647
FXUS02 KWBC 062000
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
400 PM EDT SUN SEP 6 2026
VALID 12Z WED SEP 09 2026 - 12Z SUN SEP 13 2026
...PROLONGED LATE-SUMMER HEAT WAVE LINGERS FOR THE CENTRAL/
SOUTHERN PLAINS TO THE MID/LOWER MISSISSIPPI VALLEY THROUGH MUCH OF
THE WEEK...
..OVERVIEW
TROUGHING WILL EXTEND FROM CANADA INTO THE NORTHERN TIER OF THE
U.S. LATER THIS WEEK, TRACKING FROM THE NORTHERN PLAINS/MIDWEST
THROUGH THE GREAT LAKES AND NORTHEAST WEDNESDAY-FRIDAY. THIS SHOULD
BRING RAIN CHANCES TO THESE AREAS SOUTH INTO THE MID-MISSISSIPPI
VALLEY, OHIO VALLEY, AND CENTRAL APPALACHIANS, WHILE PRIMARILY
DIURNALLY DRIVEN SCATTERED THUNDERSTORMS WILL CONTINUE ACROSS THE
SOUTHEAST. MEANWHILE UPPER RIDGING WILL MAINTAIN HOT CONDITIONS
ACROSS THE SOUTH-CENTRAL U.S. THROUGH THE WORKWEEK. SOME RELIEF IS
POSSIBLE BY NEXT WEEKEND, BUT THIS WILL DEPEND ON AN INCREASINGLY
UNCERTAIN PATTERN, INCLUDING THE TIMING AND PLACEMENT OF THE NEXT
UPPER TROUGH OR TWO COMING INTO THE NORTHWEST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE STARTS IN GOOD AGREEMENT WITH THE PATTERN DESCRIBED
ABOVE, AND A MULTI-MODEL BLEND OF THE DETERMINISTIC/AI GUIDANCE
WAS ABLE TO BE USED. AS THE FIRST TROUGH MOVES THROUGH THE EASTERN
U.S. THURSDAY-FRIDAY, THIS MAY SUPPRESS THE WARM RIDGE ACROSS THE
SOUTHEAST AS LEAST. THE NEXT TROUGH SHOULD REACH THE NORTHWESTERN
TO NORTH-CENTRAL U.S. EXTENDING FROM AN UPPER LOW IN CENTRAL CANADA
HUDSON BAY LATE WEEK. THIS LOW LOOKS TO MOVE OVER HUDSON BAY BY
THE WEEKEND WHILE THE TROUGHING MOVES ACROSS THE GREAT LAKES AND
NORTHEAST. THESE FIRST TWO TROUGHS MOSTLY SHOW MINOR MODEL
DIFFERENCES.
BY FAR, THE GREATEST MODEL SPREAD DURING THE PERIOD HAS BEEN WITH
THE EVOLUTION OF ENERGY DIVING THROUGH THE NORTHEAST
PACIFIC/WESTERN CANADA BY THE WEEKEND. SOME GUIDANCE INCLUDING THE
OLDER 00Z AND 06Z GFS RUNS WERE INDICATING THAT THIS ENERGY WOULD
BE JOINED UP WITH THE SECOND TROUGH, CAUSING IT TO DIG ACROSS THE
CENTRAL U.S. HOWEVER, MOST GUIDANCE (INCLUDING THE NEWER 12Z GFS)
IS NOW FAVORING THAT THIS ENERGY STAYS A SEPARATE FEATURE FROM THE
SECOND TROUGH, FORMING A CLOSED UPPER LOW NEAR BRITISH COLUMBIA
FRIDAY OR ATOP THE NORTHWEST BY SATURDAY (AKA A THIRD TROUGH OF THE
PERIOD). THIS UPPER LOW SHOWS SOMEWHAT BETTER CONSENSUS NOW WITH
THE 12Z CYCLE, THOUGH THE GFS IS STILL A LITTLE ON THE FAST SIDE.
HOWEVER, THE CMC AND EC-AIFS END UP SHOWING A MIDLATITUDE PACIFIC
LOW MOVING EAST TO COMBINE WITH THAT ENERGY, HOLDING IT FARTHER
WEST BY SUNDAY. THE FORECAST ATTEMPTED TO GO WITH A MIDDLE GROUND
FORECAST SOLUTION, MOST SIMILAR TO THE ECMWF AND EC MEAN.
..WEATHER/HAZARDS HIGHLIGHTS
THE LONG DURATION HEAT WAVE IS EXPECTED TO LINGER OVER THE
MID/LOWER MISSISSIPPI VALLEY TO SOUTHERN TEXAS THROUGH MUCH OF THE
WEEK WITH WIDESPREAD MAJOR TO EXTREME HEATRISK. KEY MESSAGES REMAIN
IN EFFECT WITH SEVERAL FORECAST RECORD MINIMUM AND MAXIMUM
TEMPERATURES FORECAST. THE PATTERN BECOMES MORE UNCERTAIN BY THE
WEEKEND, BUT THERE IS SOME TREND FOR WARM TEMPERATURES TO PERSIST
BECAUSE OF THE EVOLUTION OF THE UPPER TROUGHS FARTHER NORTH.
AN UPPER AND SURFACE LOW MOVING THROUGH SOUTHERN CANADA WILL PUSH
A COLD FRONT THROUGH THE NORTHEAST/MID-ATLANTIC, OHIO VALLEY, AND
MID-MISSISSIPPI VALLEY WEDNESDAY-THURSDAY, WITH LOCALLY HEAVY RAIN
POSSIBLE. ON THE BACKSIDE OF THE SYSTEM, HIGH WINDS COULD LINGER IN
THE NORTHERN PLAINS INTO WEDNESDAY. MOISTURE AND INSTABILITY WILL
ALSO ALLOW FOR ROUNDS OF DIURNALLY DRIVEN SCATTERED THUNDERSTORMS
IN THE SOUTHEAST EACH DAY. SOME MONSOONAL MOISTURE WILL CONTINUE
FOR THE SOUTHWEST AND SOUTHERN ROCKIES THROUGH THE PERIOD AS WELL.
THE UPPER TROUGHS IN THE NORTHWEST SHOULD ALSO ALLOW FOR ROUNDS OF
PRECIPITATION THERE BY FRIDAY AND INTO THE WEEKEND. SOME RAIN COULD
EXPAND ACROSS THE NORTH-CENTRAL U.S. NEXT WEEKEND, BUT THE
POTENTIAL FOR HEAVY AMOUNTS THERE HAS TRENDED DOWN GIVEN THE
OVERALL MODEL TRENDS FOR THE TROUGHING DESCRIBED ABOVE.
TATE/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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