688
FXUS02 KWBC 090642
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
242 AM EDT WED SEP 9 2026
VALID 12Z SAT SEP 12 2026 - 12Z WED SEP 16 2026
...PROLONGED LATE-SUMMER HEAT WAVE LINGERS FOR THE SOUTHERN PLAINS
INTO EARLY NEXT WEEK...
..OVERVIEW
A SHORTWAVE WILL PUSH A COLD FRONT FROM THE UPPER MIDWEST TO THE
NORTHEAST THIS WEEKEND, WITH INCREASING RAIN CHANCES ALONG AND
AHEAD OF IT. BEHIND THIS, A COMPACT CLOSED LOW WILL 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. MEANWHILE, UPPER LEVEL RIDGING WILL PERSIST ACROSS THE
SOUTHERN TIER, MAINTAINING HOT CONDITIONS FOR MAINLY THE SOUTHERN
PLAINS AND MONSOONAL MOISTURE FOR THE SOUTHWEST. ANOTHER
POTENTIALLY DEEPER SHORTWAVE MOVES INTO THE NORTHWEST NEXT TUESDAY
OR WEDNESDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST MODEL GUIDANCE CONTINUES TO SHOW GOOD OVERALL AGREEMENT
ON THE LARGE SCALE PATTERN AND EVOLUTION THROUGH MOST OF THE
PERIOD, BUT PLENTY OF UNCERTAINTY IN THE DETAILS. THE MOST
IMPACTFUL SYSTEM WILL BE A CLOSED LOW OVER THE NORTHWEST THIS
WEEKEND, MOVING OVER THE NORTHERN ROCKIES AND PLAINS SUNDAY INTO
MONDAY. THIS PUSHES A STRONG COLD FRONT THROUGH THE NORTHERN TIER,
WITH GUIDANCE GENERALLY SHOWING BETTER AGREEMENT ON THE TIMING
COMPARED TO PRIOR RUNS. A GENERAL DETERMINISTIC MODEL COMPROMISE
SEEMED TO WORK WELL FOR THIS. DOWNSTREAM, A SHORTWAVE CLIPPING THE
GREAT LAKES CONTINUES TO SHOW MORE AMPLIFICATION OVER THE NORTHEAST
AND OFF THE EAST COAST THIS WEEKEND IN CMC RUNS (AND TO SOME
EXTENT THE EC-AIFS AS WELL) THAN THE CONSENSUS/ENSEMBLES WOULD
SUGGEST. BY NEXT TUESDAY OR WEDNESDAY, ANOTHER SHORTWAVE DROPS IN
THE PACIFIC NORTHWEST WITH NOTABLY MORE UNCERTAINTY. BOTH THE GFS
AND ECMWF ARE STRONGER SHOWING POSSIBLE CLOSED LOWS NEXT WEDNESDAY
OVER WASHINGTON, VS THE CMC AND EC-AIFS ARE A BIT MORE PROGRESSIVE
AND OPEN WITH THE WAVE. THE WPC FORECAST BLEND TRENDED MORE TOWARDS
THE ENSEMBLE MEANS BY DAYS 6 AND 7 TO HELP MITIGATE THESE
DIFFERENCES WILL MAY TAKE DAYS TO FULLY RESOLVE.
..WEATHER/HAZARDS HIGHLIGHTS
THE LONG DURATION HEAT WAVE IS EXPECTED TO LINGER OVER THE
SOUTHERN PLAINS AND AT TIMES INTO THE MID-MISSISSIPPI VALLEY
THROUGH THE MEDIUM RANGE WITH WIDESPREAD MAJOR TO EXTREME HEATRISK.
KEY MESSAGES REMAIN IN EFFECT WITH SEVERAL RECORD MINIMUM AND
MAXIMUM TEMPERATURES IN THE FORECAST. 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 LINGERING FRONT OVER THE SOUTHEAST AND MID-ATLATIC STATES WILL
CONTINUE A DAILY THREAT FOR SHOWERS AND THUNDERSTORMS, WITH LOCALLY
HEAVY RAIN. ANOTHER FRONT WILL BRING RAIN FROM THE CENTRAL U.S.
INTO THE NORTHEAST, WITH SOME ELEVATED FLASH FLOOD THREAT ACROSS
PARTS OF THE CENTRAL PLAINS TO MID-MISSISSIPPI VALLEY ON SATURDAY.
THE MAIN FOCUS FOR PRECIPITATION DURING THE PERIOD THOUGH 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 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. SHOWERS WILL MOVE WITH
THE FRONT INTO THE OHIO VALLEY AND NORTHEAST EARLY NEXT WEEK.
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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