MESO: Mesoscale Discussion 0334

ACUS11 KWNS 302021
SWOMCD
SPC MCD 302020
MNZ000-SDZ000-NDZ000-NEZ000-310215-

MESOSCALE DISCUSSION 0334
NWS STORM PREDICTION CENTER NORMAN OK
0320 PM CDT MON MAR 30 2009

AREAS AFFECTED...SRN ND / MUCH OF SD / N-CNTRL INTO NERN NEB

CONCERNING...HEAVY SNOW

VALID 302020Z - 310215Z

LOWER TO MID TROPOSPHERIC FRONTOGENETICAL FORCING HAS MAINTAINED A
WELL-DEFINED HEAVY SNOW BAND TODAY ACROSS PORTIONS OF WRN SD INTO
S-CNTRL AND SERN ND. RECENT TRENDS IN REGIONAL RADAR DATA INDICATE
THAT THIS BAND IS SLOWLY PIVOTING CYCLONICALLY...WITH HEAVIEST SNOW
EXTENDING FROM LOGAN AND MCINTOSH COUNTIES IN S-CNTRL ND TO
PENNINGTON...HAAKON INTO JACKSON COUNTIES IN WRN SD AS OF 20Z.

LATEST MODEL GUIDANCE SUGGESTS THAT THIS DEFORMATION BAND MAY
TEMPORARILY WEAKEN LATER THIS AFTERNOON BEFORE REFORMING BETWEEN
31/00-06Z FROM N-CNTRL NEB INTO NERN SD. THIS EVOLUTION WILL OCCUR
AS STRONG VORTICITY MAXIMUM TRANSLATES NEWD FROM THE CNTRL HIGH
PLAINS...SUPPORTING THE EWD MIGRATION OF MID TO UPPER-LEVEL LOW
CENTER INTO NEB TONIGHT. MEANWHILE...ATTENDANT SURFACE LOW /LOCATED
S OF GRI AS OF 19Z/ WILL GRADUALLY UNDERGO OCCLUSION WHILE
DEVELOPING NNEWD INTO NERN NEB.

LATEST GOES SOUNDER AND GPS PW DATA INDICATE MOISTURE GRADUALLY
INCREASING NWD THROUGH THE OZARK PLATEAU INTO LOWER MO VALLEY ALONG
40-50 KT LLJ. WITH TIME...THE NRN EXTENT OF THIS MOISTURE AXIS WILL
BECOME ENTRAINED WITHIN THE DEEP-LAYER CYCLONE...EFFECTIVELY
ENHANCING PRECIPITATION RATES WITHIN EVOLVING DEFORMATION BAND.
WHILE AIR MASS OVER NERN SD INTO N-CNTRL NEB IS CURRENTLY ABOVE
FREEZING AT MOST LOCATIONS...THE COMBINATION OF DIURNAL COOLING THIS
EVENING IN CONJUNCTION WITH LOW-LEVEL CAA AND EVAPORATION/MELTING
EFFECTS SHOULD EVENTUALLY SUPPORT SNOW WITHIN THE ZONE OF STRONGEST
FRONTOGENETICAL FORCING/DEEP-LAYER ASCENT. HERE...LOCAL RATES WILL
BEGIN TO APPROACH ONE INCH PER HOUR BETWEEN 31/03-06Z.

..MEAD.. 03/30/2009

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...FGF...FSD...OAX...ABR...BIS...LBF...UNR...

LAT...LON 43160243 44560216 45860090 46410005 46619927 46349723
45049649 43739763 42399859 42199973 42350126 43160243

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