MESOSCALE PRECIPITATION DISCUSSION 0235
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
514 PM EDT WED MAY 30 2018

AREAS AFFECTED...NORTHEAST IL....SOUTHEAST WI

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

VALID 302115Z - 310115Z

SUMMARY...SLOW MOVING CONVECTION ALONG A NORTH SOUTH ORIENTED AXIS
IN A HIGH MOISTURE ENVIRONMENT COULD POSE A FLASH FLOOD THREAT
INTO THE EARLY EVENING HOURS. 

DISCUSSION...REGIONAL RADARS INDICATED A NORTH TO SOUTH ORIENTED
AXIS OF CONVECTION FORMING OVER NORTHEAST IL. THE CONVECTION WAS
FORMING IN AN AREA OF 1000-1500 J/KG MLCAPE STRETCHING FROM FAR
SOUTHEAST WI ACROSS MUCH OF CENTRAL AND EASTERN IL. THE AXIS OF
CONVECTION IS ON THE WEST SIDE OF THE CIRCULATION OF ALBERTO...AND
PRECIPITABLE WATER VALUES ON THE WESTERN PERIPHERY OF THE
CIRCULATION WERE NEAR 2.00 INCHES (WHIC HIS BETWEEN TWO AND THREE
STANDARD DEVIATIONS ABOVE THE MEAN).

THE KLOT RADAR HAS SHOWN HOURLY RAINFALL RATES BETWEEN 1.50 AND
2.00 INCHES WITH CELLS OVER WEST OF CHICAGO. RAP SOUNDINGS SHOWED
SOME DRY AIR IN THE MID LEVELS...AND THIS COULD BE CONTAMINATING
RAINFALL RATES AS A RESULT. AS A NEGATIVELY TILTED LONG WAVE
TROUGH APPROACHES WI LATE THIS AFTERNOON...AND THE CIRCULATION
ASSOCIATED WITH ALBERTO PASSES TO THE EAST...THE AXIS IS EXPECTED
TO MOVE SLOWLY EASTWARD THROUGH 31/00Z.

THERE IS AN INCREASING HIGH RESOLUTION MODEL SIGNAL FOR HEAVY
RAINFALL OVER THE REGION. BOTH THE MOST RECENT HRRR AND
EXPERIMENTAL HRRR SHOWING LOCAL 3.00+ INCH RAINFALL AMOUNTS OVER
NORTHEAST IL...AND THE EXPERIMENTAL HRRR INDICATED THE POTENTIAL
FOR 6.00+ INCHES BETWEEN KRFD AND KORD. WHILE THESE VALUES MAY BE
ON THE HIGH SIDE...SLOW MOVING CELLS IN A HIGH MOISTURE
ENVIRONMENT POSE A FLASH FLOOD THREAT INTO THE EARLY EVENING.

HAYES

ATTN...WFO...ILX...LOT...MKX...

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

LAT...LON   43838868 43538779 41308750 40208768 40148838
            41128902 42658896