MESOSCALE DISCUSSION 1959
   NWS STORM PREDICTION CENTER NORMAN OK
   0344 PM CDT FRI AUG 12 2011
   
   AREAS AFFECTED...ERN ND...NERN SD...WRN/NRN MN
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 771...
   
   VALID 122044Z - 122215Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 771
   CONTINUES.
   
   AN ORGANIZING QLCS JUST EAST OF A SFC LOW AND COLD FRONT OVER CNTRL
   ND IS MOVING EWD AROUND 20 KT. ELY TO SELY FLOW AROUND 10 KT BELOW 2
   KM AGL PER GRAND FORKS VWP DATA WILL ENHANCE LOW-LEVEL INFLOW INTO
   THIS SYSTEM...WHICH WILL LIKELY BE SUSTAINED AS IT MOVES INTO AN AIR
   MASS CHARACTERIZED BY MODERATE INSTABILITY OVER ERN ND. SUFFICIENT
   DEEP-LAYER FORCING FOR ASCENT AND MID-LEVEL HEIGHT FALLS IN
   ASSOCIATION WITH A COMPACT VORT MAX...CURRENTLY TRANSLATING ESEWD
   OVER CNTRL ND...WILL LIKELY COMPENSATE FOR THE MODEST VERTICAL SHEAR
   IN PLACE ACROSS ND. DMGG WIND GUSTS WILL BE OF CONCERN WITH THIS
   ACTIVITY...WITH NOTABLE MID-ALTITUDE RADIAL CONVERGENCE SIGNATURES
   ALREADY NOTED IN BISMARCK ND 0.5-DEGREE SRM DATA. THIS THREAT WOULD
   BE BOLSTERED IF A MESOSCALE COLD POOL DEVELOPS AND SYSTEM
   ACCELERATION OCCURS. LARGE HAIL WILL ALSO BE POSSIBLE. WITH THE
   ABSENCE OF STRONGER AMBIENT LOW-LEVEL FLOW...AND WITH A PRIMARILY
   LINEAR CONVECTIVE MODE...THE TORNADO POTENTIAL SHOULD BE MINIMAL.
   
   FARTHER SOUTH INTO NERN SD...SUFFICIENT MOISTURE CONVERGENCE ALONG
   THE SWWD-ARCING COLD FRONT AND ALONG A NW/SE-ORIENTED PREFRONTAL
   TROUGH COULD PROVIDE ADDITIONAL CONVECTIVE SUPPORT SOUTH OF THE
   QLCS. VISIBLE SATELLITE IMAGERY REVEALS SOME BOUNDARY-LAYER CUMULUS
   DEVELOPMENT IN THESE AREAS...WITH THE POTENTIAL FOR DEEPER
   CONVECTION TO DEVELOP WITH THE GLANCING INFLUENCE OF THE VORT MAX.
   GIVEN MLCAPE VALUES OF 1000-2000 J/KG...AIDED BY THE NWD EXTENSION
   OF THE EML INTO THE ERN PERIPHERY OF THE VORT MAX...AND SOMEWHAT
   GREATER DEEP-LAYER SHEAR -- I.E. EFFECTIVE BULK SHEAR MAGNITUDES OF
   25-30 KT -- LARGE HAIL AND DMGG WIND GUSTS WOULD ENSUE WITH
   MULTICELLS.
   
   THE SVR THREAT COULD SHIFT EAST OF WW771 BY 00Z...AND PORTIONS
   W-CNTRL MN WILL BE MONITORED FOR THE POSSIBLE ISSUANCE OF A WW. ALSO
   OF NOTE...FROM N-CNTRL MN INTO THE MN ARROWHEAD...LOW-LEVEL
   CONVERGENCE ALONG A STATIONARY FRONT...COMBINED WITH MLCAPE VALUES
   OF 1000-1500 J/KG...COULD SUPPORT ISOLATED STRONG STORMS OR POSSIBLY
   A SVR STORM. HOWEVER...WITH THE STRONGER FORCING FOR ASCENT
   REMAINING TO THE WEST OF THIS AREA THROUGH 00Z...THE SVR THREAT WILL
   LIKELY BE LIMITED THROUGH LATE AFTERNOON.
   
   ..COHEN.. 08/12/2011
   
   
   ATTN...WFO...DLH...MPX...FGF...FSD...ABR...BIS...
   
   LAT...LON   44509703 44709871 45299951 47059976 47869986 48379963
               48549912 48659838 48509747 48529680 48809598 48939505
               48719388 48379231 47949119 47449161 47369389 46179489
               45159499 44609590 44509703