MESOSCALE DISCUSSION 1634
   NWS STORM PREDICTION CENTER NORMAN OK
   0401 PM CDT SUN SEP 04 2016

   AREAS AFFECTED...CENTRAL SD

   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

   VALID 042101Z - 042230Z

   PROBABILITY OF WATCH ISSUANCE...80 PERCENT

   SUMMARY...A NEW SEVERE-WEATHER WATCH WILL LIKELY BE NEEDED TO THE
   EAST/NORTHEAST OF WW 465 ACROSS MAINLY CENTRAL SD THROUGH THIS
   EVENING.  IF CURRENT TRENDS OF INCREASING STORMS/INTENSITY PERSIST
   ACROSS THE NORTH AND NORTHEAST PORTIONS OF WW 465...THEN THIS WATCH
   ISSUANCE WILL NEED TO OCCUR SOONER THAN PREVIOUSLY EXPECTED.

   DISCUSSION...TRENDS IN MOSAIC RADAR IMAGERY...SINCE 20Z...SHOWED AN
   INCREASE IN STORM DEVELOPMENT/INTENSITY...WHILE IR SATELLITE IMAGERY
   INDICATED RAPIDLY COOLING CLOUD TOPS WITH THESE STORMS IN OGLALA
   LAKOTA TO JACKSON COUNTIES SOUTH DAKOTA.  THESE STORMS WERE LOCATED
   IN VICINITY OF A SURFACE BOUNDARY EXTENDING SOUTHWESTWARD FROM AN
   AREA OF LOW PRESSURE IN CENTRAL SD /NEAR PIR/...WITH THIS SAME
   BOUNDARY EXTENDING TO THE NORTHEAST INTO NORTH-CENTRAL SD TO EASTERN
   ND.  THE AIR MASS FROM CENTRAL/WESTERN NEB THROUGH CENTRAL SD HAS
   BECOME MODERATELY UNSTABLE WITH SOME INCREASE IN BULK SHEAR
   EXPECTED.  GIVEN THE LIKELIHOOD FOR ONGOING STORMS AND ADDITIONAL
   STORM DEVELOPMENT TO SPREAD INTO CENTRAL SD THROUGH THIS EVENING...A
   NEW WW WILL BE NEEDED...WITH THAT ISSUANCE POSSIBLE SOONER...IF
   STRONGER STORM INTENSITIES IN NORTHERN PART OF 465 ARE SUSTAINED IN
   THE SHORT TERM.  SEVERE HAIL AND DAMAGING WINDS WILL BE THE PRIMARY
   THREATS DOWNSTREAM OF WW 465.

   ..PETERS/HART.. 09/04/2016


   ATTN...WFO...FSD...ABR...UNR...

   LAT...LON   44720114 45939946 45889878 45919784 44749809 43659849
               43359888 43169928 43630037 44040109 44720114