MESOSCALE DISCUSSION 0527
   NWS STORM PREDICTION CENTER NORMAN OK
   0557 PM CDT SAT APR 21 2007
   
   AREAS AFFECTED...EXTREME NERN CO...SWRN AND CENTRAL NEB
   
   CONCERNING...TORNADO WATCH 154...
   
   VALID 212257Z - 220100Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 154 CONTINUES.
   
   A FEW STRONG SUPERCELLS HAVE BEEN MOVING THRU CHERRY COUNTY...AND
   ACROSS NERN CO OVER THE PAST FEW HOURS.  THE ACTIVITY OVER ERN
   CHERRY COUNTY IS BEING ENHANCED BY A CONVECTIVE OUTFLOW BOUNDARY AS
   WELL AS VERY STRONG SFC/LOW LEVEL FLOW.  THE ACTIVITY IS MOVING NEWD
   INTO INCREASING 0-1 KM HELICITY WHERE VALUES ARE 150-200 M2/S2 WHICH
   WILL ENHANCE STORM RELATIVE FLOW INTO THE SUPERCELL MOVING NEWD OVER
   ERN CHERRY COUNTY.
   
   OVERALL...THE ENVIRONMENT REMAINS VERY FAVORABLE FOR SUSTAINING
   UPDRAFTS/SUPERCELLS ESPECIALLY NEAR THE BOUNDARIES AS MLCAPE IS VERY
   UNSTABLE WITH VALUES BETWEEN 1500-2500 J/KG AND DEEP LAYER SHEAR OF
   45-55 KT.  GIVEN THE CURRENT RADAR...MAIN THREAT AREAS WILL BE FROM
   ERN CHERRY COUNTY NEWD INTO BROWN AND KEYA PAHA NEB...THEN TRIPP AND
   GREGORY COUNTIES IN SD IN WW 155.  ALSO..THE LARGE SUPERCELL OVER
   SEDGWICK AND PHILLIPS COUNTIES IN CO SHOULD MOVE INTO KEITH AND
   PERKINS COUNTIES IN NEB DURING THE NEXT SEVERAL HOURS.
   
   ..MCCARTHY.. 04/21/2007
   
   
   ATTN...WFO...FSD...GID...LBF...UNR...GLD...BOU...CYS...
   
   40430265 40900265 41080260 41560263 42000265 42040200
   42670205 42990195 42940015 42999932 42979843 42709832
   42089830 41739832 41709879 41329878 41099880 41019922
   40699947 40419965 40380003 40420045 40390129 40300204
   40400211 40430261