MESOSCALE DISCUSSION 1494
   NWS STORM PREDICTION CENTER NORMAN OK
   0136 PM CDT MON JUL 16 2007
   
   AREAS AFFECTED...EASTERN SD/SOUTHERN MN INTO NORTHERN IA
   
   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 
   
   VALID 161836Z - 162030Z
   
   SEVERE THREAT IS EXPECTED TO STEADILY INCREASE ACROSS EASTERN SD
   INTO SOUTHERN MN/NORTHERN IA THROUGH MID/LATE AFTERNOON. A WATCH
   WILL LIKELY BE NEEDED...POTENTIALLY WITHIN THE HOUR.
   
   WATER VAPOR IMAGERY FEATURES MID LEVEL IMPULSE ADVANCING
   SOUTHEASTWARD ACROSS ND/NORTHERN SD EARLY THIS AFTERNOON. AT THE
   SURFACE...ROUGHLY WNW-ESE ORIENTED STATIONARY FRONTAL BOUNDARY IS
   ANALYZED FROM NORTHERN SD TO SOUTHERN MN/NORTHEAST IA. IT IS
   ANTICIPATED THIS FRONTAL ZONE WILL GENERALLY SERVE AS THE PRIMARY
   FOCUS FOR INCREASING THUNDERSTORM COVERAGE/SEVERE THREAT REMAINDER
   OF THE AFTERNOON/EARLY EVENING.
   
   ASSOCIATED WITH THE AFOREMENTIONED MID LEVEL IMPULSE...ELEVATED
   THUNDERSTORMS HAVE BEEN COMMON SINCE THIS MORNING FROM ND INTO
   NORTHEAST SD. LATEST VOLUMETRIC RADAR IMAGERY SUGGESTS SOME
   INTENSIFICATION HAS OCCURRED OVER THE PAST HOUR ACROSS NORTHEAST SD
   NEAR AND EAST OF ABERDEEN. WITH STORMS EXPECTED TO CONTINUE
   DEVELOPING/EXPANDING SOUTHEASTWARD THROUGH THE AFTERNOON...MODIFIED
   12Z ABERDEEN SD RAOB AND AVAILABLE AMDAR DATA/RUC FORECAST SOUNDINGS
   SUGGEST POTENTIAL SURFACE BASED STORMS/NEGLIGIBLE CINH WILL LIKELY
   BE ACHIEVED AS TEMPERATURES REACH 90 F. THESE DATA SUGGEST THE
   POTENTIAL FOR MLCAPES TO REACH 1500-2000 J/KG THIS AFTERNOON ACROSS
   MUCH OF THE CORRIDOR...WITH HIGHER DOWNSTREAM VALUES ACROSS NORTHERN
   IA WHERE UPPER 60S F/LOWER 70S F DEWPOINTS RESIDE.
   
   WOOD LAKE MN PROFILER AND REGIONAL WSR-88D VWP DATA CONFIRMS
   RELATIVELY STRONG DEEP LAYER SHEAR...WITH 40-50 KT OF EFFECTIVE BULK
   SHEAR MAXIMIZED ALONG/NORTHEAST OF THE QUASI-STATIONARY FRONT. AMPLE
   VEERING/SPEEDS WILL SUPPORT ROTATING STORMS/SUPERCELLS. LARGE
   HAIL/DAMAGING WIND GUSTS WILL LIKELY BE THE PRIMARY RISKS...WITH
   POSSIBLE UPSCALE EVOLUTION INTO A SEVERE MCS BY LATE THIS
   AFTERNOON/EARLY EVENING. AN ISOLATED TORNADO THREAT MAY EXIST AS
   WELL...PARTICULARLY WITH ANY QUASI-DISCRETE CELLS THAT DEVELOP AHEAD
   OF THE PRIMARY CONVECTIVE LINE.
   
   ..GUYER.. 07/16/2007
   
   
   ATTN...WFO...ARX...MPX...DMX...FSD...ABR...
   
   45509719 45509572 44259273 42869285 42409426 42829594
   44389771 45029786