SWOMCD
SPC MCD 201517
MNZ000-SDZ000-NDZ000-201945-
MESOSCALE DISCUSSION 0113
NWS STORM PREDICTION CENTER NORMAN OK
0917 AM CST SUN FEB 20 2011
AREAS AFFECTED...MUCH OF SD AND FAR SOUTHERN ND TO SOUTH-CENTRAL MN
CONCERNING...HEAVY SNOW
VALID 201517Z - 201945Z
HEAVY SNOWFALL WILL CONTINUE TO DEVELOP/INTENSIFY IN A GENERAL
WEST-EAST CORRIDOR ACROSS SD /MAINLY NORTH OF I-90/ AND EXTREME
SOUTHERN ND INTO SOUTH-CENTRAL MN INCLUDING THE TWIN CITIES.
LOCALIZED SNOWFALL RATES OF 1-2 IN/HR ARE LIKELY...ALONG WITH
BLIZZARD CONDITIONS AT TIMES ESPECIALLY ACROSS PORTIONS OF EASTERN
SD/SOUTHEAST ND AND SOUTHWEST MN.
AS A LEAD SHORTWAVE TROUGH CONTINUES TO PIVOT NORTHEASTWARD OVER THE
NORTHERN HIGH PLAINS...CONSIDERABLE DEEP FORCING FOR ASCENT OWING TO
DPVA...A COUPLED JET ALOFT...AND STRONG LOW LEVEL WARM
ADVECTION/ISENTROPIC LIFT WILL CONTRIBUTE TO A FAVORABLE SCENARIO
FOR HEAVY SNOWFALL WITH AN ARCTIC AIRMASS IN PLACE ACROSS THE
REGION. WITH SLANTWISE/SOME UPRIGHT CAPE AS EVIDENCED BY ONGOING
LIGHTNING THIS MORNING ACROSS FAR SOUTHERN MN/MUCH OF IA...AND STEEP
LAPSE RATES/WEAK ELEVATED BUOYANCY NOTED IN UPSTREAM OBSERVED RAOBS
SUCH AS 12Z RAPID CITY/NORTH PLATTE...PROXIMITY OF WEAK STATIC
STABILITY/STEEPENING LAPSE RATES ALOFT WILL CONTRIBUTE TO ENHANCED
SNOWFALL RATES WITH OTHERWISE FAVORABLE THERMODYNAMIC PROFILES FOR
AMPLE DENDRITIC/AGGREGATE SNOW GROWTH PER 12Z NAM/RUC FORECAST
SOUNDINGS. IN ADDITION...STRONG NORTHEASTERLY WINDS WILL CONTRIBUTE
TO BLIZZARD CONDITIONS AT TIMES...ESPECIALLY ACROSS EASTERN
SD/SOUTHEAST ND/SOUTHWEST MN TO THE EAST/NORTHEAST OF A DEVELOPING
INVERTED SURFACE TROUGH.
..GUYER.. 02/20/2011
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...MPX...FGF...FSD...ABR...BIS...UNR...
LAT...LON 45440348 46180202 46489752 46009324 45059293 44419385
44339762 43510071 44120282 45440348
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