MESOSCALE DISCUSSION 2564
   NWS STORM PREDICTION CENTER NORMAN OK
   1212 PM CST WED DEC 22 2004
   
   AREAS AFFECTED...SERN OK...CENTRAL/NRN AR...FAR SERN MO...FAR SRN
   IL...FAR WRN KY...WRN/NWRN TN
   
   CONCERNING...WINTER MIXED PRECIPITATION 
   
   VALID 221812Z - 222215Z
   
   HEAVY SNOW WILL DEVELOP NEWD FROM SERN OK INTO N-CENTRAL/NRN AR
   ...FAR SERN MO...FAR SRN IL...AND WRN KY THIS AFTERNOON INTO EARLY
   THIS EVENING. FREEZING RAIN AND SLEET IS LIKELY MUCH OF THIS
   AFTERNOON FROM CENTRAL AR ENEWD INTO SWRN TN. 
   
   AT 1730Z...ELONGATED FRONTAL ZONE EXTENDED FROM PARENT CYCLONE OVER
   WRN QUEBEC SWWD ACROSS THE OH/TN VALLEYS TO A SECONDARY LOW NEAR THE
   TX UPPER COAST. THIS LOW WILL TRACK NEWD TO SWRN MS BY 00Z...WITH
   CONTINUED ADVECTION OF DRY POLAR LOW-LEVEL AIR ACROSS THE SRN PLAINS
   EWD INTO THE MID-MS RIVER VALLEY. 
   
   IMPRESSIVE 500MB TROUGH AND ASSOCIATED 80KT JET MAX WILL ROTATE EWD
   ACROSS NRN/CENTRAL TX THROUGH 00Z. COUPLED 300MB JET STRUCTURE
   BECOMES WELL ESTABLISHED ACROSS AR NEXT SEVERAL HOURS...AS DOES
   MID-LEVEL PVA LEADING TO DEEP LAYER VERTICAL MOTION FROM SERN OK
   NEWD ACROSS CENTRAL/NRN AR INTO THE LOWER OH RIVER VALLEY BY EARLY
   TONIGHT. IN ADDITION...SYSTEM IS TAPPING AMPLE GULF MOISTURE AND
   MARGINAL INSTABILITY LEADING TO IMPRESSIVE PRECIPITATION SHIELD THAT
   SHOULD EXPAND NWD OVER SUBFREEZING AIR ACROSS NRN AR EWD TO WRN KY
   DURING NEXT 6 HOURS. FRONTOGENETIC FORCING IS PROGGED TO BECOME
   BETTER ESTABLISHED NEWD FROM UPPER TROUGH ACROSS NRN AR INTO FAR
   SERN MO AND NWRN TN/WRN KY LEADING TO REDEVELOPMENT OF MODERATE TO
   HEAVY SNOW ACROSS ERN PORTIONS OF THIS AXIS LATE THIS AFTERNOON INTO
   EARLY EVENING. SNOW RATES OF 1"/HR APPEAR LIKELY ACROSS THIS REGION
   FOR AT LEAST SEVERAL HOURS. 
   
   STRENGTHENING ISENTROPIC ASCENT ACROSS CENTRAL AR INTO WRN TN SHOULD
   RESULT IN FAVORABLE PROFILES FOR FREEZING RAIN OR SLEET THIS
   AFTERNOON FROM LIT EWD TO MEM AND ADJACENT AREAS JUST TO THE NORTH.
   18Z SOUNDING FROM LIT INDICATES ABOVE FREEZING LAYER FROM 850-750MB.
   SHALLOW NEAR-SURFACE COLD ADVECTION IS LIKELY...HOWEVER...COOLING
   ALOFT IS UNLIKELY UNTIL MID-LEVEL TROUGH MOVES OVERHEAD EARLY THIS
   EVENING. 
   
   RUC SOUNDINGS THIS AFTERNOON INDICATE ELEVATED INSTABILITY WHICH
   SHOULD RESULT IN HEAVY FREEZING RAIN/SLEET AND POSSIBLE
   THUNDERSTORMS. DESPITE INTENSE PRECIPITATION RATES...MARGINAL GROUND
   TEMPERATURES MAY LIMIT EXTENT OF SURFACE ICING ALTHOUGH SOME THREAT
   SHOULD EXIST ON ELEVATED ROADS AND STRUCTURES.
   
   ..BANACOS.. 12/22/2004
   
   
   ...NOTICE...
   SPC WINTER WEATHER MESOSCALE DISCUSSIONS WILL BE ISSUED ON A 
   SCHEDULED BASIS...FOUR TIMES A DAY...BETWEEN 00-01 UTC...
   06-07 UTC...12-13 UTC...AND 18-19 UTC AS SIGNIFICANT SHORT
   RANGE WINTER WEATHER EVENTS UNFOLD.  THIS SCHEDULE WILL BE
   USED FROM DECEMBER 1 THROUGH FEBRUARY 28.
   
   ATTN...WFO...OHX...PAH...MEG...LZK...SGF...SHV...TSA...
   
   35979293 36958989 37478839 37168766 36438772 36188778
   35508897 35048992 34729061 34349176 34159374 33919477
   33899515 34079537 34549530 35349432 35939295