MESOSCALE PRECIPITATION DISCUSSION 0344
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
534 PM EDT SAT JUL 11 2015
 
AREAS AFFECTED...NERN MISSOURI...SERN IOWA INTO CNTRL ILLINOIS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 112133Z - 120330Z
 
SUMMARY...CONVECTION IS EXPECTED TO INCREASE NEAR A WARM FRONT AND
OUTFLOW BOUNDARY FROM THE ERN IOWA/MISSOURI BORDER INTO CNTRL
ILLINOIS OVER THE NEXT FEW HOURS...LEADING TO A THREAT FOR FLASH
FLOODING AS CELLS TRAIN TOWARD THE EAST. 6 HOUR RAINFALL AMOUNTS
MAY REACH 3-5 INCHES IN A FEW SPOTS.

DISCUSSION...LATEST RADAR SHOWED CONVECTION DEVELOPING ALONG A
WARM FRONT EXTENDING SEWD ACROSS SERN IOWA AND INTO
ILLINOIS...JUST EAST OF THE MISSISSIPPI RIVER. AN OUTFLOW BOUNDARY
FROM THIS MORNINGS RAINFALL WAS ALSO SEEN ON VISIBLE IMAGERY AND
IN SURFACE OBSERVATIONS IN NRN MISSOURI...INTERSECTING THE WARM
FRONT NEAR PPQ. 

TRENDS IN RADAR SHOW INCREASING CONVECTION FROM LEE COUNTY IOWA
INTO PORTIONS OF CNTRL ILLINOIS...IN THE WAKE OF A WELL DEFINED
SHORTWAVE OVER THE WISCONSIN/ILLINOIS BORDER. RECENT PRECIPITABLE
WATER VALUES FROM GPS SITES SHOW 1.6 TO 1.8 INCHES OVER THE
REGION...WHICH WHEN COMBINED WITH AMPLE INSTABILITY SOUTH OF THE
WARM FRONT...APPEARS CAPABLE OF HEAVY RAINFALL RATES...AS OBSERVED
BY IOWA MESONET SITE IN MORGAN COUNTY WITH 2.1 INCHES IN 20
MINUTES AT 2015Z. 

WATER VAPOR SATELLITE IMAGERY SHOWED DIFFLUENT FLOW ACROSS THE
REGION BUT SOME DRY AIR ALOFT MOVING IN OVER THE THREAT AREA WHICH
MAY REDUCE RAINFALL EFFICIENCY SOME WITH DRY AIR ENTRAINMENT.
STILL...RAP MODEL GUIDANCE SHOWS 850 MB MOIST INFLOW FROM THE WSW
AT 20-30 KTS CONTINUING THROUGH 03Z...AND STORM MOTIONS GENERALLY
OFF TOWARD THE EAST. OVERRUNNING OF THE WARM FRONT AND ERN POTIONS
OF THE OUT FLOW SHOULD SUPPORT REGENERATION OF CONVECTION OVER THE
NEXT FEW HOURS. THIS SETUP WILL ALLOW PERIODS OF TRAINING FROM THE
ERN IOWA/MISSOURI BORDER INTO CNTRL ILLINOIS. RECENT HI-RES MODEL
GUIDANCE SUPPORTS THE GENERAL IDEA OF HEAVY RAINFALL...WITH THE
12Z ARW AND SEVERAL RUNS OF THE HRRR SUPPORTING PLACEMENT MOST
FAVORABLY.

OTTO

ATTN...WFO...DMX...DVN...EAX...ILX...LOT...LSX...

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

LAT...LON   41399263 41269080 41148851 40678760 39388777 
            38958867 39249093 39819283 40209323 41009331