN A MARGINAL RISK FOR BOTH THE DAY 4/THURSDAY AND DAY 5/FRIDAY
EXCESSIVE RAINFALL OUTLOOKS. SOME OF THIS ACTIVITY WILL LIKELY
MAKE ITS WAY INTO PARTS OF THE NORTHEAST AS WELL AS IT ROUNDS THE
NORTHERN PERIPHERY OF THE MID/UPPER LEVEL RIDGE.
ELSEWHERE, DIURNALLY DRIVEN SHOWERS AND STORMS ARE EXPECTED FROM
THE CENTRAL GULF COAST TO FLORIDA WITH MOISTURE INCREASING SOUTH OF
THE UPPER RIDGE. SHOWERS MAY INCREASE ACROSS PARTS OF THE OHIO
VALLEY AND EAST BY NEXT WEEKEND AS THE UPPER RIDGE SLIGHTLY WEAKENS
AND UPPER LEVEL ENERGY INTRUDES INTO THE REGION.
CAMPBELL/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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