MESOSCALE PRECIPITATION DISCUSSION 0285
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
728 PM EDT SUN JUN 10 2018

AREAS AFFECTED...PORTIONS OF THE MID-MISSISSIPPI & LOWER OH
VALLEYS

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

VALID 102327Z - 110527Z

SUMMARY...THUNDERSTORMS SLOWLY DROPPING THROUGH IL INTO
SOUTHERNMOST IN CONTINUE TO SHOW OCCASIONAL TRAINING
CHARACTERISTICS WHILE CELL COVERAGE SLOWLY EXPANDS.  HOURLY RAIN
TOTALS TO 2" WITH LOCAL AMOUNTS TO 4" ARE EXPECTED OVER THE NEXT
SEVERAL HOURS.

DISCUSSION...THUNDERSTORMS ARE ON THE VERGE OF LEAVING MPD #282
ACROSS IL AND SOUTHERN IN.  A MESOSCALE WAVE OF LOW PRESSURE SOUTH
OF SPRINGFIELD IL APPEARS TO BE HOLDING UP THE BOUNDARIES
PROGRESSION ACROSS IL WHILE THE REMAINDER OF THE OUTFLOW BOUNDARY
PLOWS FORWARD ACROSS THE OHIO RIVER NEAR THE IN/KY BORDER. 
DIVERGENCE ALOFT APPEARS TO BE SPONSORED BY A TRIO OF PAIR LEVEL
CIRCULATIONS OVER MO AND AN MCV MOVING ACROSS EASTERN IA. 
PRECIPITABLE WATER VALUES OF 1.5-1.75" LURK ACROSS THE AREA PER
GPS DATA.  INFLOW AT 850 HPA IS CONVERGENT OUT OF THE WEST AT
15-20 KTS PER VAD WIND PROFILES, NEAR OR JUST ABOVE THE MAGNITUDE
OF THE 850-400 HPA MEAN WIND.  THE LOW-LEVEL FLOW IS IMPORTING ML
CAPE VALUES OF ~2000 J/KG FROM EASTERN MO AND SOUTHERN IL. 
EFFECTIVE BULK SHEAR IS NEAR 25 KTS PER SPC MESOANALYSES.

THE 12Z WRF NSSL AND 18Z NAM CONEST APPEAR TO HAVE THE BEST IDEA
FOR EXPECTATIONS IN THIS REGION.  INFLOW INTO THE REGION IS NOT
EXPECTED TO FADE AND COULD BUMP UP SLIGHTLY LATER TONIGHT.  THIS
IS REFLECTED IN THE 12Z GFS-BASED GALVEZ-DAVISON INSTABILITY INDEX
WHICH SHOWS INCREASING INSTABILITY  AND THE THREAT OF GREATER CELL
COVERAGE WITH TIME.  CONVECTION SHOULD CONTINUE TO BACKBUILD INTO
NORTHEAST MO/POSSIBLY SOUTHEAST IA WITH TIME TOWARDS THE EASTERN
FRINGE OF A LARGER BUBBLE OF 2500-3000 J/KG INSTABILITY.  THE
CONCERN IS THAT WHEN CIN SETS IN AROUND 02Z THAT THE CONVECTION
COULD HALT ITS SOUTHWARD PROGRESSION ACROSS IL -- OR WORSE --
SHIFT A LITTLE NORTHWARD INTO THE MU CAPE GRADIENT WHICH IS BACK
UP ACROSS CENTRAL IL.  THE MESOSCALE GUIDANCE SHOWS A SIGNAL FOR
LOCAL AMOUNTS IN THE 3-4" RANGE, WHICH APPEARS REASONABLE.  HOURLY
RAIN TOTALS UP TO 2" CONTINUE TO BE EXPECTED.  THESE TOTALS SHOULD
CHALLENGE THREE HOURLY FLASH FLOOD GUIDANCE VALUES IN THE AREA.

ROTH

ATTN...WFO...DMX...DVN...EAX...ILX...IND...LSX...PAH...

ATTN...RFC...LMRFC...MBRFC...NCRFC...OHRFC...

LAT...LON   41069213 40318945 39048719 37898714 37798813
            38279051 39329247 40519310