411
FXUS02 KWBC 251906
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SUN JUN 25 2023
VALID 12Z WED JUN 28 2023 - 12Z SUN JUL 02 2023
...PROLONGED HEAT WAVE FORECAST TO EXPAND FROM TEXAS TO THE
MID-LOWER MISSISSIPPI VALLEY...
...EXCESSIVE RAINFALL THREAT ACROSS THE NORTHEAST AND
NORTH-CENTRAL U.S. STATES MID-LATE WEEK...
..OVERVIEW WITH GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
MODELS REMAIN IN GENERAL AGREEMENT THAT A POSITIVELY-TILTED TROUGH
LIFTING OUT OF THE WESTERN U.S. INTO THE NORTH-CENTRAL U.S. WILL
SPREAD THE EXCESSIVE HEAT FROM OVER THE SOUTHERN PLAINS TOWARD THE
MID-MISSISSIPPI DURING THE LATTER HALF OF THIS WEEK. HOWEVER,
UNCERTAINTIES WITH THE DETAILS OF THE LIFTING TROUGH CONTINUE TO
SHIFT THE FOCUS OF AN AREA OF ENHANCED RAINFALL FARTHER EAST FROM
THE NORTHERN PLAINS TO THE UPPER MIDWEST MIDWEEK. MEANWHILE,
MODELS REMAIN IN VERY GOOD AGREEMENT TO KEEP A WEAKENING BUT
SLOW-MOVING TROUGH OVER NEW ENGLAND THROUGH LATE WEEK BEFORE THE
NEXT LOW PRESSURE WAVE MOVING ACROSS THE CENTRAL U.S. MAY REACH
NEW ENGLAND BY NEXT WEEKEND.
THEREFORE, THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY
DERIVED FROM A COMPOSITE BLEND OF THE 06Z GFS/00Z ECMWF/00Z
CANADIAN MODELS TOGETHER WITH THEIR ENSEMBLE MEANS. MORE OF THE
ENSEMBLE MEAN SOLUTIONS WERE INCLUDED FOR DAYS 6 AND 7 TO HANDLE
TO HIGHER UNCERTAINTY WITH THE TIMING OF THE TROUGH EJECTION
ACROSS THE NORTH-CENTRAL U.S. LATE NEXT WEEK. THIS SOLUTION
MAINTAINS GOOD WPC PRODUCT CONTINUITY EXCEPT THE SECONDARY FRONTAL
POSITION ACROSS THE NORTHERN PLAINS, AS WELL AS A SIGNIFICANT
EASTWARD SHIFT IN AN AREA OF ENHANCED RAINFALL ACROSS THE NORTHERN
PLAINS MIDWEEK.
..WEATHER/HAZARDS HIGHLIGHTS
AN AMPLIFIED TROUGH SLOWLY PROGRESSING THROUGH THE NORTHEAST WILL
WRAP ATLANTIC MOISTURE AROUND A GRADUALLY WEAKENING LOW PRESSURE
SYSTEM TO FUEL WIDESPREAD AND LINGERING PRECIPITATION. LOCALLY
HEAVY RAINFALL WILL BE POSSIBLE WITH POTENTIAL TRAINING AND
EMBEDDED THUNDERSTORMS IN THIS SLOW-MOVING SYSTEM. A WPC EXCESSIVE
RAINFALL OUTLOOK (ERO) "MARGINAL RISK" AREA IS MAINTAINED OVER THE
NORTHEAST FOR WEDNESDAY AND THURSDAY IN AN AREA WITH ANTECEDENT
RAINFALL FROM THE PREVIOUS SLOW-MOVING SYSTEM.
MEANWHILE, THE EJECTION OF UPPER TROUGH ENERGIES OUT FROM THE WEST
MIDWEEK IS EXPECTED TO BRING SCATTERED SHOWERS AND STORM CHANCES
EASTWARD ACROSS THE NORTHERN PLAINS INTO THE UPPER MIDWEST WITH
LOCALLY HEAVY RAINFALL. MODELS HAVE GENERALLY SPED UP THE
EASTWARD EJECTION OF THE UPPER ENERGIES, RESULTING IN AN EASTWARD
SHIFT IN A MARGINAL RISK OF EXCESSIVE RAINFALL INTO THE UPPER
MIDWEST ON WEDNESDAY. REMAINING ENERGIES FROM THE POSITIVELY
TILTED TROUGH IN THE WESTERN U.S. ARE FORECAST TO ORGANIZE ANOTHER
AREA OF MARGINAL RISK OF EXCESSIVE RAINFALL FROM THURSDAY INTO
EARLY FRIDAY OVER THE NORTHERN HIGH PLAINS. MEANWHILE, SCATTERED
SHOWERS WITH EMBEDDED THUNDERSTORMS AND LOCALLY HEAVY RAIN CAN BE
EXPECTED FROM THE CENTRAL U.S. TO THE EAST COAST DURING NEXT
WEEKEND WITH POSSIBLY AN AREA OF HEAVIER RAINFALL DEVELOPING OVER
NEW ENGLAND AHEAD OF A WARM FRONT AS A LOW PRESSURE WAVE IS
FORECAST TO MOVE FROM THE OHIO VALLEY TO THE LOWER GREAT LAKES.
IN TERM OF TEMPERATURES, EXCESSIVE HEAT WILL CONTINUE TO PLAGUE
THE SOUTH-CENTRAL U.S. INTO NEXT WEEK WITH A MID-WEEK EXPANSION
NORTH AND EAST ACROSS PORTIONS OF THE CENTRAL PLAINS AND INTO THE
MID- AND LOWER MISSISSIPPI VALLEY. THE HEAT WILL BE OPPRESSIVE
WITH WIDESPREAD HIGH TEMPERATURES EXCEEDING 100 DEGREES AND HEAT
INDICES AS HIGH AS 120 DEGREES. HEAT INDICES MAY EVEN EXCEED 120
DEGREES IN SOME LOCATIONS IN SOUTH TEXAS. SEVERAL TEMPERATURE
RECORDS ARE IN DANGER OF BEING BROKEN DURING THIS SIGNIFICANT HEAT
WAVE. THE DESERT SOUTHWEST WILL ALSO EXPERIENCE TEMPERATURES WELL
OVER 100 DEGREES NEXT WEEK, BUT THAT IS NOT REALLY ANOMALOUS FOR
THIS TIME OF YEAR. FLORIDA WILL ALSO SEE HOT TO RECORD HIGH VALUES.
KONG/SCHICHTEL
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, EXPERIMENTAL 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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