MESOSCALE PRECIPITATION DISCUSSION 0349
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
912 PM EDT MON JUL 13 2015
 
AREAS AFFECTED...PORTIONS OF ERN ILLINOIS EWD ALONG THE OHIO RIVER
VALLEY 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 140111Z - 140700Z
 
SUMMARY...LOW FLASH FLOOD GUIDANCE WILL BE THE MAIN DRIVING FACTOR
IN AN INCREASED FLASH FLOOD THREAT EARLY TONIGHT ACROSS PORTIONS
OF THE OHIO VALLEY. ABUNDANT LOW LEVEL MOISTURE WILL SUPPORT
RAINFALL RATES BETWEEN 0.5 TO 1.5 IN/HR DESPITE EXPECTED FORWARD
PROPAGATION OF CONVECTION.

DISCUSSION...REGIONAL RADAR IMAGERY AS OF 0100Z SHOWED AN
EXPANDING COVERAGE OF THUNDERSTORMS ACROSS NRN ILLINOIS AND
INDIANA...LOCATED AHEAD OF AN EFFECTIVE COLD FRONT DROPPING
THROUGH SERN IOWA. DEWPOINTS IN THE WARM SECTOR ARE IN THE UPPER
70S TO LOW 80S...SUPPORTING EXTREME CAPE VALUES OF 5000 - 7000
J/KG...AS SEEN ON THE 00Z KILX SOUNDING. INSTABILITY FALLS OFF
RAPIDLY TO THE EAST ACROSS A WARM FRONT DRAPED SEWD ACROSS WRN
INDIANA. WHILE LOW LEVEL MOISTURE IS HIGH...THERE IS CERTAINLY
SOME DRY AIR ALOFT NOTED IN KILX AND KILN SOUNDINGS WHICH MAY HELP
TO ALLOW DRY AIR ENTRAINMENT AND POTENTIAL GROWTH INTO A SEWD
PROPAGATING CLUSTER OR TWO PER CORFIDI VECTOR WIND VECTORS.

AS ONGOING CONVECTION CONTINUES TO EXPAND OVER THE NEXT FEW HOURS
OVER ILLINOIS AND INDIANA...CONGLOMERATION INTO FORWARD
PROPAGATING CLUSTERS APPEARS LIKELY...WITH GENERAL MOVEMENT TOWARD
THE SOUTHEAST BETWEEN 20 AND 30 KTS THROUGH 07Z. RAINFALL RATES
ARE EXPECTED TO RANGE BETWEEN 0.5 AND 1.5 IN/HR...PERHAPS AS HIGH
AS 2 IN/HR WHERE LOCAL CELL MERGERS OCCUR. GIVEN ANTECEDENT
CONDITIONS ACROSS THE OHIO VALLEY...1 HR FLASH FLOOD GUIDANCE IS
QUITE LOW AS SHOWN IN THE MPD GRAPHIC. FOR THIS REASON...FLASH
FLOODING IS CONSIDERED POSSIBLE...DESPITE THE EXPECTED FORWARD
PROPAGATION OF CELLS.

OTTO

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

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

LAT...LON   41558752 41558691 41408612 41118507 40558377 
            40308339 39918290 39338282 38788329 38508404 
            38198450 38068553 38368673 39338762 40528827 
            41128824 41428799