114
FXUS02 KWBC 271953
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
353 PM EDT SAT JUN 27 2026
VALID 12Z TUE JUN 30 2026 - 12Z SAT JUL 04 2026
...SIGNIFICANT, DANGEROUS HEAT WAVE EXPECTED NEXT WEEK FOR THE
CENTRAL TO EASTERN U.S...
..PATTERN OVERVIEW
A STRONG RIDGE WILL BE ANCHORED OVER THE EASTERN HALF OF THE
COUNTRY, SUPPORTING A SPRAWLING DANGEROUS HEAT WAVE AND HIGH
HUMIDITY. MEANWHILE AN AMPLIFIED TROUGH WILL BE OVER THE WEST
BECOMING REINFORCED AS MULTIPLE IMPULSES MOVE THROUGH WITHIN THE
FLOW, WITH SOME ENERGY POSSIBLY ACTING TO SUPPRESS THE EASTERN
RIDGE SLIGHTLY BY NEXT WEEKEND. SHOWERS AND THUNDERSTORMS WILL BE
MOST LIKELY ACROSS THE GULF COAST/FLORIDA REGION, THE SOUTHERN
ROCKIES, AND THE UPPER MIDWEST TO GREAT LAKES/NORTHEAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE OVERALL PATTERN HAS HAD PRETTY DECENT RUN TO RUN AGREEMENT WITH
THE SOME UNCERTAINTIES WITH THE TIMING/LOCATION OF AN UPPER LOW
FOR THE NORTHWEST AS VARIOUS SHORTWAVE ENERGIES FIRE THROUGH THE
TROUGH IN THE WEST. CONFIDENCE AND PREDICTABILITY REMAINS HIGH FOR
A LARGE UPPER RIDGE INITIALLY CENTERED OVER THE MID- MISSISSIPPI
VALLEY EARLY IN THE PERIOD BEFORE SLOWLY SHIFTING EASTWARD AND
WEAKENING SLIGHTLY BY THE END OF THE WEEK. BY LATE WEEK, THERE IS
SOME CONSENSUS FOR WESTERN U.S. ENERGY TO RIDE OVER THE TOP OF THE
EASTERN RIDGE, WHICH MAY ACT TO SUPPRESS IT SLIGHTLY. THE ECMWF
SEEMS LESS ENTHUSED WITH THIS SCENARIO, HANGING ONTO A STRONGER
RIDGE INTO THE WEEKEND. THE WPC FORECAST USED A COMPROMISE OF THE
DETERMINISTIC GUIDANCE EARLY ON, TRANSITIONING TO 60
DETERMINISTIC/40 GEFS AND EC ENSEMBLE MEANS.
..WEATHER/HAZARDS HIGHLIGHTS
THE MOST IMPACTFUL WEATHER HAZARD DURING THE MEDIUM RANGE PERIOD
WILL BE A LONG LASTING HEAT WAVE AFFECTING MUCH OF THE CENTRAL TO
EASTERN U.S. BEGINNING DURING THE SHORT RANGE PERIOD AND LASTING
THROUGH THE MEDIUM RANGE PERIOD. WIDESPREAD TEMPERATURES INTO THE
90S TO LOW 100S, COMBINED WITH HIGH HUMIDITY, WILL RESULT IN HEAT
INDICES APPROACHING OR EXCEEDING 105-110 IN MANY PLACES. THIS
EQUATES TO WIDESPREAD MAJOR TO EXTREME HEATRISK FROM THE MIDWEST/MS
VALLEY EASTWARD TO THE EAST COAST. OVERNIGHT LOWS WILL ALSO BE
QUITE WARM, WITH SOME RECORD HIGH MINIMUMS POSSIBLE, BRINGING
LITTLE TO NO RELIEF FROM THE HEAT IN THE NIGHTTIME HOURS.
RAIN AND THUNDERSTORMS WILL DEVELOP ASSOCIATED WITH A FRONTAL
SYSTEM ACROSS PARTS OF THE UPPER MIDWEST AND GREAT LAKES TUESDAY-
WEDNESDAY. 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. WHILE MUCH OF THIS SHOULD BE FAIRLY
PROGRESSIVE, MOISTURE ANOMALIES AND INSTABILITY MAY SUPPORT A
LOCALIZED FLASH FLOOD THREAT. WPC CONTINUES TO HIGHLIGHT PARTS OF
THE UPPER MIDWEST AND THE INTERIOR NORTHEAST WITH MARGINAL RISKS
ON BOTH THE DAY 4/TUESDAY AND DAY 5/WEDNESDAY EXCESSIVE RAINFALL
OUTLOOK.
ELSEWHERE, MOISTURE FUNNELING BETWEEN THE WESTERN TROUGH AND THE
EASTERN RIDGE SHOULD SUPPORT SHOWERS AND THUNDERSTORMS ACROSS PARTS
OF THE SOUTHERN ROCKIES AND SOUTHERN HIGH PLAINS FOR AT LEAST THE
EARLY PART OF THE WEEK. A MARGINAL RISK ERO REMAINS FOR DAY
4/TUESDAY. DIURNALLY DRIVEN SHOWERS AND STORMS ARE ALSO 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 LATE WEEK/NEXT WEEKEND AS THE UPPER RIDGE
SLIGHTLY WEAKENS AND UPPER LEVEL ENERGY TRIES TO INTRUDE 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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page