347
AWUS01 KWNH 041511
FFGMPD
PAZ000-MDZ000-WVZ000-OHZ000-MIZ000-INZ000-042110-
MESOSCALE PRECIPITATION DISCUSSION 1196
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1110 AM EDT FRI SEP 04 2026
AREAS AFFECTED...PORTIONS OF THE SOUTHERN GREAT LAKES...UPPER OH
VALLEY AND CENTRAL APPALACHIANS
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 041510Z - 042110Z
SUMMARY...ISOLATED TO SCATTERED AREAS OF FLASH FLOODING WILL BE
POSSIBLE GOING INTO THE AFTERNOON HOURS AS ADDITIONAL ROUNDS OF
SHOWERS AND THUNDERSTORMS IMPACT PORTIONS OF THE SOUTHERN GREAT
LAKES, UPPER OH VALLEY, AND CENTRAL APPALACHIANS.
DISCUSSION...THE LATEST RADAR AND SATELLITE IMAGERY SHOWS AN
ELONGATED AND BROKEN AXIS OF LOCALLY HEAVY SHOWERS AND
THUNDERSTORMS CROSSING THROUGH SOUTHERN LOWER MI AND DOWN THROUGH
NORTHEAST OH. THE CONVECTION IS ASSOCIATED WITH PROXIMITY OF A
FRONTAL ZONE ALONG WITH A WAVE OF LOW PRESSURE ADVANCING EAST
ALONG IT.
OVER THE NEXT SEVERAL HOURS, A COMBINATION OF DAYTIME
HEATING/BOUNDARY LAYER DESTABILIZATION ALONG WARM AIR ADVECTION
AND MOISTURE TRANSPORT INTO THIS FRONT SHOULD FAVOR REGIONAL AREAS
OF REDEVELOPING AND EXPANDING CONVECTION. THIS SHOULD ESPECIALLY
BE THE CASE ACROSS THE UPPER OH VALLEY AND CENTRAL APPALACHIANS
WITH AN EMPHASIS ON EASTERN OH. WESTERN PA AND NORTHERN WV WHERE
GREATER INSTABILITY PROFILES WITH MLCAPE VALUES INCREASING TO 1500
TO 2500+ ARE EXPECTED. AREAS OF OROGRAPHIC ASCENT INTO THE TERRAIN
WILL ALSO BE A PLAYER IN SUPPORTING CONVECTIVE INITIATION.
MODERATE TO STRONG INSTABILITY BY MID-AFTERNOON COUPLED WITH PWS
OF 1.5 TO 1.75 INCHES AND AT LEAST MODERATE VERTICAL SHEAR SHOULD
SUPPORT SOME STORM ORGANIZATION AND AREAS OF HIGH RAINFALL RATES
CAPABLE OF REACHING 1 TO 2 INCHES/HOUR. SOME REPEATING/TRAINING
CELL-ACTIVITY WILL BE EXPECTED AT LEAST LOCALLY, AND THIS WILL
SUPPORT SOME SOME STORM TOTALS OF 2 TO 3+ INCHES. THIS IS
GENERALLY SUPPORTED BY A CONSENSUS OF THE 12Z CAM GUIDANCE.
THE FFG VALUES ARE RATHER LOW ACROSS EASTERN OH, NORTHERN WV AND
ESPECIALLY WESTERN PA, WITH ELEVATED STREAMFLOWS NOTED IN THE
LATEST USGS STREAMFLOW DATA. THESE MORE SENSITIVE SOIL CONDITIONS
WILL INCREASE THE CONCERN FOR ADDITIONAL AREAS OF FLASH FLOODING
GOING INTO THE AFTERNOON HOURS. THE OVERALL THREAT WILL TEND TO BE
ISOLATED TO SCATTERED IN NATURE, BUT WILL ALSO INCLUDE AT LEAST
LOCALIZED URBAN FLASH FLOODING CONCERNS.
ORRISON
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...CLE...CTP...DTX...GRR...ILN...IWX...LWX...PBZ...
RLX...RNK...
ATTN...RFC...MSR...RHA...TIR...NWC...
LAT...LON 42818646 42798493 42378267 41708007 40637885
39357898 38138015 38208168 39258263 40028321
40968436 41578603 42018668
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