MESOSCALE PRECIPITATION DISCUSSION 0482
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
530 AM EDT THU JUL 13 2017

AREAS AFFECTED...NORTHERN & CENTRAL OH...NORTHWEST PA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 130930Z - 131430Z

SUMMARY...STRONG MOISTURE CONVERGENCE AND FLUX SUPPORTS HEAVY
RAINFALL ACROSS SATURATED GROUNDS LEADING TO FLASH FLOODING
CONDITIONS.

DISCUSSION...COMPACT MCV CURRENTLY TRACKING THROUGH NORTHEAST IND
CONTINUES TO PROVIDE EXCELLENT DPVA IN ADVANCE OF IT ACROSS
NORTHERN OHIO.  THIS ASCENT IS FURTHER SUPPORTED BY RIGHT ENTRANCE
REGION TO 70-80KT SPEED MAX CURRENTLY CROSSING N MI. THIS UPPER
LEVEL SUPPORT HAS LEAD TO A WEAK SURFACE INFLECTION IN SE MI WITH
A OUTFLOW BOUNDARY/EFFECTIVE COLD FRONT DRAPING SOUTHWARD ACROSS
NW OH AND TRAILING ACROSS E CENTRAL IND ATTM.  WEAK PSEUDO WARM
FRONT ALSO EXISTS AT INTERSECTION OF CONFLUENT 850MB FLOW BETWEEN
TOLEDO TO SANDUSKY EXTENDING EASTWARD FROM IT.
WAA ACROSS THIS CONFLUENCE ZONE HAS SPARKED CONVECTION AHEAD OF
MAIN ARC OF THUNDERSTORMS WITH EVEN NEW CELLS AS FAR EAST AS
PORTAGE COUNTY OH.

ALONG THE OUTFLOW BOUNDARY...STRONG MST CONVERGENCE AT THE NOSE OF
DEEP SATURATED PROFILES ACROSS NW OH WHERE TPWS HAVE RISEN TO
2.25".  THIS COMBINED WITH THE FLUX ALLOWS FOR HOURLY RAIN RATES
UP TO 2.5"/HR. FORWARD PROPAGATION DUE TO STRENGTH OF NEARLY
UNIDIRECTIONAL FLOW ACROSS N OHIO IS LIKELY TO LIMIT SOME OF THE
OVERALL RAIN TOTALS THOUGH PRECURSORY CELLS ALONG EFFECTIVE WARM
FRONT MAY ALLOW FOR REPEAT TRACKS.  AS SUCH HI-RES CAMS ARE
SUGGESTIVE OF 3-6 HOURLY TOTALS OF 2-4" ACROSS N OHIO; GIVEN
SATURATED SOILS AND LOWERED FFG (GENEARALLY BELOW 2"/3HRS) VALUES
DUE TO 400-600% OF NORMAL RAINFALL OVER THE LAST 7 DAYS PER
AHAPS/MRMS DATASETS FLASH FLOODING IS CONSIDERED LIKELY.

FURTHER SOUTH...THE TRAILING FRONTAL ZONE DUE TO SLOWER MID-LEVEL
STEERING FLOW WILL STALL GENERALLY FROM DAYTON TO COLUMBUS REGION
WHILE CONTINUED CONFLUENT LOW LEVEL FLOW SHOULD BE SUFFICIENT FOR
ENOUGH MOISTURE CONVERGENCE TO ALLOW FOR THE POSSIBILITY OF
ADDITIONAL CONVECTION THOUGH IT MAY BE A BIT MORE SCATTERED IN
NATURE.  ADDITIONALLY THERE WILL BE A GREATER POTENTIAL FOR
BACKBUILDING AS WELL AS TRAINING AS THE BOUNDARY FLATTENS TO BE
NEAR PARALLEL TO STEERING FLOW IF THE CONVECTION DOES INDEED
DEVELOP.  CONFIDENCE IS A BIT LESS HERE DUE TO THE CONTINGENCY OF
SUFFICIENT CONVERGENCE IN THE WAKE OF WEAKENING FLOW/EXITING
SHORTWAVE TO THE NORTHEAST.     

GALLINA

ATTN...WFO...CLE...ILN...PBZ...

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

LAT...LON   42287997 41967989 41187993 40638075 40178207
            39828312 39508426 39728462 40118441 40588370
            41158354 41508330 41858304 41638252 41568238
            41958133 42228055