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Mesoscale Discussion 681
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   MESOSCALE DISCUSSION 0681
   NWS STORM PREDICTION CENTER NORMAN OK
   0635 PM CDT SUN MAY 22 2016

   AREAS AFFECTED...SOUTHWEST TO NORTH-CENTRAL NEBRASKA INTO CENTRAL SD

   CONCERNING...TORNADO WATCH 191...

   VALID 222335Z - 230130Z

   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 191 CONTINUES.

   SUMMARY...ALL SEVERE HAZARDS REMAIN THREATS WITHIN TORNADO WATCH 191
   THROUGH THIS EVENING ACROSS SOUTHWEST INTO NORTH-CENTRAL NEBRASKA TO
   CENTRAL SD.  THE TORNADO RISK SHOULD REMAIN THE GREATEST ACROSS THE
   NEBRASKA PORTION OF THIS WATCH...AND ESPECIALLY ON THE SOUTHERN
   FLANK OF THE CLUSTER OF STORMS THAT HAVE TENDED TO BE ANCHORED OVER
   NORTH-CENTRAL/NORTHEAST CHERRY COUNTY NEB AND PORTIONS OF TODD
   COUNTY SD.

   DISCUSSION...TRENDS IN MOSAIC RADAR IMAGERY SHOWED A SMALL CLUSTER
   OF STORMS CENTERED ALONG AND EITHER SIDE OF THE SD/NEB BORDER FROM
   NORTHERN CHERRY COUNTY NEB TO SOUTHERN TODD COUNTY SD.  RADAR AND
   SATELLITE IMAGERY AND SURFACE ANALYSIS SHOWED A CONVERGENCE ZONE
   EXTENDING FROM HITCHCOCK COUNTY NEB THROUGH LINCOLN COUNTY NEB /JUST
   WEST OF LBF/ TO THE WESTERN EDGE OF THE NEB/SD CLUSTER OF
   STORMS...AND THEN FARTHER NORTHWARD THROUGH CENTRAL SD.  THIS
   BOUNDARY WAS LOCATED WITHIN A CORRIDOR OF MODERATELY STRONG TO VERY
   STRONG INSTABILITY /MLCAPE OF 1500-3000 J PER KG/...WITH A NEW STORM
   DEVELOPING IN LINCOLN COUNTY NEB.  MEANWHILE...UPDRAFTS ALONG THE
   CONVERGENCE ZONE CONTINUE TO TRACK NORTHWARD AND MATURE AS THEY
   REACH THE SOUTHERN EXTENT OF THE SD/NEB BORDER COMPLEX IN NORTHERN
   CHERRY COUNTY NEB.  SINCE 2155Z...SURFACE WINDS FROM NEAR /AT VTN/
   AND SOUTHEAST THROUGH NORTHEAST OF THE SD/NEB BORDER TSTM COMPLEX
   BACKED TO SOUTHEASTERLY AND HAVE INCREASED SOME...ENHANCING
   LOW-LEVEL HODOGRAPH CURVATURE.  MODIFYING THE 23Z RAP FORECAST WITH
   SURFACE WINDS AT WINNER SD RESULTED IN AN INCREASE IN LOW-LEVEL AND
   DEEP-LAYER SHEAR /SFC-1 KM SHEAR AROUND 30 KT...EFFECTIVE SRH OF 250
   M2/S2 AND EFFECTIVE BULK SHEAR AROUND 40 KT/.  THIS CAPE/SHEAR
   PARAMETER SPACE SUGGESTS THE TORNADO THREAT WILL PERSIST WITH STORMS
   ALONG THE SOUTHERN AND EASTERN FLANKS OF THE AFOREMENTIONED TSTM
   CLUSTER.

   ADDITIONAL STORMS SHOULD CONTINUE TO DEVELOP SOUTHWARD IN VICINITY
   OF THE CONVERGENCE ZONE IN WEST-CENTRAL TO SOUTHWEST NEB WITH BULK
   SHEAR CROSSING THIS BOUNDARY AND VERY STRONG INSTABILITY WILL
   SUPPORT ALL SEVERE HAZARDS.

   MEANWHILE...LEFT SPLITS TRACKING NORTHWARD ACROSS CENTRAL SD SHOULD
   TEND TO PRODUCE HAIL AS THE PRIMARY THREATS BEFORE WEAKENING.

   ..PETERS.. 05/22/2016


   ATTN...WFO...FSD...ABR...LBF...UNR...BOU...

   LAT...LON   40690200 41140243 42690249 43030210 44510183 44810046
               44520006 43899936 43539930 43019953 42530014 41270021
               40700030 40690200 

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