628
FXUS02 KWBC 092000
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
400 PM EDT TUE JUN 9 2026
VALID 12Z FRI JUN 12 2026 - 12Z TUE JUN 16 2026
...SIGNIFICANT HEAT WAVE CULMINATES FRIDAY IN THE EAST WITH HOT
CONDITIONS EXTENDING INTO THE SOUTH-CENTRAL U.S. THROUGH SUNDAY...
...HEAT BUILDING ACROSS THE WEST THIS WEEKEND INTO EARLY NEXT
WEEK...
...MULTI-DAY HEAVY RAINFALL THREAT IN SOUTHERN/CENTRAL PARTS OF THE
PLAINS AND MISSISSIPPI VALLEY...
..OVERVIEW
A BROAD UPPER TROUGH WITH EMBEDDED SHORTWAVES WILL BE PRESENT
ACROSS THE NORTHWESTERN TO NORTH-CENTRAL TIER OF THE U.S. AS THE
MEDIUM RANGE PERIOD BEGINS FRIDAY, GRADUALLY PUSHING EAST AND
RELOADING OVER THE WEEKEND INTO NEXT WEEK. AHEAD OF THE TROUGH,
HEAT IS FORECAST TO SURGE ACROSS THE EAST PARTICULARLY ON FRIDAY,
WHILE THE SOUTHERN TIER REMAINS HOT AND HUMID AS WELL. OVER THE
WEEKEND AND EARLY NEXT WEEK, UPPER RIDGING BUILDING IN THE WEST
BEHIND THE TROUGH WILL LEAD TO WARM TO HOT TEMPERATURES THERE.
PRECIPITATION-WISE, A FRONT IS FORECAST TO MEANDER ON THE
SOUTHERN/EASTERN SIDE OF THE TROUGH AND FOCUS MOISTURE FOR RAIN AND
THUNDERSTORMS. HEAVY RAINFALL IS POSSIBLE WITH MULTIPLE ROUNDS OF
STORMS EXPECTED TO SET UP IN THE SOUTHERN/CENTRAL PLAINS AND
LOWER/MID-MISSISSIPPI VALLEY OVER THE WEEKEND INTO EARLY NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST 00/12Z MODEL GUIDANCE REMAINS IN GOOD AGREEMENT ON THE
OVERALL PATTERN THROUGH MOST OF THE PERIOD. THE UPPER-RIDGE IN
PLACE OVER THE CENTRAL TO EASTERN U.S. THAT IS ONE OF THE MAIN
WEATHER STORIES THIS WEEK WILL BEGIN TO SHIFT EASTWARD AND WEAKEN
FROM THE WEST AS AN UPPER-TROUGH IMPINGES IT OVER THE CENTRAL U.S.
ADDITIONAL ROUNDS OF UPPER-ENERGY EMANATING FROM AN UPPER-LOW OVER
CENTRAL CANADA WILL HELP TO DEEPEN/BROADEN THIS UPPER-TROUGH OVER
THE CENTRAL TO EASTERN U.S., BRINGING COOLER TEMPERATURES WHILE
MAINTAINING AN ACTIVE AND STORMY PATTERN PARTICULARLY ACROSS THE
SOUTHERN TIER. MEANWHILE, AN UPPER-RIDGE WILL BEGIN TO BUILD ALONG
THE WEST COAST SHIFTING THE FOCUS OF EARLY SUMMER HEAT FROM THE
EAST COAST TO THE WESTERN U.S. OVER THE WEEKEND. GUIDANCE BEGINS TO
DIVERGE SPECIFICALLY WITH ONE EMBEDDED SHORT-WAVE DEPICTED TO DROP
SOUTHWARD THROUGH THE NORTHERN/CENTRAL ROCKIES AND EVENTUALLY OVER
THE PLAINS, WITH THE GFS MOST AGGRESSIVE IN BRINGING THIS WAVE
EASTWARD FASTER WITH A PROMINENT DEVELOPING SURFACE LOW. ON THE
OTHER HAND, THE ECMWF IS SLOWER AND REMAINS FURTHER WEST WITH ITS
PROGRESSION, WITH THE ECMWF AIFS IN BETWEEN. THE ENSEMBLE MEANS NOT
SURPRISINGLY SHOW LESS DETAIL BUT TEND TO FAVOR A SLOWER MIDDLE-
GROUND IN THE OVERALL UPPER-TROUGH POSITIONING, WITH THE ECMWF
FALLING MOST FAVORABLY WITHIN THIS ENVELOPE (THE NOTED DETAIL OF A
DEVELOPING SURFACE LOW IS ALSO ABSENT). THE CMC IS INITIALLY FASTER
BUT THE WAVE SHEARS OUT SO THE SURFACE REFLECTION IS MORE IN LINE
WITH THE ECMWF AND ENSEMBLE MEANS. THE SLOWER WAVE ALSO IMPACTS THE
STRENGTH OF THE WESTERN RIDGE PARTICULARLY WITH NORTHERN EXTENT
LEAVING SOME UNCERTAINTY WITH FORECAST TEMPERATURES. DESPITE THE
GENERALLY LESS PREDICTABLE UPPER-ENERGY AND WAVY FRONTAL BOUNDARIES
AT THE SURFACE, A GENERAL STORMY AND POTENTIALLY VERY WET PATTERN
LOOKS TO SET UP OVER THE SOUTH-CENTRAL TO SOUTHEASTERN U.S. AS THE
MEAN UPPER-FLOW SHIFTS SOUTHWARD. FURTHER NORTH, PRECIPITATION IS
LESS PREDICTABLE DUE TO UNCERTAINTY WITH THE NOTED SHORTWAVE.
THE UPDATED WPC FORECAST USED A COMPOSITE BLEND OF THE ECMWF/ECMWF
AIFS/GFS/CMC/UKMET FOR THE EARLY TO MIDDLE PART OF THE PERIOD
GIVEN GOOD OVERALL AGREEMENT ON THE PATTERN. THE FORECAST BLEND
SHIFTED AWAY FROM THE GFS, AND THEN THE ECMWF AIFS/CMC TOWARDS THE
END OF THE PERIOD AS GUIDANCE BEGINS TO DIVERGE, FAVORING THE ECMWF
WHICH MORE FAVORABLY LINED UP WITH INCREASING CONTRIBUTIONS FROM
THE ECENS/GEFS MEANS.
..WEATHER/HAZARDS HIGHLIGHTS
A FRONTAL BOUNDARY IS FORECAST TO STRETCH ACROSS THE INTERIOR
NORTHEAST SOUTHWESTWARD ACROSS THE OHIO VALLEY TO MID-SOUTH AND
BACK INTO THE SOUTH-CENTRAL PLAINS ON FRIDAY. THE FRONT WILL FOCUS
MOISTURE AND INSTABILITY FOR THUNDERSTORM CHANCES ALONG THE
BOUNDARY. SOME LOCALLY HEAVY RAIN COULD CAUSE ISOLATED FLASH
FLOODING, SO A MARGINAL RISK REMAINS IN PLACE FOR THE DAY 4/FRIDAY
ERO. BY SATURDAY, THE FRONT SHOULD CLEAR PRECIPITATION OUT OF THE
NORTHEAST, BUT IS FORECAST TO STALL AND MEANDER ACROSS THE CENTRAL
U.S. WITH A WEST-EAST ORIENTATION. A STRENGTHENING LOW LEVEL JET
WILL INCREASE INSTABILITY AND MOISTURE WHILE A SHORTWAVE ALOFT
HELPS PROVIDE LIFT IN THE SOUTH-CENTRAL U.S. WHERE THE FRONT SETS
UP. WITH THE INGREDIENTS FOR HEAVY RAINFALL/FLASH FLOODING IN
PLACE, A SLIGHT RISK IS OUTLOOKED FOR THE
OKLAHOMA/KANSAS/MISSOURI/ARKANSAS INTERSECTION. SOME OF THESE AREAS
HAVE WET ANTECEDENT CONDITIONS, OR SHOULD BY THAT TIME, AND
DETERMINISTIC GUIDANCE CONTINUES TO TREND UPWARD IN DEPICTING THE
THREAT OF SEVERAL INCHES OF RAINFALL. THIS FRONT IS FORECAST TO
LINGER AND ONLY GRADUALLY PRESS SOUTH INTO EARLY NEXT WEEK, SO
ADDITIONAL FLOOD RISKS ARE POSSIBLE ESPECIALLY IF ROUNDS OF RAIN
REPEAT OVER SIMILAR AREAS. FARTHER EAST, SCATTERED THUNDERSTORMS
THAT TEND TO BE DIURNALLY DRIVEN ARE LIKELY IN THE SOUTHEAST
(INCLUDING FLORIDA) FOR MULTIPLE DAYS. RAIN CHANCES MAY INCREASE
EARLY NEXT WEEK ACROSS THE OHIO VALLEY INTO THE MID- ATLANTIC AND
NORTHEAST, BUT WITH PLENTY OF QUESTIONS IN THE DETAILS. ELSEWHERE,
THE NORTHERN ROCKIES AND HIGH PLAINS COULD SEE SOME PRECIPITATION
LATE FRIDAY INTO SATURDAY, DEPENDENT ON THE EVOLUTION OF SHORTWAVE
ENERGY.
THE MEAN UPPER-LEVEL RIDGE OVER THE EASTERN U.S. IS EXPECTED TO
BRING THE FIRST SIGNIFICANT HEAT OF THE SUMMER INTO LATE WEEK, AS
TEMPERATURES REACH 10-15 DEGREES ABOVE AVERAGE. THE HEAT LOOKS TO
REACH ITS PEAK ACROSS THE MID-ATLANTIC AND NORTHEAST ON FRIDAY, AND
SEVERAL RECORD HIGHS AND RECORD WARM MINIMUM TEMPERATURES COULD BE
SET, BEFORE GRADUALLY MODERATING BY THE WEEKEND. SEE WPC'S KEY
MESSAGES FOR MORE. SUBTROPICAL RIDGING ACROSS THE SOUTHERN TIER
WILL YIELD HOT CONDITIONS THERE AS WELL THROUGH THE WEEKEND,
GENERALLY A FEW DEGREES ABOVE ALREADY WARM AVERAGES. THE DESERT
SOUTHWEST CAN EXPECT TEMPERATURES WELL INTO THE 100S AND PERHAPS
OVER 110, WHILE HEAT INDICES SHOULD BE OVER 100 IN THE SOUTHERN
PLAINS TO LOWER MISSISSIPPI VALLEY. INTO EARLY NEXT WEEK, HEAT AND
HUMIDITY SHOULD EASE A BIT IN PARTS OF THE SOUTH AS THE UPPER
TROUGH DIGS A BIT. BUT UPPER RIDGING BEHIND IT WILL LIKELY STRETCH
WARM TEMPERATURE ACROSS THE WEST COAST, WHICH COULD BE WELL ABOVE
AVERAGE PARTICULARLY IN THE PACIFIC NORTHWEST.
PUTNAM/TATE
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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