MESOSCALE PRECIPITATION DISCUSSION 0134...CORRECTION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 AM EDT WED JUN 26 2013
 
AREAS AFFECTED...EASTERN IA...FAR SOUTHEAST MN...SOUTHWEST
WI...NORTHERN AND CENTRAL IL 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 260555Z - 260930Z
 
SUMMARY...A GROWING AREA OF CONVECTION IS DEVELOPING ACROSS
EASTERN IA.  DUE TO THE RECENT RAINFALL OVER THE PAST SEVERAL
DAYS, FLASH FLOODING IS LIKELY NEAR AND DOWNSTREAM OF EASTERN IA.

DISCUSSION...SOUTHWESTERLY LOW-LEVEL INFLOW OF ROUGHLY 35 KNOTS AT
850 HPA IS OVERRIDING A MESOSCALE SURFACE BOUNDARY ACROSS SOUTHERN
IA, LEADING TO A NEW BATCH OF THUNDERSTORM ACTIVITY, WHICH SHOULD
CONTINUE TO ORGANIZE.  THE REGION IS JUST AHEAD OF A
NEGATIVELY-TILTED SHORTWAVE ALOFT, WHICH IS PROMOTING EXCELLENT
OUTFLOW OVER THE REGION.  SATELLITE- DERIVED CAPE VALUES ARE IN
THE 2500-4500 J/KG RANGE ACROSS IA, ADVERTISING SIGNIFICANT
INSTABILITY.  PRECIPITABLE WATER VALUES ARE IN THE 1.75-2 INCH
RANGE, WHICH IS WELL ABOVE NORMAL FOR JUNE.

WHILE THE THUNDERSTORMS ARE INITIALLY ELEVATED IN NATURE, BELIEVE
AS THE CONVECTIVE COMPLEX BECOMES BETTER ORGANIZED THAT THE SYSTEM
WILL BEGIN TO MOVE ON AN EAST-SOUTHEAST TO SOUTHEAST TRAJECTORY AS
A LOW-LEVEL COLD POOL DEVELOPS IN ASSOCIATION WITH THE CLUSTER,
WITH CONVECTION MOVING CLOSER TO THE MESOSCALE STATIONARY
BOUNDARY.  THERE COULD BE BACKBUILDING ACROSS THE REGION OVER THE
NEXT FEW HOURS -- NOTED WITHIN RECENT GFS-BASED CORFIDI VECTORS --
AS THE LOW-LEVEL JET INCREASES, WHICH INCREASES THE RISK OF FLASH
FLOODING NEAR AND DOWNWIND OF EASTERN IA.  THIS COULD
SIGNIFICANTLY LENGTHEN THE BAND WITH TIME.  FLASH FLOOD GUIDANCE
IS QUITE LOW ACROSS THE REGION DUE TO SEVERAL DAYS OF HEAVY
RAINFALL, ON THE ORDER OF 1-1.5 INCHES IN THREE HOURS.  A QUICK
2-4 INCHES OF RAINFALL ACROSS THE SATURATED REGION WILL LEAD TO
FLASH FLOODING OVER THE NEXT FEW HOURS.

ROTH

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

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

LAT...LON   40238808 39148957 40719147 42239341 43489313 43618993
            42018805 40238808