MESOSCALE DISCUSSION 0077
   NWS STORM PREDICTION CENTER NORMAN OK
   0640 AM CST WED JAN 17 2007
   
   AREAS AFFECTED...CNTRL AND ERN TX
   
   CONCERNING...FREEZING RAIN 
   
   VALID 171240Z - 171645Z
   
   FREEZING RAIN AND SLEET WILL CONTINUE ACROSS CNTRL AND EAST TX
   THROUGH EARLY AFTERNOON. UP TO A QUARTER INCH OF ADDITIONAL ICE
   ACCUMULATION WILL BE POSSIBLE.
   
   LATEST SFC ANALYSIS SHOWS A RIDGE OF ARCTIC HIGH PRESSURE EXTENDING
   SWWD FROM THE MID MS VALLEY INTO THE SRN PLAINS. IN RESPONSE TO THE
   SFC HIGH...WINDS ACROSS CNTRL AND EAST TX ARE NLY WITH SUBFREEZING
   TEMPS EXTENDING SWD TO THE GULF COAST AND INTO FAR SOUTH TX. THE 12Z
   SOUNDINGS FROM VICTORIA TX AND LAKE CHARLES LA SHOW A RELATIVELY
   THICK WARM LAYER EXISTS FROM AROUND 850 MB TO ABOVE 700 MB. COMPLETE
   MELTING OF PRECIPITATION IN THIS WARM LAYER WILL RESULT IN FREEZING
   RAIN AT THE SFC. HOWEVER...SLEET MIXED WITH LIGHT SNOW WILL STILL BE
   POSSIBLE ACROSS THE NRN PART OF THE MCD AREA WHERE THE SUB-FREEZING
   LAYER AT THE GROUND IS DEEPER. ACROSS NRN TX...A TRANSITION TO SNOW
   SHOULD GRADUALLY OCCUR.
   
   CONCERNING PRECIPITATION COVERAGE...RADAR AND SFC OBSERVATIONS
   CURRENTLY SHOW MULTIPLE AREAS OF FREEZING RAIN EXTENDING FROM NEAR
   DEL RIO TX EWD ACROSS THE SAN ANTONIO/AUSTIN TX AREA TO THE LA
   STATE-LINE. THIS IS ASSOCIATED WITH A SUBTROPICAL PLUME OF MID-LEVEL
   MOISTURE AND AN 80 KT MID-LEVEL JET IN NRN MEXICO. AS THE MID-LEVEL
   JET EJECTS ENEWD INTO THE TX HILL COUNTRY THIS MORNING...LARGE-SCALE
   ASCENT ASSOCIATED WITH THE EXIT REGION WILL ENHANCE PRECIPITATION IN
   AREAS FROM SAN ANTONIO TX EWD TO THE TX-LA STATE-LINE. QPF AMOUNTS
   SHOULD RANGE FROM A TENTH TO A QUARTER INCH WITH THE SIGNIFICANT ICE
   ACCUMULATION ESPECIALLY ACROSS EAST TX.
   
   ..BROYLES.. 01/17/2007
   
   
   ...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...LCH...SHV...HGX...FWD...EWX...SJT...
   
   29859435 29499671 29019942 29229999 29920040 30620019
   31119823 31409649 31619488 31589405 30869369 30079384