MESOSCALE PRECIPITATION DISCUSSION 0360
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
224 PM EDT SAT JUL 18 2015
 
AREAS AFFECTED...AREAS AROUND SOUTHERN LAKE MICHIGAN 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 181823Z - 182223Z
 
SUMMARY...INCREASING INSTABILITY AND SUFFICIENT MOISTURE AND
INFLOW COULD LEAD TO FLASH FLOODING OVER SATURATED SOILS.

DISCUSSION...A WAVE ALONG AN OUTFLOW BOUNDARY SET DOWN BY A
DEPARTING SQUALL LINE HAS BEGUN TO INITIATE SCATTERED
THUNDERSTORMS OVER SOUTHWEST WI, WHICH ARE MOVING ROUGHLY EASTWARD
AT 25-30 KTS.  MLCAPES OF 2000-4000 J/KG LURK ACROSS NORTHERN IL,
WHILE PRECIPITABLE WATER VALUES OF ~1.75" INHABIT THE REGION, AND
~30 KTS OF 850 HPA INFLOW INTERCEPTS THE BOUNDARY.

AS STORMS ORGANIZE, THEY SHOULD TURN EAST-SOUTHEAST AT 20-25 KTS
PER FORWARD PROPAGATING CONVECTIVE VECTORS.  CELL TRAINING IS
CONSIDERED THE MAIN FLASH FLOOD THREAT.  THE MESOSCALE GUIDANCE
HAS DONE POORLY IN THIS REGION SINCE YESTERDAY.  THE BEST FIT TO
THE AVAILABLE MOISTURE, INFLOW, AND INSTABILITY APPEAR TO BE THE
00Z ARW AND 16Z EXPERIMENTAL HRRR, WHICH ADVERTISE LOCAL AMOUNTS
IN THE 2-3" RANGE.  THE AVAILABLE MOISTURE SUPPORTS HOURLY RAIN
RATES UP TO 2", WHICH COULD FALL QUICKLY.  SINCE SOILS WERE
RECENTLY SATURATED BY THUNDERSTORMS YESTERDAY AFTERNOON, THIS
DEGREE OF RAINFALL COULD LEAD TO FLASH FLOODING.

ROTH

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

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

LAT...LON   43278815 42448628 41228633 41028769 41418934 
            41949017 42869045