389
FXUS02 KWBC 081850
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
250 PM EDT TUE SEP 8 2026
VALID 12Z FRI SEP 11 2026 - 12Z TUE SEP 15 2026
...PROLONGED LATE-SUMMER HEAT WAVE LINGERS FOR THE SOUTHERN PLAINS
THROUGH NEXT WEEKEND...
..OVERVIEW
A SHORTWAVE WILL PUSH A COLD FRONT FROM THE NORTHERN PLAINS TO THE
NORTHEAST FRIDAY TO SUNDAY, WITH INCREASING RAIN CHANCES ALONG AND
AHEAD OF IT. BEHIND THIS, CONSENSUS IS INCREASING FOR A COMPACT
CLOSED LOW TO MOVE INTO THE NORTHWEST BY SATURDAY, PROGRESSING
EASTWARD INTO THE NORTHERN PLAINS BY MONDAY. MODERATE TO HEAVY
RAINFALL LOOKS INCREASINGLY LIKELY ACROSS THE UPPER MISSISSIPPI
VALLEY TO GREAT LAKES SUNDAY AND MONDAY, WITH SOME WINTER WEATHER
POTENTIAL FOR THE NORTHERN ROCKIES. UPPER LEVEL RIDGING WILL
MEANWHILE PERSIST ACROSS THE SOUTHERN TIER, MAINTAINING HOT
CONDITIONS FOR THE SOUTH-CENTRAL U.S. AND MONSOONAL MOISTURE FOR
THE SOUTHWEST. ANOTHER SHORTWAVE MOVES INTO THE NORTHWEST NEXT
TUESDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST MODEL GUIDANCE REMAINS GENERALLY WELL CLUSTERED WITH A
PATTERN FEATURING A PROGRESSIVE NORTHERN STREAM THIS WEEKEND AND
AND INTO EARLY NEXT WEEK. FOLLOWING THE DEPARTURE OF AN INITIAL
UPPER-TROUGH/SURFACE COLD FRONT OFF THE EAST COAST MID- TO LATE
WEEK, ANOTHER UPPER-WAVE IS EXPECTED TO PASS ACROSS SOUTHERN CANADA
AND THE NORTHERN TIER BRINGING A COLD FRONT THROUGH THE
NORTHER/CENTRAL PLAINS AND MIDWEST AND TO THE NORTHEAST LATE THIS
WEEK AND THROUGH THE WEEKEND. THE PROGRESSION OF THIS FEATURE IS
WELL CAPTURED ON A BROADER SCALE BY ALL THE GUIDANCE. THEREAFTER,
GUIDANCE BEGINS TO DIVERGE A BIT HANDLING THE NEXT UPPER-WAVE
UPSTREAM DROPPING SOUTHWARD FROM THE NORTHEASTERN PACIFIC AND
AMPLIFYING/CLOSING OFF OVER THE NORTHWESTERN U.S. THE UKMET WAS
MORE PROGRESSIVE AND THE AIGFS SLOWER WHILE THE ECMWF/GFS/ECMWF
AIFS/CMC INITIALLY REMAIN BETTER CLUSTERED LATE WEEKEND. THE
PROGRESSION OF THE ECMWF/GFS/ECMWF AIFS/CMC BEGIN TO DIVERGE A BIT
MORE AS THE SYSTEM MOVES OUT ONTO THE PLAINS AND TO THE MIDWEST,
THOUGH REMAIN REASONABLY WELL CLUSTERED INTO EARLY NEXT WEEK AND
WITHIN THE ENVELOPE OF THE MEANS ESPECIALLY AT THIS LATER TIME
RANGE. SMALLER-SCALE DIFFERENCES ON BOUNDARY PLACEMENT WILL IMPACT
THE TIMING/FOOTPRINT OF QPF THOUGH MUCH OF THE GUIDANCE WAS IN
AGREEMENT ON POTENTIALLY VERY HEAVY RAINFALL. MEANWHILE, THE UPPER-
WAVE DOWNSTREAM BEGINS TO AMPLIFY ALONG/OFF THE EAST COAST BY
TUESDAY PARTICULARLY IN THE CMC BUT ALSO SOMEWHAT IN THE ECMWF
AIFS, WHICH WOULD POTENTIALLY BRING COOLER TEMPERATURES DOWN THE
EAST COAST, THOUGH THE GFS/ECMWF AND ENSEMBLE MEANS DON'T SHOW SUCH
A DEGREE OF AMPLIFICATION. THE UPDATED WPC FORECAST USED A
COMPOSITE BLEND OF THE DETERMINISTIC AND AI GUIDANCE THROUGH THE
FIRST PART OF THE PERIOD GIVEN THE NOTED GOOD AGREEMENT. THE UKMET
AND THEN AIGFS AND CMC ARE REMOVED AS THEIR SOLUTIONS DIVERGE
RELATIVE TO THE SECOND NOTED UPPER-WAVE AS WELL AS THE DOWNSTREAM
AMPLIFICATION OF THE FIRST UPPER-WAVE ALONG THE EAST COAST. A
CONTRIBUTION FROM THE ECENS AND GEFS MEANS REPLACED THIS GUIDANCE
WITH THE OTHER DETERMINISTIC GUIDANCE FALLING WITHIN THIS ENVELOPE.
THE NBM WAS A GOOD STARTING POINT FOR THE FORECAST GRIDS WITH ONLY
SOME MINOR MODIFICATIONS MADE TO REDUCE SOME HIGHER QPF AMOUNTS IN
THE LATE SATURDAY TO LATE SUNDAY TIME FRAME WHERE ONLY THE GFS WAS
PARTICULARLY AGGRESSIVE WITH AMOUNTS EARLY IN THE APPROACH OF THE
NORTHERN TIER SYSTEM THIS WEEKEND.
..WEATHER/HAZARDS HIGHLIGHTS
THE LONG DURATION HEAT WAVE IS EXPECTED TO LINGER OVER THE
MID/LOWER MISSISSIPPI VALLEY AND SOUTHERN PLAINS INTO THE MEDIUM
RANGE PERIOD WITH WIDESPREAD MAJOR TO EXTREME HEATRISK. KEY
MESSAGES REMAIN IN EFFECT WITH SEVERAL RECORD MINIMUM AND MAXIMUM
TEMPERATURES IN THE FORECAST. THERE CONTINUES TO BE A TREND FOR
RELIEF TO NORTHERN AREAS BY THE WEEKEND, CONFINING THE GREATEST
HEAT THREAT TO THE SOUTHERN PLAINS. ABOVE NORMAL HEAT MAY ALSO
BUILD BRIEFLY ACROSS THE SOUTHWEST AND PARTS OF CALIFORNIA INTO
LATE WEEK AS UPPER LEVEL RIDGING EXTENDS INTO THE REGION. THIS
SOUTHERN RIDGE WILL ALSO HELP SUPPORT MONSOONAL MOISTURE AND DAILY
SHOWER AND THUNDERSTORM CHANCES FOR THE FOUR CORNERS REGION MUCH OF
THE PERIOD. THERE LOOKS TO BE AN UPTICK IN THE INFLUX OF MOISTURE
EARLY NEXT WEEK AS THE SOUTHERN RIDGE SHIFTS EASTWARD WITH A
GREATER CHANCE FOR LOCALLY HEAVY RAINFALL/FLASH FLOODING.
A COLD FRONT WILL BE EXITING THE NORTHEAST BY FRIDAY, BUT LINGERS
ACROSS THE SOUTHEAST SUPPORTING DAILY SHOWERS AND THUNDERSTORMS,
WITH LOCALLY HEAVY RAINFALL POSSIBLE. BEHIND THIS, ANOTHER FRONT
WILL BRING RAIN TO THE MIDWEST AND INTO THE NORTHEAST FRIDAY-
SUNDAY. SEVERE WEATHER WILL BE POSSIBLE WITH STORMS FROM THE
CENTRAL PLAINS TO THE UPPER MIDWEST FRIDAY. THE MAIN FOCUS FOR
PRECIPITATION DURING THE PERIOD WILL BE ACROSS THE NORTHWEST INTO
THE NORTHERN U.S. THIS WEEKEND AND EARLY NEXT WEEK AS AN UPPER LOW
MOVES THROUGH. A STRONG COLD FRONT WILL ENHANCE RAINFALL CHANCES
AHEAD OF IT, WITH MODERATE TO HEAVY RAINFALL POTENTIAL INCREASING
BY SATURDAY BUT ESPECIALLY INTO SUNDAY AND MONDAY ACROSS PORTIONS
OF THE PLAINS INTO THE MIDWEST. WINTRY WEATHER WILL ALSO BE
POSSIBLE IN THE NORTHERN ROCKIES THIS COMING WEEKEND AS COOLER AIR
MOVES IN BEHIND THE COLD FRONT.
PUTNAM/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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