MESOSCALE DISCUSSION 1501
   NWS STORM PREDICTION CENTER NORMAN OK
   0351 PM CDT MON JUL 04 2011
   
   AREAS AFFECTED...SWRN...CNTRL AND N-CNTRL SD
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 042051Z - 042145Z
   
   WEAK UPSLOPE FLOW HAS AIDED IN THE INITIATION OF TSTMS OVER THE
   BLACK HILLS OF SWRN SD. FURTHER CONVECTIVE DEVELOPMENT ALONG A
   SLOW-MOVING COLD FRONT IS POSSIBLE LATER THIS
   AFTERNOON/EVENING...AND COULD EVENTUALLY REQUIRE ISSUANCE OF A WW.
   
   SFC ANALYSIS FROM 20Z PLACES A COLD FRONT FROM 25 NW MBG TO 30 S
   RAP. A VERY HOT/MOIST BOUNDARY LAYER IS IN PLACE ALONG/AHEAD OF THE
   COLD FRONT...WHERE SFC DEW POINTS ARE IN THE LOWER-MID 70S ARE IN
   PLACE. UPPER RIDGE AXIS IS CURRENTLY POSITIONED OVERHEAD /PER RECENT
   WATER VAPOR IMAGERY/ AND MAY BE CONTRIBUTING TO WEAK CINH WHICH HAS
   LIKELY PREVENTED TSTM DEVELOPMENT OVER THE PLAINS THUS FAR. WITH
   TIME...UPPER RIDGE SHOULD SLOWLY SHIFT EWD...WITH GRADUAL EROSION OF
   CINH LEADING TO A MORE FAVORABLE ENVIRONMENT FOR DISCRETE TSTMS.
   GIVEN THE PRESENCE OF RICH BOUNDARY LAYER THETA-E...STEEP MIDLEVEL
   LAPSE RATES...AND MLCAPE VALUES EVENTUALLY INCREASING TO 3000-4000
   J/KG...A THREAT /CONDITIONAL ON TSTM DEVELOPMENT/ FOR LARGE HAIL AND
   DMGG WIND GUSTS SHOULD MATERIALIZE. DESPITE WEAKNESS IN FLOW
   THROUGHOUT THE LOWER HALF OF THE TROPOSPHERE...MIDLEVEL WLYS ATOP
   S-SELY LOW-LEVEL FLOW SHOULD LEAD TO EFFECTIVE SHEAR VALUES /NEAR 30
   KTS/ MARGINALLY SUPPORTIVE OF SUPERCELL STRUCTURES.
   
   FARTHER UPSTREAM...AN UPPER IMPULSE OVER N-CNTRL WY WILL EVENTUALLY
   SHIFT INTO THE NRN HIGH PLAINS...AND SHOULD RESULT IN AN EXPECTED
   UPSWING IN CONVECTIVE COVERAGE THIS EVENING AS INCREASING FORCED
   ASCENT OVERSPREADS THE SFC COLD FRONT.
   
   ..ROGERS.. 07/04/2011
   
   
   ATTN...WFO...ABR...UNR...CYS...
   
   LAT...LON   45249897 43809981 43000135 42990288 43230363 43720403
               44860224 45690139 45930026 45889910 45819879 45249897