MESOSCALE PRECIPITATION DISCUSSION 0267
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
808 PM EDT WED JUN 24 2015
 
AREAS AFFECTED......CENTRAL AND SOUTHERN IA... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 250000Z - 250500Z
 
SUMMARY...CONVECTION DEVELOPING NORTH OF A SURFACE WARM FRONT
ACROSS IA IS EXPECTED TO GROW UPSCALE INTO AN MCS. THE RESULTING
MCS SHOULD PRODUCE FLASH FLOODING OVER AREAS THAT RECEIVED HEAVY
RAIN EARLIER. 

DISCUSSION...CONVECTION IS BEGINNING TO DEVELOP ACROSS WEST
CENTRAL IA NORTH OF A SURFACE WARM FRONT. THE CONVECTION APPEARS
TO BE FORMING IN AN AREA OF 850 MB FRONTOGENESIS...NEAR A 1.90
INCH PRECIPITABLE WATER AXIS. AS A 20 TO 30 KNOT LOW LEVEL
SOUTHWEST FLOW TRANSPORTS 3500 TO 4500 J/KG AIR UP AND OVER THE
FRONT... CONVECTION IS EXPECTED TO DEVELOP RAPIDLY ACROSS CENTRAL
AND SOUTHERN IA. 

THE INITIAL CONVECTIVE MODE IS EXPECTED TO FEATURE SEVERE
WEATHER...MAINLY IN THE FORM OF WIND AND HAIL...WITH MID LEVEL DRY
AIR IN PLACE. HOWEVER...THE LATEST RAP SOUNDINGS SHOWED THE COLUMN
MOISTENING WITH TIME...AS WARM RAIN PROCESSES DOMINATE THE
CONVECTIVE MODE TOWARD 04Z. AS THE CONVECTION FOLLOWS THE LOW
LEVEL MOIST TONGUE (WITH PRECIPITABLE WATER VALUES TOPPING 2
INCHES ACROSS MUCH OF CENTRAL AND SOUTHERN IA)...FLASH FLOODING
BECOMES MORE OF A CONCERN.

THE LATEST HRRR RUN PLACES THE HEAVIEST RAINFALL (LOCALLY BETWEEN
2 AND 4 INCHES) ACROSS CENTRAL AND SOUTHERN IA...POSSIBLY REACHING
NORTHEAST MO AFTER 04Z. THE REMAINDER OF THE HIGH RESOLUTION
GUIDANCE PLACES THE HIGHEST RAINFALL AMOUNTS FURTHER NORTH. BASED
ON THE PLACEMENT OF THE INITIAL CONVECTION...IT APPEARS AS THOUGH
THE LATEST HRRR MAY HAVE THE BEST HANDLE ON WHERE THE HEAVIEST
RAINFALL WILL OCCUR.

THREE HOUR FLASH FLOOD GUIDANCE HAS DROPPED TO 1.50 INCHES OR
BELOW ACROSS MUCH OF IA...DUE TO THE HEAVY RAIN THAT FELL EARLIER.
THE COMBINATION OF HIGH RAINFALL RATES AND LOWER FLASH FLOOD
GUIDANCE MAKES FLASH FLOODING LIKELY LATER THIS EVENING.

HAYES 

ATTN...WFO...DMX...DVN...EAX...FSD...OAX...

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

LAT...LON   42529428 42359272 41609144 41119101 40909104 
            40769116 40519158 40479207 40559281 40689331 
            40859400 41369573 41779608 42389588 42419570 
            42449565