SPC MD 2181

MD 2181 CONCERNING BLIZZARD FOR ERN NEB / W-CNTRL INTO NERN IA


MESOSCALE DISCUSSION 2181
NWS STORM PREDICTION CENTER NORMAN OK
0932 PM CST WED DEC 19 2012

AREAS AFFECTED...ERN NEB / W-CNTRL INTO NERN IA

CONCERNING...BLIZZARD

VALID 200332Z - 200900Z

SUMMARY...BLIZZARD CONDITIONS ARE BEGINNING OVER PARTS OF E-CNTRL
NEB AND WILL COMMENCE FROM WSW-ENE FROM NEAR THE MISSOURI RIVER
/04-06 UTC/ TO CNTRL IA /07-09 UTC/.

DISCUSSION...WATER VAPOR IMAGERY SHOWS A VIGOROUS UPPER TROUGH
MOVING EWD FROM THE CNTRL PLAINS TOWARDS THE LOWER MO RIVER VALLEY.
AS THIS OCCURS...00Z TOP RAOB SHOWED A MID LEVEL WARM NOSE AND THIS
EXTENDS INTO SRN IA/NRN MO EARLY THIS EVENING.  SURFACE MESOANALYSIS
SHOWS A DEEPENING 996 MB LOW OVER SERN KS THAT IS EXPECTED TO
DEVELOP ENEWD INTO W-CNTRL MO DURING THE OVERNIGHT.  A CONSISTENT
ENVELOPE OF WIND GUSTS AOA 35 MPH ENCOMPASSES E-CNTRL NEB SWWD INTO
THE WRN HALF OF KS...CREATING BLIZZARD CONDITIONS WHERE APPRECIABLE
SNOWFALL RATES/FRESHLY FALLEN SNOW ARE HINDERING VISIBILITIES.

MODEL GUIDANCE IS CONSISTENT IN SHOWING THE AXIS OF HEAVIEST
SNOWFALL RATES /1-1.5 INCH PER HR/ IN A SWATH NEAR THE MO RIVER AND
EVENTUALLY LATER OVER CNTRL AND NERN IA DURING THE 06-09 UTC PERIOD.
CONVECTIVE ENHANCEMENT TO PRECIP RATES OVER THE NEXT SEVERAL HOURS
IN IA /AS IMPLIED VIA OBSERVED LIGHTNING/ WILL ACT TO LOCALLY
AUGMENT RATES.  AS AN ASIDE...FORECAST SOUNDINGS SHOW THE COLUMN
COOLING 1-2 DEG C IN THE H8-H7 LAYER DURING THE 04-06 UTC TIME FRAME
NEAR DSM...TERMINATING MIXED P-TYPE /SNOW AND SLEET/ AND RESULTING
IN HEAVY SNOWFALL RATES.

MODEL DATA SHOW A TIME LAG ON THE ORDER OF SEVERAL HOURS FOR THE
HEAVIEST SNOWFALL RATES BEGINNING AND THE STRONGER WINDS
DEVELOPING...WHICH WILL LEAD TO INTERMITTENT BLIZZARD CONDITIONS
BECOMING MORE COMMON BY LATE TONIGHT.  TIMING OF BLIZZARD CONDITIONS
SEEMINGLY WILL OCCUR BY 06 UTC NEAR AND W OF THE MO RIVER...AND
APPROACH CNTRL IA BY 07-09 UTC.

..SMITH.. 12/20/2012

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

ATTN...WFO...DVN...ARX...DMX...EAX...OAX...

LAT...LON   43149231 43019179 42679168 42419180 41519341 40629567
            40309636 40309693 40529736 40979726 41429672 43149231

via SPC Forecast Products http://www.spc.noaa.gov/products/md/md2181.html