MESOSCALE PRECIPITATION DISCUSSION 0359
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
747 PM EDT FRI JUN 17 2016
 
AREAS AFFECTED...SOUTHEAST SD...SOUTHWEST MN...FAR NORTHEAST
NEB...NORTHWEST CORNER OF IA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 172346Z - 180400Z
 
SUMMARY...STORMS OVER SOUTHWEST MN EARLY THIS EVENING HAVE BEEN
PRODUCING SOME INTENSE RAINFALL.  THIS CAN POSE A FLASH FLOOD RISK
THROUGH THE EVENING FROM SOUTHWEST MN INTO SOUTHEAST SD AS THE
STORMS MAKE THEIR WAY SOUTH.

DISCUSSION...THUNDERSTORMS FORMED OVER SOUTHWEST MN THIS AFTERNOON
ON THE TAIL END OF CONVECTION WHICH MOVED ACROSS THE NORTHERN PART
OF THE STATE EARLIER IN THE DAY.  RADAR ESTIMATES OF MORE THAN 3
INCHES PER HOUR HAVE BEEN NOTED UNDERNEATH THE MOST ACTIVE
CONVECTION AND WHERE CONVECTION WAS ABLE TO TRAIN.

PRECIPITABLE WATER VALUES ARE FAIRLY MODEST ACROSS THE REGION AT
1.5 TO 1.75 INCHES...AND H85 FLOW WAS PRETTY LIGHT.  BUT THE
STORMS HAVE FORMED RIGHT ALONG THE AXIS OF HIGHEST PWS AND THEY
HAVE BEEN ABLE TO TAP VERY HIGH SURFACE DEW POINTS AS SHOWN BY
MESONET STATIONS.  THIS...COMBINED WITH FAIRLY STEEP LAPSE RATES
AHEAD OF A FRONT APPROACHING FROM THE WEST...SHOULD KEEP
CONVECTION ACTIVE THROUGH MUCH OF THE EVENING. 

THE HRRR SEEMS TO HAVE HAD THE BEST HANDLE ON THE EARLY STAGES OF
THE STORMS EVOLUTION. SEVERAL RUNS OF THE HRRR-TIME LAGGED
ENSEMBLE POINTED TO THE AREA FROM MN BACK INTO SOUTHEAST SD/FAR
NORTHEAST NEB/NORTHWEST CORNER OF IA AS HAVING ABOUT 20 PERCENT
PROBABILITY OF RECEIVING 2 INCHES OF RAIN IN 3 HOURS THROUGH 04Z.
THE ARW ALSO POINTED TO THE POTENTIAL FOR HEAVY RAINFALL HERE BUT
ITS PLACEMENT MAY HAVE BEEN A BIT TOO FAR TO THE EAST.  

LOWEST VALUES OF 3-HOUR FLASH FLOOD GUIDANCE WERE ON THE ORDER OF
1.5 INCHES OVER THE SOUTHWEST CORNER OF MN...WITH AMOUNTS
GENERALLY ABOVE 2 INCHES ELSEWHERE.  THIS SUGGESTS THAT FLASH
FLOODING WILL BE POSSIBLE...ESPECIALLY IN REGIONS WHICH RECEIVE
MULTIPLE ROUNDS OF CONVECTION.

BANN

ATTN...WFO...FSD...MPX...OAX...

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

LAT...LON   44399706 44149549 44309442 43469541 42989590 
            42149694 42759781 43549792