MESOSCALE DISCUSSION 0440
   NWS STORM PREDICTION CENTER NORMAN OK
   0240 AM CDT THU APR 11 2013
   
   AREAS AFFECTED...SRN MN...ERN SD...NWRN IA...EXTREME WRN WI
   
   CONCERNING...HEAVY SNOW 
   
   VALID 110740Z - 111215Z
   
   SUMMARY...MODERATE/OCCASIONALLY HEAVY SNOW WILL INCREASE IN COVERAGE
   EARLY THIS MORNING...WITH RATES OF 1-1.5 IN/HR POSSIBLE. IN AREAS
   WHERE SNOW IS NOT ALREADY UNDERWAY...RAIN/SLEET IS EXPECTED TO
   CHANGE TO SNOW BY 09-10Z.
   
   DISCUSSION...LATEST WV IMAGERY DEPICTS A CLOSED UPPER LOW MOVING
   SLOWLY ENEWD ACROSS THE CENTRAL PLAINS...WITH MULTIPLE EMBEDDED
   VORTICITY MAXIMA ROTATING WITHIN THE LARGER CIRCULATION. ONE OF
   THESE EMBEDDED FEATURES IS CURRENTLY PROGRESSING NWD ACROSS THE MO
   VALLEY OF ERN NE/WRN IA. AHEAD OF THIS FEATURE...INCREASING ASCENT
   HAS RESULTED IN AN EXPANDING SHIELD OF PRECIPITATION WITH LOCALLY
   MODERATE/HEAVY SNOW ALREADY REPORTED. STEEP LAPSE RATES OF AROUND 7
   DEG C/KM IN THE 3-6 KM LAYER /SAMPLED UPSTREAM IN THE 00Z DDC
   SOUNDING AND ALSO DEPICTED IN AVAILABLE FCST SOUNDINGS/ WILL FAVOR
   SOME CONVECTIVE ENHANCEMENT OF PRECIPITATION RATES.
   
   SNOW IS ALREADY FALLING ACROSS ERN SD INTO SWRN MN AND NWRN IA.
   AREAS FURTHER TO THE EAST ACROSS S-CENTRAL AND SE MN ARE CURRENTLY
   REPORTING A MIXTURE OF RAIN AND SLEET...DUE TO A COMBINATION OF
   ABOVE FREEZING SFC TEMPS AND A WARM NOSE IN THE 800-700 MB LAYER.
   WHILE SIGNIFICANT COOLING OF THE WARM NOSE IS NOT EXPECTED...RECENT
   HI-RES GUIDANCE /NOTABLY THE EXPERIMENTAL 11/00Z SSEO AND 11/04Z
   HRRR/ AND FCST SOUNDINGS SUGGEST SUFFICIENT LIFT WILL OCCUR TO COOL
   THE COLUMN AND ALLOW THE PRECIP TYPE TO BECOME PREDOMINATELY SNOW BY
   09-10Z...THOUGH A MIXTURE OF SLEET MAY PERSIST LONGER OUTSIDE OF
   HEAVIER PRECIP BANDS. MEANWHILE...ADVECTION OF COLD/DRY AIR IN THE
   LOW LEVELS WILL ALLOW TEMPS TO FALL TO NEAR OR BELOW FREEZING. 
   
   SNOWFALL RATES OF 1-1.5 IN/HR WILL BE POSSIBLE THROUGH 12Z...WITH A
   SLOW DIMINISHING OF PRECIP FROM SW TO NE EXPECTED AFTER 09Z AS THE
   DRY SLOT IN THE WAKE OF THE EMBEDDED VORT MAX APPROACHES THE
   AREA...THOUGH PRECIP WILL LINGER WELL PAST 12Z ACROSS THE ERN
   PORTION OF THE MCD AREA.
   
   ..DEAN.. 04/11/2013
   
   
   ATTN...WFO...ARX...MPX...DMX...FGF...FSD...ABR...
   
   LAT...LON   42429493 42859650 43699730 44429798 45279784 45879679
               45829518 45749401 45519286 45139205 44369163 43739217
               42949321 42479414 42429493