MESOSCALE PRECIPITATION DISCUSSION 0686
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
500 AM EDT THU SEP 22 2016
 
AREAS AFFECTED...SOUTH-CENTRAL MN & NORTHERN IA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 220900Z - 221305Z
 
SUMMARY...THUNDERSTORMS CONTINUE TO BACKBUILD AND DROP SOUTH
FARTHER INTO IA.  HOURLY RAIN RATES UP TO 2.5" AND LOCAL AMOUNTS
IN THE 3-5" COULD LEAD TO FLASH FLOODING.

DISCUSSION...THUNDERSTORMS ARE SLOWLY SAGGING SOUTH AS OUTFLOW
BOUNDARIES FROM CONVECTION NEAR THE MN/IA BORDER PUSH THE MAIN
SURFACE BOUNDARY SOUTH.  HOURLY RAIN RATES CONTINUE TO
OCCASIONALLY BREACH 2.5" ON RADAR IMAGERY. SATELLITE IMAGERY SHOWS
THE MAIN CLUSTER ALONG THE MN/IA BORDER SHOWING COOLING CLOUD TOPS
AS OF LATE.  AN INVADING BATCH OF SCATTERED THUNDERSTORMS AND
THEIR OUTFLOW BOUNDARY ARE APPROACHING THE AREA FROM THE WEST AT
~25 KTS AHEAD OF A SHORTWAVE MOVING ACROSS CENTRAL NE. 
PRECIPITABLE WATER VALUES OF 1.6-1.8" LIE ACROSS THE AREA PER GPS
DATA.  INFLOW AT 850 HPA OF 30-45 KTS IS IMPORTING MUCAPES OF
1000-2000 J/KG INTO THE BOUNDARY.

WITH LOW LEVEL INFLOW SLOWLY DECREASING ALONG WITH AVAILABLE
INSTABILITY, THE CLOCK IS TICKING ON ORGANIZED CONVECTION IN THIS
REGION. THE 00Z SSEO NEIGHBORHOOD PROBABILITIES ADVERTISE 13Z AS
THE ENDING TIME, WHICH SEEMS REASONABLE CONSIDERING THE
INSTABILITY REMAINING.  MESOSCALE GUIDANCE ADVERTISES LOCAL
AMOUNTS IN THE 3-5" RANGE.  HOURLY RAIN RATES UP TO 2.5" ARE
POSSIBLE IN BACKBUILDING CONVECTION, CELL TRAINING, AND POSSIBLE
CELL MERGERS BETWEEN THE NE ACTIVITY AND IA ACTIVITY IN THE NEXT
SEVERAL HOURS.  FLASH FLOODING IS CONSIDERED POSSIBLE,
PARTICULARLY IN AREAS WITH PARTIALLY SATURATED SOILS.  

ROTH

ATTN...WFO...ARX...DMX...DVN...FSD...MPX...

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

LAT...LON   44469392 43339169 42719155 42069232 41899377 
            41909471 42109542 42339585 42889621 43609595 
            44289526