920
FXUS02 KWBC 070650
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
250 AM EDT MON SEP 7 2026
VALID 12Z THU SEP 10 2026 - 12Z MON SEP 14 2026
...PROLONGED LATE-SUMMER HEAT WAVE LINGERS FOR THE SOUTHERN PLAINS
THROUGH MUCH OF THE WEEK...
..OVERVIEW
TROUGHING WILL EXTEND ACROSS EASTERN CANADA INTO THE NORTHEAST
LATER THIS WEEK, BRINGING RAIN CHANCES ALONG THE COLD FRONT FROM
THE NORTHEAST INTO THE MID-MISSISSIPPI VALLEY ON THURSDAY.
MEANWHILE UPPER RIDGING WILL MAINTAIN HOT CONDITIONS ACROSS THE
SOUTH- CENTRAL U.S. THROUGH AT LEAST THE WORKWEEK, WITH SOME RELIEF
POSSIBLE, PARTICULARLY FOR NORTHERN AREAS AS THE TROUGH MOVES INTO
THE EAST. ANOTHER SHORTWAVE DIGS INTO THE NORTHWEST BY NEXT
WEEKEND, WITH MUCH MORE UNCERTAINTY ON ITS EASTWARD PROGRESSION
INTO THE NORTH-CENTRAL U.S. EARLY NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE STARTS IN GOOD AGREEMENT FOR THE FIRST HALF OF THE
PERIOD WITH ONLY MINOR TIMING DIFFERENCES WITH SYSTEMS. AS THE
FIRST TROUGH MOVES THROUGH THE EASTERN U.S. THURSDAY- FRIDAY, THIS
MAY SUPPRESS THE WARM RIDGE ACROSS THE SOUTHEAST AND CENTRAL PLAINS
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. A MULTI-MODEL BLEND WAS USED FOR THIS PART OF THE
PERIOD.
THE GREATEST UNCERTAINTY CONTINUES TO SURROUND THE EVOLUTION OF
ENERGY DIVING INTO THE NORTHWEST BY NEXT WEEKEND. THE TREND HAS
BEEN FOR MORE SEPARATION OF THIS SYSTEM WITH THE SECOND TROUGH
THROUGH CENTRAL CANADA. THIS NOW FAVORS A CLOSED UPPER LOW NEAR
BRITISH COLUMBIA ON FRIDAY AND OVER THE NORTHWEST ON SATURDAY.
THERE IS SOMEWHAT GOOD CONSENSUS ON THIS FEATURE, BUT HOW IT
EVOLVES DOWNSTREAM REMAINS HIGHLY UNCERTAIN. THE CMC AND THE EC-
AIFS TEND TO SHOW SOME COMBINATION OF THIS LOW WITH A MEANDERING
SECOND LARGE UPPER LOW WELL OFF THE WEST COAST, WHILE THE GFS AND
ECMWF KEEP THESE TWO FEATURES SEPARATE AND HAVE A FASTER
PROGRESSION OF THE TROUGH INTO THE NORTH-CENTRAL U.S. BY DAY 7 (GFS
FASTER THAN THE ECMWF). THE ENSEMBLES ALSO SHOW QUITE A BIT OF
SPREAD AND UNCERTAINTY, WHICH MAKES MODEL BLEND CHOICES
PARTICULARLY DIFFICULT. TENDED TO FAVOR THE ECMWF AND ECENS MEAN
SINCE THEY WERE CLOSEST TO PREVIOUS WPC CONTINUITY. THE NEW 00Z
GUIDANCE TONIGHT, INCLUDING THE CMC, SEEM TO BE TRENDING MORE
TOWARDS THE ECMWF SO THIS SEEMS LIKE A SAFE STARTING POINT FOR NOW.
..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 RELIEF TO ESPECIALLY NORTHERN
AREAS, CONFINING THE GREATEST HEAT THREAT TO MOSTLY THE SOUTHERN
PLAINS. ABOVE NORMAL HEAT MAY ALSO BUILD BRIEFLY ACROSS THE
SOUTHWEST AND PARTS OF CALIFORNIA EARLY PERIOD IN BETWEEN SYSTEMS.
AN UPPER AND SURFACE LOW MOVING THROUGH EASTERN CANADA WILL PUSH A
COLD FRONT THROUGH THE NORTHEAST/MID-ATLANTIC, OHIO VALLEY, AND
MID- MISSISSIPPI VALLEY INTO THURSDAY, WITH LOCALLY HEAVY RAIN
POSSIBLE. MOISTURE AND INSTABILITY WILL ALSO ALLOW FOR ROUNDS OF
DIURNALLY DRIVEN SCATTERED THUNDERSTORMS IN THE SOUTHEAST, AND
MONSOONAL MOISTURE CONTINUING FOR THE SOUTHWEST AND SOUTHERN
ROCKIES THROUGH MOST OF THE PERIOD. 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, WITH MODERATE TO LOCALLY HEAVY
RAIN POSSIBLE BUT HIGHLY UNCERTAIN AND DEPENDENT ON BOTH UPPER AND
SURFACE FRONT EVOLUTION ACROSS THE REGION.
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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