MESOSCALE DISCUSSION 0217
   NWS STORM PREDICTION CENTER NORMAN OK
   1141 AM CST WED FEB 28 2007
   
   AREAS AFFECTED...PARTS OF ERN SD INTO SWRN MN
   
   CONCERNING...HEAVY SNOW 
   
   VALID 281741Z - 282145Z
   
   MODERATE TO HEAVY SNOWFALL RATES ARE EXPECTED TO DEVELOP FROM SW-NE
   ACROSS ERN SD INTO SWRN MN THIS AFTERNOON...WITH RATES GENERALLY
   AROUND 1 IN/HR.  EMBEDDED CONVECTION SHOULD ENHANCE SNOWFALL RATES
   UP TO 2+ IN/HR.
   
   WATER VAPOR IMAGERY INDICATED A SHORT WAVE TROUGH OVER THE NRN HIGH
   PLAINS WHICH IS FORECAST TO MOVE SLOWLY NWD...RESULTING IN FAVORABLE
   DOWNSTREAM ASCENT WITHIN DIFFLUENT FLOW REGIME REMAINING OVER THE
   ERN DAKOTAS/SWRN MN THROUGH THE AFTERNOON.  MEANWHILE...LOW LEVEL
   WAA ALONG SELY LLJ EXTENDING FROM IA TO ERN SD IS ENHANCING THE DEEP
   LAYER ASCENT ACROSS THE MESOSCALE DISCUSSION AREA.  IR IMAGERY
   INDICATED AN EXPANDING AREA OF COLD CLOUD TOPS OVER SERN SD WITH A
   FEW EMBEDDED TSTMS PER LIGHTNING DATA...WITH BOTH OF THESE
   OBSERVATIONS INDICATIVE OF THE STRONG DEEP LAYER ASCENT UNDERWAY
   ACROSS THIS REGION.
   
   15Z RUC FORECAST SOUNDINGS SUGGEST A DEEP LOW LEVEL SUB 0 C
   ISOTHERMAL LAYER SHOULD EXIST OVER ERN SD/SWRN MN THIS AFTERNOON
   FAVORING AGGREGATE SNOW GROWTH...WHILE WEAK INSTABILITY ROOTED NEAR
   600-700 MB MAY RESULT IN A FEW EMBEDDED TSTMS FURTHER ENHANCING
   SNOWFALL RATES.
   
   ..PETERS.. 02/28/2007
   
   
   ATTN...WFO...MPX...FSD...ABR...
   
   44049587 43639598 43129658 42999717 43419764 44399827
   44909853 45369833 45629741 45589692 44969617