MESOSCALE PRECIPITATION DISCUSSION 0470
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
952 AM EDT WED JUL 12 2017

AREAS AFFECTED...NE IOWA...ANY SE WISCONSIN...N ILLINOIS...SW
MICHIGAN...N INDIANA

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

VALID 121350Z - 121750Z

SUMMARY...MULTIPLE ROUNDS OF VERY HEAVY RAINFALL ARE EXPECTED TO
CONTINUE THROUGH THE LATE MORNING HOURS.  AREAS OF TRAINING
CONVECTION MAY LEAD TO ADDITIONAL FLOODING CONCERNS, ESPECIALLY
OVER AREAS THAT GOT SIGNIFICANT RAINFALL OVERNIGHT.  RAINFALL
RATES MAY EXCEED TWO INCHES PER HOUR AT TIMES WITH THE STRONGEST
CONVECTION.

DISCUSSION...THE MCS THAT PRODUCED WIDESPREAD HEAVY RAINFALL
ACROSS MINNESOTA AND WISCONSIN OVERNIGHT IS NOW STEADILY
PROGRESSING TOWARDS THE EAST-SOUTHEAST.  THE SOUTHERN PORTION OF
THIS MCS IS WHERE THE GREATEST CONCERN OF EXCESSIVE RAINFALL WILL
BE SINCE THE NORTHERN PORTION IS MORE PROGRESSIVE.  AN AGGRAVATING
FACTOR IN THE FLASH FLOODING POTENTIAL ARE THE GREATLY REDUCED
FLASH FLOOD GUIDANCE VALUES OVER PARTS OF SOUTHERN WISCONSIN AND
NORTHERN ILLINOIS WHERE SEVERAL INCHES OF RAIN FELL OVERNIGHT.  AN
ADDITIONAL AREA OF TRAINING CONVECTION IS EXPECTED OVER NORTHEAST
IOWA IN RESPONSE TO INCREASING WARM AIR ADVECTION NEAR THE FRONTAL
ZONE.

MOISTURE AND THERMODYNAMIC PARAMETERS CONTINUE TO BE FAVORABLE FOR
HEAVY RAINFALL FROM ANY STORMS THAT DEVELOP.  THE LATEST PW VALUES
FROM GPS DATA AND LOCAL RAOBS ARE IN THE 1.75 TO 2 INCH RANGE, AND
MUCAPES FROM THE SPC MESOANALYSIS ARE ON THE ORDER OF 1500 TO 2500
J/KG.  THE INSTABILITY IN THE WARM SECTOR SHOULD STEADILY INCREASE
OVER THE NEXT FEW HOURS AS PORTRAYED BY THE LATEST RAP MODEL
GUIDANCE, EXCEEDING 3000 J/KG IN PLACES BY 16Z.

THE LATEST HI-RES GUIDANCE APPEARS TO BE STRUGGLING WITH THE
MAGNITUDE OF THE PRECIPITATION OVER THIS REGION, AND MOST ARE
DISPLACED TOO FAR NORTH WITH THE MAIN QPF AXIS ACCORDING TO THE
RECENT RADAR TRENDS. EXPECT PATCHY AREAS OF 1 TO 3 INCHES OF
RAINFALL THROUGH 18Z, WITH ISOLATED HIGHER AMOUNTS POSSIBLE.

HAMRICK

ATTN...WFO...ARX...DMX...DVN...GRR...IWX...LOT...MKX...MPX...

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

LAT...LON   43699266 43669125 43478952 43318832 43208721
            42968571 42508502 41778484 41178499 41098572
            41148688 41238811 41428937 41639057 41889175
            42169269 42829405 43489388