MESOSCALE DISCUSSION 0343
   NWS STORM PREDICTION CENTER NORMAN OK
   0122 AM CDT TUE MAR 31 2009
   
   AREAS AFFECTED...FAR N CNTRL NEB...ERN SD...SERN ND...W CNTRL MN
   
   CONCERNING...BLIZZARD 
   
   VALID 310622Z - 311015Z
   
   A SW TO NE ORIENTED BAND OF HEAVY SNOW/BLIZZARD CONDITIONS ACROSS N
   CNTRL NEB...ERN SD...SERN ND...AND W CNTRL MN WILL GRADUALLY SHIFT
   EWD WHILE ALSO BUILDING NEWD INTO MN. STRONG NELY/NLY SURFACE WINDS
   WITH GUSTS TO 50 MPH WILL CAUSE CONSIDERABLE RESTRICTIONS IN
   VISIBILITY IN BLOWING SNOW. 
   
   A 995 MB SURFACE LOW NEAR THE NEB/IA/SD BORDERS HAS MADE LITTLE
   MOVEMENT OVER THE PAST FEW HOURS...WHILE THE SURFACE FREEZING LINE
   HAS MIGRATED EWD SOMEWHAT DUE TO THE EFFECTS OF DIURNAL
   COOLING...LOW LEVEL COLD ADVECTION...AND EVAPORATIONAL COOLING FROM
   LIGHT PRECIPITATION AHEAD OF THE MAIN BAND OF SNOW. AS THE SURFACE
   LOW GRADUALLY MOVES NEWD OVER THE NEXT FEW HOURS...THESE EFFECTS
   WILL CAUSE THE SURFACE FREEZING LINE TO SHIFT EWD ACROSS
   SD/NEB...AND SWD INTO MN...AND A TRANSITION FROM RAIN TO SNOW WILL
   ENSUE. 
   
   A STRONG VORTICITY MAXIMUM NOTED ON WV IMAGERY OVER NERN NEB/SERN
   SD...AND FAVORABLE UPPER DIVERGENCE/JET DYNAMICS HAVE MAINTAINED A
   STRONG DEFORMATION AXIS OVER N CNTRL NEB...ERN SD...SERN ND...AND W
   CNTRL MN. AS THE UPPER LOW BEGINS TO TRANSLATE EWD THEN NEWD...THIS
   DEFORMATION AXIS WILL SLOWLY SHIFT EWD...WITH HEAVY SNOWFALL
   DECREASING SLIGHTLY IN N CNTRL NEB. HIGHER RATES WILL CONTINUE
   ACROSS ERN SD AND SERN ND...AND INCREASE THROUGH W CNTRL MN. COOLING
   ALOFT HAS ALLOWED A WEAK LAYER OF ELEVATED INSTABILITY TO
   DEVELOP...AND OCCASIONAL LIGHTNING STRIKES HAVE BEEN OBSERVED ACROSS
   ERN SD. EXPECT ERN SD AND W CNTRL MN TO BE THE FAVORED AREAS FOR
   CONVECTIVE SNOW BURSTS...WITH LOCAL RATES OF 2 TO 3 INCHES AN HOUR.
   
   ..HURLBUT.. 03/31/2009
   
   
   ATTN...WFO...DLH...MPX...FGF...FSD...ABR...BIS...LBF...UNR...
   
   LAT...LON   43819767 42949887 42539996 42800056 43730034 45029969
               45989863 46849670 47059506 46529416 45579490 43819767