MESOSCALE PRECIPITATION DISCUSSION 0479
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
157 AM EDT THU JUL 13 2017

AREAS AFFECTED...NORTHERN IND...NOTHERN OH...NORTHEAST IL

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

VALID 130600Z - 131100Z

SUMMARY...INCREASING CONVECTIVE COVERAGE THROUGH AREA OF SATURATED
SOILS LEAD TO POSSIBLE FLASH FLOODING IN THE EARLY MORNING.

DISCUSSION...GOES-E/16 WV LOOP DENOTES SPEED MAX/ANTICYCLONICALLY
CURVED JET ENTRANCE REGION ACROSS N MI ATTM BECOMING A BIT TIGHTER
ALLOWING FOR INCREASED EVACUATION.  AT THE LOWER LEVELS AN OUTFLOW
BOUNDARY/EFFECTIVE COLD FRONT ASSOCIATED WITH WEAK DPVA IS
SUPPORTING DEVELOPMENT FROM S OF IKK THROUGH SOUTHERN LAKE
MICHIGAN.  ADDITIONALLY...AHEAD OF THE BOUNDARY STRENGTHENING LLJ
FROM SSW IS SUPPORTING WAA REGIME WITH MODEST SPEED CONVERGENCE
ACROSS NE IND ATTM.  ON THE WESTERN PERIPHERY OF THIS
JET...CONFLUENCE FROM WESTERLY 850MB FLOW SUPPORTS CONVERGENCE TO
DEVELOP E-W SLIGHTLY ARCHED LINE OF DEEP CONVECTION DENOTED WITH
OVERSHOOTING TOPS BELOW -70C.   SUFFICIENT INSTABILITY WITH OVER
2000 J/KG MUCAPES AND VERY SATURATED LOWER PROFILES (RAP ANALYSIS
SUGGESTING 20C TDS AT 850MB) WILL SUPPORT HIGHLY EFFICIENT
RAINFALL PROCESSES THROUGH THESE DEEP UPDRAFTS WITH 2.5"/HR RATES
POSSIBLE.

GIVEN THE WAVE IS ALSO FAIRLY FLAT ACROSS N IND INTO UPSTREAM
CONFLUENCE...THERE IS DEEP NEARLY UNIDIRECTIONAL FLOW SUPPORTIVE
OF TRAINING/REPEAT TRACKS.  OVERALL THOUGH FORWARD PROGRESSION
SEEMS TO BE FAIRLY QUICK TO NOT ALLOW FOR EXTREME TOTALS WITH MUCH
OF THE HI-RES GUIDANCE SUGGESTING 2-3" SWATHS WITH ISOLATED 4"
TOTALS...AND UPSTREAM OBSERVED TOTALS BELOW 2".  HOWEVER GIVEN
SATURATED SOILS FROM MULTIPLE BOUTS OF HEAVY RAIN OVER THE LAST 7
DAYS (400-600% OF NORMAL PER AHPS)...GROUND CONDITIONS MAY BE NEAR
HYDROPHOBIC ALLOWING FOR GREATER RUN OFF AND FLASH FLOODING
CONCERNS.  FFG VALUES IN DELINEATED AREA OF CONCERN ARE GENERALLY
BELOW 2"/3HR OVER NW OH/SW MI/NE IL/NW IND AND BELOW 2.5" IN N
CENTRAL IND.  AS SUCH FLASH FLOODING IS CONSIDERED POSSIBLE. 

GALLINA

ATTN...WFO...CLE...DTX...GRR...ILN...IND...IWX...LOT...

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

LAT...LON   42478603 42098433 41898305 41558196 40638195
            40328304 40378391 40548508 40608638 40618776
            41378771 41808736 42208685 42398654