663
FXUS02 KWBC 030711
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
311 AM EDT THU SEP 3 2026
VALID 12Z SUN SEP 06 2026 - 12Z THU SEP 10 2026
...DANGEROUS LATE-SUMMER HEAT CONTINUES FROM THE CENTRAL/SOUTHERN
PLAINS TO THE MID/LOWER MISSISSIPPI VALLEY INTO NEXT WEEK...
..OVERVIEW
A STRONG UPPER RIDGE WILL CONTINUE TO BE THE FOCUS FOR A LONG-
LASTING HEAT WAVE ACROSS THE SOUTH-CENTRAL U.S. WHILE A SLOW-MOVING
UPPER LOW WILL KEEP MUCH OF THE WESTERN U.S. COOLER THAN NORMAL
INTO NEXT WEEK. MEANWHILE, MONSOONAL AND GLANCING TROPICAL MOISTURE
MAY LEAD TO BRIEFLY HEAVY RAINFALL AND ISOLATED FLASH FLOODING
SUNDAY INTO MONDAY ACROSS PARTS OF THE SOUTHWEST. HEAVY RAINFALL
POTENTIAL MAY ALSO INCREASE ACROSS THE NORTH-CENTRAL U.S. EARLY
NEXT WEEK AS A STRENGTHENING LOW PRESSURE SYSTEM MOVES ACROSS THE
REGION.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS REMAIN IN GOOD OVERALL AGREEMENT TO START THE MEDIUM RANGE
PERIOD WITH CONTINUED TROUGHING ACROSS THE WESTERN U.S. AND EASTERN
U.S. WITH STRONG RIDGING IN BETWEEN. TOWARDS THE MIDDLE OF NEXT
WEEK, MODELS FAVOR THE TROUGH/UPPER LOW OVER THE PACIFIC NORTHWEST
TO EJECT EASTWARD INTO THE NORTHERN PLAINS AND SOUTH-CENTRAL
CANADA, LEADING TO SURFACE CYCLOGENESIS JUST NORTH OF THE
U.S./CANADA BORDER WHILE ALSO SUPPRESSING AND EXPANDING THE CENTRAL
U.S. RIDGE FARTHER TO THE SOUTH AND EAST. THERE REMAINS SOME
QUESTIONS AS TO THE DEGREE OF TROUGHING THAT LINGERS DOWNSTREAM
OVER THE EASTERN U.S. AS THIS ALL OCCURS, BUT CURRENT CONSENSUS
SEEMS TO FAVOR RISING HEIGHTS AND MORE ZONAL FLOW OVER THE
NORTHEAST. UPSTREAM, MODELS ARE ADVERTISING ANOTHER TROUGH/UPPER
LOW DEVELOPING ALONG OR JUST OFF THE WEST COAST BY WEDNESDAY AND
THURSDAY AS MORE ENERGY DIGS INTO THE EASTERN PACIFIC.
SOME UNCERTAINTY REMAINS WITH THE PRECIPITATION FORECAST ACROSS
SOUTHERN CALIFORNIA AND PARTS OF THE SOUTHWEST AND INTERMOUNTAIN
WEST SUNDAY INTO MONDAY AS THE DEGREE OF INFLUENCE FROM TROPICAL
MOISTURE REMAINS IN QUESTION. MODELS GENERALLY AGREE WITH A MORE
WESTWARD TRACK OF HURRICANE MARIE, LOSING MOST OF THE LAST
REMAINING BIT OF SUPPORT FOR A MORE NORTHERLY TRACK TOWARDS
SOUTHERN CALIFORNIA. HOWEVER, DESPITE A MORE WESTERLY TRACK, MODELS
DO STILL SUGGEST AT LEAST SOME GLANCING TROPICAL MOISTURE
ASSOCIATED WITH MARIE MAY GET DRAWN UP INTO THE MONSOONAL PLUME
LATE THIS WEEKEND INTO EARLY NEXT WEEK. WHAT MODELS DON'T YET AGREE
ON IS JUST HOW MUCH OF THAT MOISTURE WILL TRANSLATE TO SIGNIFICANT
PRECIPITATION, AS SOME ARE FAIRLY WET AND OTHERS NEARLY COMPLETELY
DRY. GIVEN THE UNCERTAINTY AND A RECENT DRIER TREND, DECIDED TO
KEEP THE FORECAST MORE CONSERVATIVE FOR NOW. THIS ALLOWS FOR A
LOWER END POPS AND PRECIPITATION AMOUNTS BUT WITH THE CAVEAT THAT
LOCALLY HEAVIER AND MORE WIDESPREAD AMOUNTS ARE NOT COMPLETELY
RULED OUT.
..WEATHER/HAZARDS HIGHLIGHTS
AN UNRELENTING AND INTENSE LATE-SUMMER HEAT WAVE WILL CONTINUE TO
BRING EXTREMELY HOT TEMPERATURES TO MUCH OF THE CENTRAL/SOUTHERN
PLAINS AND MID/LOWER MISSISSIPPI VALLEY THROUGH THE WEEKEND INTO
NEXT WEEK. HIGH TEMPERATURES WELL INTO THE 90S AND LOW 100S
COMBINED WITH HIGH HUMIDITY AND VERY WARM OVERNIGHT LOWS IN THE MID
70S WILL RESULT IN WIDESPREAD AREAS OF MAJOR TO EXTREME HEATRISK
AND A CONCERN FOR HEAT-RELATED ILLNESSES. SEE WPC'S KEY MESSAGES
FOR MORE DETAILS. MEANWHILE, COOLER TEMPERATURES AND LOWER HUMIDITY
IN THE WAKE OF A SEASONABLY STRONG COLD FRONT WILL CONTINUE TO
SETTLE INTO PARTS OF THE OHIO VALLEY, MID-ATLANTIC, AND SOUTHEAST
HEADING INTO LABOR DAY. COOLER THAN NORMAL TEMPERATURES WILL ALSO
PERSIST FOR MUCH OF THE WESTERN U.S. INTO EARLY NEXT WEEK AS
UNSETTLED WEATHER ASSOCIATED WITH A SLOW-MOVING UPPER LOW LINGERS
OVER THE REGION.
IN BETWEEN THE UPPER LOW ACROSS THE PACIFIC NORTHWEST AND THE
STRONG RIDGE OVER THE CENTRAL U.S., SOUTHWESTERLY FLOW WILL DRAW
MONSOONAL MOISTURE INTO PARTS OF THE SOUTHWEST AND INTERMOUNTAIN
WEST THIS WEEKEND INTO EARLY NEXT WEEK. THERE MAY BE A BRIEF AND
GLANCING TROPICAL ENHANCEMENT TO THE MONSOONAL MOISTURE COURTESY OF
HURRICANE MARIE PRIOR TO TRACKING FARTHER OUT TO SEA, WHICH COULD
LEAD TO A LOW BUT NON-ZERO FLASH FLOODING THREAT WITH ANY SHOWERS
AND THUNDERSTORMS THAT DEVELOP. WITH THAT BEING SAID, THERE STILL
REMAINS A FAIR AMOUNT OF SPREAD BETWEEN FORECAST PRECIPITATION
AMOUNTS, AND RECENT TRENDS HAVE BEEN DRIER. AS A RESULT, A MORE
CONSERVATIVE FORECAST APPROACH IS PRUDENT UNTIL DETAILS BECOME
CLEARER IN THE COMING DAYS.
THE POTENTIAL FOR WIDESPREAD SHOWERS AND THUNDERSTORMS WITH
LOCALLY HEAVY RAINFALL IS BECOMING MORE LIKELY FOR PARTS OF THE
NORTHERN ROCKIES, NORTHERN PLAINS AND UPPER MIDWEST LATE THIS
WEEKEND INTO EARLY NEXT WEEK AS A LOW PRESSURE SYSTEM MOVES
NORTHEAST ACROSS THE REGION. A SEVERE WEATHER THREAT IS ALSO
BECOMING MORE LIKELY ACROSS PORTIONS OF THE NORTHERN PLAINS AND
UPPER MIDWEST THANKS TO INCREASING MOISTURE AND INSTABILITY AHEAD
OF THIS STRENGTHENING STORM SYSTEM.
MILLER
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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