SPC MD 2177

MD 2177 CONCERNING BLIZZARD FOR CNTRL/N-CNTRL/NERN KS…ERN NEB…CNTRL/WRN/SRN IA…NWRN MO


MESOSCALE DISCUSSION 2177
NWS STORM PREDICTION CENTER NORMAN OK
0208 PM CST WED DEC 19 2012

AREAS AFFECTED...CNTRL/N-CNTRL/NERN KS...ERN NEB...CNTRL/WRN/SRN
IA...NWRN MO

CONCERNING...BLIZZARD

VALID 192008Z - 200215Z

SUMMARY...BLIZZARD CONDITIONS WILL BEGIN DEVELOPING EWD/ENEWD ACROSS
THE AREA BY 23Z AND CONTINUE INTO TONIGHT.

DISCUSSION...RECENT WATER VAPOR AND IR SATELLITE LOOPS REVEAL A
VIGOROUS PV MAX EMERGING OVER THE CO HIGH PLAINS...WITH THE FIRST
INDICATIONS OF A COMPACT DEFORMATION ZONE EVOLVING FROM NERN CO INTO
NWRN KS AND SWRN NEB. THE SUPERPOSITION OF DEEP CONFLUENCE WITHIN
THIS DEFORMATION ZONE AND BACKGROUND BAROCLINICITY IS SUPPORTING
STRONG FRONTOGENESIS...WHICH IS YIELDING A HEAVY SNOW BAND
APPROXIMATELY 15-30 MILES EITHER SIDE OF A LINE FROM 30 SE AKRON CO
TO 35 NE MCCOOK NEB.

AS SFC CYCLOGENESIS CONTINUES OVER SWRN KS...WITH THE DEEPENING SFC
LOW TRACKING EWD AND EVENTUALLY NEWD IN TANDEM WITH THE MOTION OF
THE PV MAX...THE CORRESPONDING MASS RESPONSE WILL DRIVE AN EWD/ENEWD
SURGE OF THE ONGOING FRONTOGENESIS. CORRESPONDING ASCENT EXTENDING
THROUGH THE DENDRITIC GROWTH ZONE WILL ALLOW HEAVY SNOW WITH RATES
OF 1-1.5 IN/HR TO BEGIN DEVELOPING EWD/ENEWD ACROSS THE AREA BY
23Z...AND CONTINUE INTO TONIGHT. ALSO OF NOTE...AN ISOLATED
LIGHTNING STRIKE OR TWO MAY OCCUR WITHIN THE HEAVIEST SNOW BURSTS.
FURTHERMORE...FORECAST SOUNDINGS SUGGEST THAT RAIN/SLEET MAY
INITIALLY OCCUR BEFORE LOWER TROPOSPHERIC COOLING SUPPORTS A PHASE
CHANGE TO SNOW THIS EVENING FROM PARTS OF CNTRL/N-CNTRL/NERN KS NEWD
INTO S-CNTRL IA.

A VERY TIGHT SFC PRESSURE GRADIENT W/NW OF THE CENTER OF THE LOW
WILL SUPPORT NNWLY TO NELY WINDS OF 25 TO 40 MPH WITH GUSTS OF 45 TO
55 MPH. SUCH STRONG SPEEDS HAVE BEEN OBSERVED UPSTREAM. THESE WINDS
WILL BEGIN SPREADING EWD/ENEWD ACROSS THE DISCUSSION AREA BY 23Z.
SUPPORT FOR THESE WINDS WILL EMANATE FROM 40-50 KT OF 0-1-KM MEAN
FLOW PER FORECAST SOUNDINGS AMIDST STEEPENING SFC-1-KM-AGL LAPSE
RATES -- OWING TO AN EVENTUAL INCREASE IN COLD ADVECTION WITH
INCREASING HEIGHT JUST ABOVE THE SFC. THE COMBINATION OF THESE WINDS
AND SNOW/BLOWING SNOW WILL YIELD NEAR-ZERO VISIBILITIES AND BLIZZARD
CONDITIONS.

..COHEN.. 12/19/2012

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

ATTN...WFO...DVN...ARX...DMX...EAX...FSD...OAX...TOP...ICT...
GID...DDC...

LAT...LON   41499174 40899268 40619367 40369502 39509640 38349731
            38069836 38299895 39009868 39499829 40269750 40979760
            41589796 42399662 42989446 42939309 42669217 41999163
            41499174

via SPC Forecast Products http://www.spc.noaa.gov/products/md/md2177.html