MESO: Mesoscale Discussion 0079

ACUS11 KWNS 092352
SWOMCD
SPC MCD 092352
NDZ000-SDZ000-100345-

MESOSCALE DISCUSSION 0079
NWS STORM PREDICTION CENTER NORMAN OK
0552 PM CST MON FEB 09 2009

AREAS AFFECTED...WRN ND THROUGH NW SD

CONCERNING...HEAVY SNOW

VALID 092352Z - 100345Z

OCCASIONAL SNOWFALL RATES LOCALLY UP TO 1 INCH PER HOUR WILL REMAIN
POSSIBLE FROM NW SD THROUGH WRN ND THIS EVENING.

DEEP SURFACE LOW OVER S CNTRL SD EMBEDDED WITHIN DIVERGENT REGION OF
A POTENT NEGATIVELY TILTED SHORTWAVE TROUGH WILL LIFT NE INTO ERN SD
AS THE UPPER TROUGH EJECTS NEWD DURING THE EVENING. STRONG LOW LEVEL
CIRCULATION AROUND THIS SYSTEM IS TRANSPORTING MOISTURE FROM THE MS
VALLEY NW AND WWD INTO THE DAKOTAS WHERE IT IS UNDERGOING ISENTROPIC
ASCENT EAST OF MID LEVEL DEFORMATION AXIS THAT CURRENTLY EXTENDS N-S
THROUGH THE WRN DAKOTAS. OBJECTIVE ANALYSIS SHOWS AN AXIS OF
MODERATE FRONTOGENESIS ACROSS THE WRN DAKOTAS THAT WILL SHIFT NEWD
AS THE UPPER LOW EJECTS TOWARD THE UPPER MS VALLEY. THE
FRONTOGENETICAL FORCING MAY CONTRIBUTE TO AT LEAST MODEST STEEPENING
OF THE ISENTROPIC SURFACES AND TIGHTENING OF THE N-S MID LEVEL
THERMAL GRADIENT...WHICH WILL MAINTAIN A ZONE OF ENHANCED LIFT OVER
PARTS OF THE WRN DAKOTAS NEXT FEW HOURS. THIS LIFT WILL EXTEND
THROUGH LAYERS FAVORABLE FOR DENDRITIC SNOW GROWTH. FORECAST
SOUNDINGS ALSO SHOW A NEAR 100 MB DEEP ISOTHERMAL LAYER BETWEEN 800
AND 700 MB OVER WRN ND WHICH MAY ENHANCE SNOWFLAKE GROWTH THROUGH
THE AGGREGATION PROCESS.

..DIAL.. 02/09/2009

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

...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...ABR...BIS...UNR...

LAT...LON 48690020 47850047 46600099 45240142 44760229 45350303
46860365 48590320 48910210 48690020

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