677
FXUS02 KWBC 260632
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
231 AM EDT MON JUN 26 2023
VALID 12Z THU JUN 29 2023 - 12Z MON JUL 03 2023
...MAJOR EXTENDED HEAT WAVE TO FOCUS FROM TEXAS TO THE MID-LOWER
MISSISSIPPI VALLEY...
...EXCESSIVE RAINFALL THREAT ACROSS THE NORTHEAST AND THE CENTRAL
U.S. LATE WEEK...
..OVERVIEW WITH GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A
COMPOSITE BLEND OF WELL CLUSTERED MID-LARGER SCALE GUIDANCE FROM
THE 18 UTC GFS/GEFS MEAN, THE 12 UTC ECMWF/UKMET/CANADIAN AND
ECMWF ENSEMBLE MEAN ALONG WITH THE COMPATIBLE 01 UTC NATIONAL
BLEND OF MODELS. FORECAST CONFIDENCE IS BOLSTERED AT THESE SCALES.
WPC PRODUCT CONTINUITY IS ALSO REASONABLY WELL MAINTAINED IN THIS
FASHION AND THE FORECAST REMAINS IN LINE WITH A COMPOSITE OF NEWER
00 UTC CYCLE GUIDANCE. THE BROAD BLENDING OF COMPATIBLE GUIDANCE
TENDS TO MITIGATE SMALLER SCALE DIFFERENCES CONSISTENT WITH
PREDICTABILITY.
..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 (ESPECIALLY INTO FAVORED TERRAIN) IN THIS
SLOW-MOVING SYSTEM. A WPC EXCESSIVE RAINFALL OUTLOOK (ERO)
"MARGINAL RISK" AREA IS PLANNED TO LINGER OVER THE NORTHEAST
THURSDAY INTO EARLY FRIDAY IN AN AREA WITH ANTECEDENT RAINFALL
FROM A PREVIOUS SLOW-MOVING SYSTEM. ADDITIONAL LOW PRESSURE AND
ENHANCED RAINS WITH THE REMNANTS OF CINDY IS EXPECTED TO PASS TO
THE EAST FRIDAY/SATURDAY TOWARD THE CANADIAN MARITIMES.
MEANWHILE, THE EJECTION OF UPPER TROUGH ENERGIES OUT FROM THE
WEST/ROCKIES LATER WEEK IS EXPECTED TO BRING SCATTERED SHOWERS AND
STRONG TO SEVERE STORM CHANCES OUT ACROSS THE CENTRAL
PLAINS/VICINITY ALONG WITH LOCALLY HEAVY RAINFALL. THIS LENDS
ISSUANCE OF A "MARGINAL RISK" OF EXCESSIVE RAINFALL FOR THURSDAY
AND FRIDAY GIVEN HEIGHT FALLS/INSTABILITY AND POTENTIAL FOR
REPEAT/TRAINING OF CELLS. LATER, THE MAIN FOCUS FOR SHOWERS AND
THUNDERSTORMS WITH LOCALLY HEAVY DOWNPOURS SHOULD SHIFT TO THE
MID-MISSISSIPPI, OHIO AND TENNESSEE VALLEYS BEFORE SINKING
INCREASINGLY INTO THE SOUTH AND BROADLY EASTWARD ACROSS THE
EASTERN SEABOARD INTO THIS WEEKEND WITH APPROACH OF AN ORGANIZING
LOW AND LEAD/TRAILING FRONTAL SYSTEM, BUT DETAILS FOR LOCAL FOCUS
ARE LESS CERTAIN.
EXCESSIVE HEAT WILL CONTINUE TO PLAGUE THE SOUTH-CENTRAL U.S.
THROUGH THE HOLIDAY WEEKEND WITH EXPANSION NORTH AND EAST ACROSS
PORTIONS OF THE CENTRAL PLAINS AND THE MID-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. TEMPERATURE RECORDS ARE IN DANGER OF
BEING BROKEN DURING THIS SIGNIFICANT HEAT WAVE. THE DESERT
SOUTHWEST WILL ALSO EXPERIENCE TEMPERATURES WELL OVER 100 DEGREES,
BUT THAT IS NOT REALLY ANOMALOUS FOR THIS TIME OF YEAR. FLORIDA
WILL ALSO SEE HOT TO RECORD HIGH VALUES IN THIS PATTERN.
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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