MESOSCALE DISCUSSION 0039
   NWS STORM PREDICTION CENTER NORMAN OK
   1138 PM CST TUE JAN 13 2009
   
   AREAS AFFECTED...ERN IA...SWRN WI...NRN IL...NWRN INDIANA
   
   CONCERNING...HEAVY SNOW 
   
   VALID 140538Z - 140945Z
   
   A SWATH OF MODERATE TO HEAVY SNOWFALL WILL CONTINUE TO MOVE ESEWD
   BEFORE WEAKENING OVER NWRN/CNTRL INDIANA NEAR 12Z. INCH AN HOUR
   RATES WILL BE LIKELY MAINLY ACROSS ERN IA AND NWRN/CNTRL IL.
   
   A VORT MAX ROTATING AROUND THE BACKSIDE OF A LARGER SCALE TROUGH IS
   NOW PRESSING ESEWD INTO SWRN WI/IL. MODERATE TO HEAVY SNOWFALL HAS
   BEEN OBSERVED OVER ERN IA...AND THE HEAVIEST SNOW BAND IS NOW
   ORIENTED N-S NEAR THE IA/IL BORDER AND MOVING EWD. DESPITE VERY LOW
   PWAT AND AVAILABLE MOISTURE...ISENTROPIC LIFT IN COMBINATION WITH
   SUPPORT FROM THE VORT MAX IS CONTRIBUTING TO VERTICAL MOTION AND
   AFOREMENTIONED SNOWFALL RATES. 05Z SURFACE ANALYSIS REFLECTS A WEAK
   WARM FRONT EXTENDING EWD FROM A SURFACE LOW IN WRN IA...RUNNING
   ALONG THE IA/MO BORDERS AND INTO CNTRL IL. VAD WIND PROFILE DATA
   SUGGESTS THE STRONGEST LOW LEVEL WARM ADVECTION IS JUST N OF THIS
   FRONT IN A SMALL AREA FROM ERN IA INTO CNTRL/NWRN IL. EXPECT THE
   HIGHEST ACCUMULATIONS TO BE IN THESE AREAS OVER THE NEXT FEW HOURS.
   RATES WILL GRADUALLY DECREASE AS THE LOW AND ASSOCIATED ISENTROPIC
   LIFT BEGIN TO WEAKEN.
   
   ..HURLBUT.. 01/14/2009
   
   
   ...NOTICE...
   SPC WINTER WEATHER MESOSCALE DISCUSSIONS WILL BE ISSUED ON A
   SCHEDULED BASIS FROM DECEMBER 1 THROUGH FEBRUARY 28...FOUR
   TIMES A DAY...AROUND 00 UTC...06 UTC...12 UTC...AND 18 UTC
   FOR SIGNIFICANT SHORT RANGE WINTER WEATHER EVENTS.
   
   ATTN...WFO...IWX...IND...LOT...ILX...MKX...LSX...DVN...ARX...
   DMX...
   
   LAT...LON   40198575 39528924 40519195 42009349 42919341 43479215
               43139007 42418805 41608690 40938580 40198575