MESOSCALE PRECIPITATION DISCUSSION 0465
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
344 PM EDT TUE JUL 11 2017

AREAS AFFECTED...SOUTHEAST OH & SOUTHWEST PA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 111943Z - 120113Z

SUMMARY...THUNDERSTORMS NEAR THE OH/WV/PA BORDER JUNCTION COULD
LEAD TO HOURLY RAIN RATES UP TO 1.75" WITH LOCAL AMOUNTS TO 3".

DISCUSSION...THUNDERSTORMS ARE GROWING IN COVERAGE ACROSS
SOUTHEAST OH, THE NORTHERN WV PANHANDLE, AND SOUTHWEST PA IN THE
VICINITY OF A WEAK THERMAL BOUNDARY.  A PAIR OF MCVs ARE EVIDENT
ON RADAR IMAGERY NEAR THE SOUTHERN BORDER OF OH/IN.  INFLOW AT 850
IS SLIGHTLY CONVERGENT AND NEAR 20 KTS, NEAR THE MAGNITUDE OF THE
850-400 MEAN WIND.  EFFECTIVE BULK SHEAR OF 20-25 KTS EXIST HERE
PER SPC MESOANALYSES.  MLCAPE VALUES ARE 1000-2000 J/KG. 
PRECIPITABLE WATER VALUES AT 14Z WERE NEAR 1.5" PER GPS VALUES,
AND RECENT RAP RUNS INDICATE A FURTHER INCREASE SINCE THEN.

RAP FORECAST FIELDS INDICATE SOME INCREASE IN LOW-LEVEL INFLOW IS
EXPECTED AS THE MCVs APPROACH, PERHAPS EXCEEDING THE MEAN LAYER
WIND BY 50%, WHICH WOULD AID PRECIPITATION EFFICIENCY.  HOURLY
RAIN RATES UP TO 1.75" IS EXPECTED BASED ON THE AVAILABLE MOISTURE
AND INSTABILITY.  THE MESOSCALE GUIDANCE SHOWS A WIDELY SCATTERED
SIGNAL FOR HEAVY RAIN AMOUNTS, WITH AN AGREEABLE SIGNAL FOR LOCAL
AMOUNTS OF 3", PARTICULARLY NEAR EASTERNMOST OH AND SOUTHWEST PA. 
THE UPTICK IN CONVECTION AND HEAVY RAIN COULD CONTINUE UNTIL 01Z
BEFORE FADING THEREAFTER, BASED ON THE SIGNAL IN THE 06Z SSEO
NEIGHBORHOOD PROBABILITIES. THE EFFECTIVE FRONT/THERMAL BOUNDARY
COULD SAG A LITTLE TO THE SOUTH, WHICH WAS ACCOUNTED FOR IN THE
AREA DEPICTED.  CONSIDERING SATURATED SOILS AND SOME RUGGED
TOPOGRAPHY IN THIS REGION, FLASH FLOODING IS A CONCERN.

ROTH

ATTN...WFO...CLE...CTP...ILN...LWX...PBZ...RLX...

ATTN...RFC...MARFC...OHRFC...

LAT...LON   41348324 41258100 40117841 39097852 38827977
            39608218