MESOSCALE PRECIPITATION DISCUSSION 0506
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EDT SUN JUL 22 2018

AREAS AFFECTED...NORTH-CENTRAL SD

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 220559Z - 220859Z

SUMMARY...THUNDERSTORMS ARE CONGEALING ACROSS NORTHERN SD.  HOURLY
RAIN TOTALS TO 2" WITH LOCAL AMOUNTS TO 4" ARE POSSIBLE.

DISCUSSION...AT THE UPPER LEVELS, A SHORTWAVE MOVING BY TO THE
NORTH ACROSS ND AND AN OUTFLOW JET FROM CONVECTION IN SOUTHWEST SD
ARE CONSPIRING WITH A GROWING INSTABILITY POOL IN SD WITH MU CAPE
VALUES OF 2000+ J/KG AND INFLOW AT 850 HPA OF 15-25 KTS TO HELP
CONGEAL CONVECTION OVER A SMALL AREA OF NORTHERN SD.  EFFECTIVE
BULK SHEAR OF 30-50 KTS IS HELPING TO ORGANIZE THE SMALL COMPLEX. 
PRECIPITABLE WATER VALUES ARE ESTIMATED TO BE 1.5-1.75" PER RAP
ANALYSES. 

THE MESOSCALE GUIDANCE IS NOT DOING WELL IN THIS AREA.  THE
EXPECTATION IS FOR THIS SMALL CLUSTER TO PERSIST FOR A SHORT
PERIOD OF TIME.  THE COMBINATION OF A COMPLEX IN SOUTHERN SD IS
FADING AND THE SHORTWAVE PASSING FARTHER EASTWARD ACROSS ND SHOULD
WEAKEN UPPER DIVERGENCE AND LEAD TO A COLLAPSE OF THE COMPLEX
WITHIN A FEW HOURS.  IF IT PERSISTS, VEERING LOW-LEVEL INFLOW
SHOULD INDUCE SOME SOUTHEASTERLY MOTION WITH TIME.  UNTIL IT DIES
OR MOVES, HOURLY RAIN TOTALS TO 2" WITH LOCAL AMOUNTS TO 4" ARE
POSSIBLE.

ROTH

ATTN...WFO...ABR...BIS...UNR...

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

LAT...LON   46080150 45810059 45240001 44810008 44570063
            44770138 45370226 45950243