339
AWUS01 KWNH 032357
FFGMPD
PAZ000-MDZ000-VAZ000-DCZ000-WVZ000-OHZ000-040555-
MESOSCALE PRECIPITATION DISCUSSION 1190
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
756 PM EDT THU SEP 03 2026
AREAS AFFECTED...IN AND NEAR WV & PORTIONS OF THE MID-ATLANTIC
STATES
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 032355Z - 040555Z
SUMMARY...A COUPLE ROUNDS OF HEAVY RAINFALL COULD LEAD TO FLASH
FLOODING IN AND AROUND WV & PORTIONS OF THE MID-ATLANTIC STATES
OVER THE NEXT SEVERAL HOURS. HOURLY RAIN AMOUNTS TO 2.5" WITH
ADDITIONAL LOCAL TOTALS TO 4" ARE POSSIBLE THROUGH AT LEAST 05Z.
DISCUSSION...SHOWERS AND THUNDERSTORMS HAVE AT TIMES TRIED TO
ALIGN ACROSS SOUTHWEST PA AS OF LATE, WITH THE INITIAL CONVECTION
CARVING A NEW INSTABILITY GRADIENT ACROSS THE REGION FOR
CONVECTION BACK ACROSS FAR EASTERN OH TO FOLLOW. PRECIPITABLE
WATER VALUES ARE APPROACHING 2". EFFECTIVE BULK SHEAR IS ~40 KTS.
WITH CIN BEGINNING TO DEVELOP, MU CAPE IS ~3000 J/KG.
MUCIN THAT DEVELOPED IN THE WAKE OF MORNING CONVECTION ACROSS
PORTIONS OF THE MID-ATLANTIC STATES HAS BEEN STUBBORN/PERSISTENT
TODAY AND APPEARED TO HAVE SET UP A RELATIVE WALL THAT ORGANIZED
CONVECTION HAS HAD TROUBLE PASSING. THIS IS SEEN IN THE 18Z HREF
GUIDANCE, THOUGH THE 12Z REFS SHOWS A DIFFERENT EVOLUTION
ENTIRELY. A ZONE OF 850 HPA CONFLUENCE IS FORECAST TO SHIFT SOUTH
TO THE NATION'S CAPITAL OVER THE NEXT SEVERAL HOURS, WHICH COULD
GUIDANCE ANY REMAINING ACTIVITY IN THAT DIRECTION. WHILE THE 12Z
REFS IS MISSING THE BOAT ON THE HEAVY RAINFALL IN WESTERN NY AT
THE PRESENT TIME, A MESOCYCLONE IN SOUTHWEST PA IS ATTEMPTING TO
BREAK THROUGH THE MUCIN WALL AND EDGE TOWARDS THE MASON-DIXON
LINE. A COMPROMISE OF SORTS WAS USED TO ACCOUNT FOR THE ABOVE.
HOURLY RAIN AMOUNTS TO 2.5" WITH ADDITIONAL LOCAL TOTALS TO 4" ARE
POSSIBLE FOR AS LONG AS ORGANIZED CONVECTION CAN PERSIST, ANOTHER
CONCEPT WHICH THE MESOSCALE GUIDANCE CANNOT AGREE. HAVE USED A
06Z HORIZON WHICH IS CLOSER TO THE 18Z HREF TIMING OF CONVECTIVE
WANING. THERE IS MORE UNCERTAINTY THAN USUAL IN THIS
FORECAST/FUTURE CONVECTIVE EXPECTATIONS.
ROTH
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...CTP...LWX...PBZ...PHI...RLX...RNK...
ATTN...RFC...RHA...TIR...NWC...
LAT...LON 41257964 40207709 39247615 38487727 38138105
39548196 40608120
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