MESOSCALE PRECIPITATION DISCUSSION 0501
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
522 PM EDT FRI SEP 18 2015
 
AREAS AFFECTED...EASTERN IA...NORTHERN IL...SOUTHERN WI 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 182121Z - 190321Z
 
SUMMARY...ADDITIONAL RAINFALL AMOUNTS OF 2-3 INCHES MAY CAUSE
FLASH FLOODING.

DISCUSSION...A SURFACE WAVE CURRENTLY CENTERED OVER NORTHWESTERN
MO IS EXPECTED TO TRACK NORTHEAST ALONG A SLOW-MOVING BOUNDARY
EXTENDING FROM THE UPPER GREAT LAKES BACK INTO THE LOWER MO
VALLEY.  LATEST MESOANALYSIS SHOWS A POOL OF 1.75-2 INCH PWS
CENTERED FROM NORTHEASTERN MO/SOUTHEASTERN IA TO CENTRAL IL.  THIS
MOISTURE IS FORECAST TO SURGE NORTH ALONG AN AXIS OF AMPLIFYING
LOW LEVEL FLOW AHEAD OF THE WAVE.  RECENT HI-RES
GUIDANCE...INCLUDING THE 19/20Z HRRR..12Z HRW-ARW/NMMB AND THE
NSSL-WRF GENERALLY SHOW WIDESPREAD ADDITIONAL 0.5-INCH RAINFALL
AMOUNTS...WITH LOCALLY HEAVY AMOUNTS OF 2-3 INCHES THROUGH 03Z. 
THE GENERAL CONSENSUS OF THESE MODELS IS THAT THE HEAVIEST AMOUNTS
WILL FOCUS FROM EAST-CENTRAL IA NORTHEASTWARD ACROSS NORTHWESTERN
IL INTO SOUTHERN WI...WHERE STRONG LOW LEVEL CONVERGENCE ALONG THE
FRONTAL BOUNDARY AND UPPER JET FORCING IS EXPECTED TO AFFORD THE
STRONGEST LIFT.  HOWEVER...THE BETTER MOISTURE/INSTABILITY IS
EXPECTED TO CENTER FURTHER TO THE SOUTHEAST...THE NSSL-WRF AND THE
HRW-ARW INDICATE A SECOND AXIS OF HEAVY AMOUNTS FALLING ACROSS
CENTRAL IL.  THESE HEAVY AMOUNTS MAY CAUSE FLASH FLOODING.  FLASH
FLOODING IS ESPECIALLY A CONCERN ACROSS AREAS THAT HAVE ALREADY
BEEN IMPACTED BY HEAVY RAINS OVER THE PAST DAY...PARTICULARLY
PORTIONS OF SOUTHERN WI AND NORTHERN IL.

PEREIRA

ATTN...WFO...ARX...DMX...DVN...ILX...LOT...LSX...MKX...

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

LAT...LON   43508857 43228797 42638782 42158777 41008789 
            40138896 39459108 40809046 41139109 41159234 
            41589251 42179152 42639060 43308939