MESOSCALE PRECIPITATION DISCUSSION 0375
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
541 PM EDT WED JUN 22 2016
 
AREAS AFFECTED...PORTIONS OF NORTHERN IL AND IN 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 222141Z - 230341Z
 
SUMMARY...THUNDERSTORMS ARE EXPECTED TO EXPAND IN COVERAGE AND
INTENSITY ACROSS NORTHERN IL AND CENTRAL IN OVER THE NEXT SEVERAL
HOURS.  HOURLY RAIN RATES UP TO 2.5" COULD LEAD TO FLASH FLOODING.

DISCUSSION...SEVERAL THUNDERSTORMS LIE ACROSS NORTHERN IL AND
NORTHWEST IN, ELEVATED OVER A PAIR OF SURFACE BOUNDARIES WITHIN
THE BACK EDGE OF AN INSTABILITY GRADIENT IN THE AREA OF MAXIMUM
MOISTURE CONTENT.  CIN NEAR THE BOUNDARY IS UNLIKELY TO ERODE THIS
AFTERNOON/EVENING AS 700 HPA TEMPERATURES ARE >= 12C IMPLYING THE
PRESENCE OF A CAPPING INVERSION IN THE MIDWEST, SEEN NICELY ON THE
SPECIAL 18Z ILX AND DVN SOUNDINGS.  INFLOW AT 850 HPA IS 30-40 KTS
PER AREA VAD WIND PROFILES.  MUCAPES OF 2000-4500 J/KG LIE
UPSTREAM IN SOUTHERN IA, CENTRAL IL, AND WESTERN KY PER RECENT SPC
MESOANALYSES.  PRECIPITABLE WATER VALUES ARE 1.8"-1.9" PER RECENT
GPS VALUES.

THE BREADTH OF INFLOW AT 850 HPA IS EXPECTED TO INCREASE MARKEDLY
OVER THE NEXT SEVERAL HOURS AS A SQUEEZE PLAY ENSUES ALOFT BETWEEN
AN UPPER LOW MOVING ACROSS NORTHWEST MN AND BROAD RIDGING ACROSS
THE SOUTHERN PLAINS/LOWER TO MID MISSISSIPPI VALLEY.  SOME EROSION
TO THE CAPPING INVERSION IS FORECAST IN IL, WHICH COULD ALLOW FOR
SOME SOUTHWARD SHIFT WITH TIME, SIMILAR TO LAST NIGHT'S IA
CONVECTIVE COMPLEX.  

THE CAM/MESOSCALE GUIDANCE SHOWS ITS USUAL DISPERSION LOCATION AND
AMOUNT-WISE, WITH MOST OF THE GUIDANCE SHOWING A SIGNAL FOR LOCAL
2-4" AMOUNTS THROUGH 04Z ACROSS PORTIONS OF NORTHERN IL AND IN. 
SOME GUIDANCE -- SUCH AS THE 18Z NAM CONEST, 12Z SPCWRF, AND 18Z
HRRR EXPERIMENTAL RUNS -- SHOWS A SLIGHT SEPARATION BETWEEN TWO
MAXIMA IN IL AND IN.  GALVEZ-DAVISON INDEX VALUES EXCEED 50 BY 03Z
IN CENTRAL IN -- AN INDICATION FOR WIDESPREAD THUNDERSTORMS.  THE
SEPARATION COULD BE DUE TO A SLIGHT MINIMUM IN THE INSTABILITY
FIELD ACROSS CENTRAL IL, WHERE MUCAPES ARE A MERE 2000-2500 J/KG
THOUGH SUNNY SKIES IN THE AREA COULD EVEN OUT THIS DISCREPANCY
PRIOR TO SUNSET.  HEAVY RAINS COULD PILE UP QUICKLY, AS HOURLY
PRECIPITATION RATES COULD REACH 2.5" DUE TO CELL TRAINING. 
ORGANIZED STORMS SHOULD MOVE EAST-SOUTHEAST AT UP TO 35-40 KTS, A
COMPROMISE OF THE FORWARD PROPAGATING CONVECTIVE VECTORS AND THE
1000-500 HPA THICKNESS PATTERN.  FLASH FLOODING IS POSSIBLE IN AN
AREA WITH SATURATING SOILS.

ROTH

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

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

LAT...LON   42538921 42478758 41998658 41328578 39768481 
            39648635 40248793 42109027 42509039