MESOSCALE PRECIPITATION DISCUSSION 0230
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
717 PM EDT MON MAY 23 2016
 
AREAS AFFECTED...EASTERN NEBRASKA...WESTERN IA...EXTREME SOUTHWEST
MN...EXTREME SOUTHEAST SOUTH DAKOTA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 232316Z - 240300Z
 
SUMMARY...THE THREAT OF FLASH FLOODING EXISTS FROM PARTS OF
EASTERN NEBRASKA IN TO WESTERN IA AS THE APPROACH OF A SHORTWAVE
SUPPORTS CONVECTION IN A REGION OF PERSISTENT MOISTURE FLUX.
TRAINING OF CELLS IS A CONCERN AS THE AXIS OF CONVECTION BECOMES
ALIGNED PARALLEL WITH THE LOW LEVEL FLOW. 


DISCUSSION...LATE AFTERNOON/EARLY EVENING RADAR SHOWED THAT HEAVY
RAINFALL PRODUCING CELLS WERE BECOMING MORE NUMEROUS OVER EASTERN
NEBRASKA...WITH BETTER ORGANIZED NOW THAT CONVECTION TO ITS SOUTH
HAS WEAKENED.  LAYERED PRECIPITABLE WATER SATELLITE IMAGERY SHOWED
THE AXIS OF HIGHEST PRECIPITABLE WATER VALUES OVER THIS AREA...AND
CELLS HAVE BEEN ABLE TO PRODUCE LOCALLY HEAVY RAINFALL IN A SHORT
TIME AS SHOWN BY MORE THAN 1.5 INCHES OF RAIN IN LESS THAN AN HOUR
OVER EXTREME NORTHWEST IA ACCORDING TO THE KFSD 88D. 

THE HIGH RESOLUTION/RAPIDLY REFRESHING MODELS...ESPECIALLY THE
HRRR AND THE HRRR TIME LAGGED ENSEMBLE...HAVE POINTED TOWARDS THIS
AREA FOR SEVERAL RUNS NOW ALTHOUGH THEIR FOCUS APPEARS TO HAVE
BEEN A BIT TOO FAR EAST.  THE ARW HAS NOT BEEN DOING PARTICULARLY
WELL IN THIS AREA SO FAR WITH RESPECT TO RAFL AMOUNTS. 

GIVEN THE APPROACH OF A SHORTWAVE FROM THE SOUTHWEST...THINK THE
THREAT OF POTENTIALLY HEAVY RAINFALL WILL CONTINUE UNTIL AROUND
03Z.  

THE FLASH FLOOD GUIDANCE NUMBERS ARE LOWEST UP IN NORTHWEST
IA...ON THE ORDER OF 1.5 INCHES PER 3 HOURS...AND INCREASE TO
LOCALLY MORE THAN 2.5 INCHES PER 3 HOURS ACROSS THE SOUTH END OF
THE OUTLOOK AREA.  THIS WOULD IMPLY THE BETTER CHANCES FOR
EXCESSIVE MAY BE ON THE NORTH END OF THE AREA BUT POTENTIAL FOR
SOME TRAINING OF HEAVY RAINFALL PRODUCING CELLS EXISTS ACROSS THE
SOUTH END AS WELL.

BANN

ATTN...WFO...DMX...FSD...GID...MPX...OAX...

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

LAT...LON   43909551 43749419 42159553 41239603 40579670 
            40599760 41319786 41989740 42949661