MESOSCALE PRECIPITATION DISCUSSION 0418
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
141 PM EDT FRI JUN 30 2017

AREAS AFFECTED...EAST CENTRAL IL...NORTHERN IND...NORTHWEST OH

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

VALID 301741Z - 302241Z

SUMMARY...FAVORABLY ORIENTED LINE OF CONVECTION SUPPORTIVE OF
TRAINING LEADING TO POTENTIAL FLASH FLOODING.

DISCUSSION...EXPERIMENTAL GOES-16 WV/VISIBLE IMAGERY DENOTES
STRONG/COMPACT MCV IN N MO WITH EXCELLENT ANTICYCLONIC OUTFLOW
CHANNEL DIRECTED NORTH/NNEWARD INTO THE MEAN 80KT POLAR JET STREAK
ACROSS WI/N MI.  FAIRLY CLEAR SKIES DUE TO THIS ORIENTATION HAS
LEAD TO IMPRESSIVE INSTABILITY TO BUILD ACROSS IL/IN WITH
ACCESSIBLE 2000+ J/KG MLCAPES.  SOUTHERLY SFC TO VEERING SWLY
850MB FLOW SUPPORTS SUFFICIENT CONVERGENCE TO SPARK CONVECTION
ACROSS THIS WARM SECTOR.  OF GREATER CONCERN ALONG MID-LEVEL
CONVERGENCE BAND BETWEEN MCV AND EXITING SHORTWAVE OVER NY IS
ORIENTED FAVORABLY TO THE MEAN WIND WITH THE SOLID CONVERGENCE. 
DUE TO UPSTREAM SHORTWAVE/INFLOW FLUX PROPAGATION VECTORS ARE VERY
WEAK 0-5KTS DUE EAST PER THE RAP SUGGESTIVE OF SOME WEAK
BACKBUILDING ALONG THE LINE OF CONVECTION TO SUPPORT EXTENDED
DURATION OF HEAVY RAIN.  ADDITIONAL DOWNSTREAM SCATTERED CELLS ARE
LIKELY TO CONSOLIDATE AS WELL POTENTIALLY LEADING TO A FOCUSING
BOUNDARY AS WELL FURTHER SUPPORTING THE TRAINING POTENTIAL THROUGH
THE AFTERNOON.  

ILX 12Z SOUNDING AND TPW ANALYSIS SUGGESTS SOME DRY AIR TO REDUCE
VERY HIGH PRECIPITATION RATES AS WELL AS SOME COLD POOLING BUT
WITH TPWS OF 1.75" AND MODEST FAIRLY UNOBSTRUCTED LOW LEVEL
MOISTURE FLUX MAY SUPPORT RATES UP TO 2"/HR.  ALONG WITH THE
TRAINING THE POTENTIAL FOR MULTIPLE LINES OF 2-4" PARTICULARLY IN
A LINE FROM E CENTRAL IL TO NW OH.  THIS EVOLUTION IS GENERALLY
SUPPORTED BY HI-RES CAM GUIDANCE THOUGH EACH MODEL PRECISE
LOCATION OF INITIATION ARE OFFSET ENOUGH TO NOT HAVE FULL
CONFIDENCE IN PRECISE MODEL RUN/OUTPUT FOR SUGGESTION THOUGH
HRRRV3 SEEMS A BIT MORE PREFERABLE BASED ON CURRENT TRENDS.

GALLINA

ATTN...WFO...ILN...ILX...IND...IWX...LOT...

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

LAT...LON   41678510 41518411 40348407 39538580 39098691
            38848772 39208875 39888889 41228732 41568627