MESOSCALE DISCUSSION 0338
   NWS STORM PREDICTION CENTER NORMAN OK
   0759 PM CDT MON MAR 30 2009
   
   AREAS AFFECTED...N CNTRL NEB...CNTRL AND ERN SD...SERN ND
   
   CONCERNING...BLIZZARD 
   
   VALID 310059Z - 310500Z
   
   HEAVY SNOW/BLIZZARD CONDITIONS ARE ONGOING ACROSS PORTIONS OF
   NEB...SD...AND ND...AND WILL CONTINUE TO GRADUALLY SHIFT EWD OVER
   THE NEXT FEW HOURS. STRONG NELY/NLY SURFACE WINDS WITH GUSTS TO 45
   MPH WILL CAUSE CONSIDERABLE RESTRICTIONS IN VISIBILITY IN BLOWING
   SNOW. 
   
   994 MB SURFACE LOW IS NOW LOCATED ROUGHLY OVER NERN NEB AS OF 00Z.
   SURFACE FREEZING LINE RUNS FROM NEAR MOORHEAD MN WSWWD THROUGH
   ABERDEEN SD...THEN SWWD TO AINSWORTH NEB. AREA OF HEAVIEST
   SNOWFALL...ROUGHLY THROUGH SERN ND INTO THE BLACK HILLS OF SD WILL
   SHIFT EWD WITH TIME...WHILE HIGHER RATES OF SNOWFALL CAN BE
   ANTICIPATED. DEFORMATION AXIS IS NOW IN THE PROCESS OF REFORMING AS
   A STRONG VORTICITY MAXIMUM...SEEN ON WV IMAGERY MOVING INTO S CNTRL
   NEB...CONTINUES TO TRANSLATE NEWD...WHILE UPPER DIVERGENCE BECOMES
   MAXIMIZED OVER THE NRN PLAINS. DIURNAL COOLING...LOW LEVEL CAA...AND
   EVAPORATIONAL COOLING FROM ONGOING PRECIPITATION SHOULD ALLOW THE
   SURFACE FREEZING LINE TO MIGRATE EWD WITH A TRANSITION TO ALL SNOW
   LIKELY BY 06Z.
   
   A 40 TO 50 KT LOW LEVEL JET HAS ALLOWED RAPID NWD TRANSPORT OF
   MOISTURE...SOMEWHAT REFLECTED IN A 12Z/00Z SOUNDING COMPARISON AT
   OAX WHERE A 0.10 INCH PWAT INCREASE HAS BEEN MEASURED...WHILE GOES
   PWAT DATA SHOWS HIGHER VALUES HAVE MOVED INTO SD. ALREADY SATURATED
   PROFILES WILL UNDERGO INCREASING MOISTURE CONTENT...WHICH WILL
   CONTRIBUTE TO INCREASING SNOW RATES AS THE AFOREMENTIONED
   DEFORMATION AXIS RESTRENGTHENS...AND STRONG JET DYNAMICS AID
   VERTICAL MOTION. COOLING TEMPERATURES ALOFT WILL LEAD TO A WEAK
   LAYER OF ELEVATED INSTABILITY...WHICH COULD FURTHER ENHANCE RATES IN
   THUNDERSNOW...ESPECIALLY OVER PORTIONS OF ERN SD NEAR 06Z.
   
   ..HURLBUT.. 03/31/2009
   
   
   ATTN...WFO...FGF...FSD...ABR...BIS...LBF...UNR...
   
   LAT...LON   42949833 41749974 41990115 43690118 45110030 46499876
               46299721 45319739 43819859 42949833