MESOSCALE DISCUSSION 2559 NWS STORM PREDICTION CENTER NORMAN OK 0104 AM CST WED DEC 22 2004 AREAS AFFECTED...SERN MO/NRN AR...SRN IL/IND...FAR NRN/WRN KY AND SERN OH CONCERNING...PRECIPITATION TRENDS...WINTER PRECIPITATION VALID 220704Z - 221300Z A MIX OF FREEZING RAIN AND SNOW WILL CONTINUE TO DEVELOP OVER THE REGION THROUGH 12Z...WITH THE HEAVIEST SNOW /HRLY RATES UP TO 1 INCH/ ANTICIPATED ALONG A 30 MILE WIDE AXIS CENTERED FROM UNO TO BMG THROUGH 13Z. FARTHER SOUTH...THE RAIN SHOULD GRADUALLY CHANGE TO FREEZING RAIN ACROSS THE OHIO VALLEY OF SERN OH..NRN/WRN KY SWWD INTO NERN AR. LATEST TRENDS IN IR IMAGERY INDICATES UPPER LEVEL DYNAMICS WERE INCREASING OVER THE REGION AS A STRONG UPPER TROUGH MOVES OUT OF THE SRN ROCKIES. STRONGEST FRONTOGENETIC FORCING WILL CONTINUE TO ORIENT ITSELF ALONG THE MID LEVEL FRONTAL ZONE/UPPER JET AXIS FROM NRN AR INTO SRN IND OVER THE NEXT 6 HOURS SUPPORTING INCREASING SNOWFALL RATES. LOW LEVEL CAA AND SATURATION WILL CONTINUE TO AID IN SWD MOTION OF SFC WET BULB FREEZING LINE TO A LITTLE ROCK TO CINCINNATI LINE BY 13Z. HOWEVER...AS THE LOW LEVEL CAA SUPPORTS THE SWD MOVEMENT OF THE SFC FREEZING LINE...MOD-STRONG WAA IN THE 850-925 MB LAYER WILL CONTINUE TO LIMIT THE SWD MOTION OF THIS LAYER/S FREEZING ISOTHERM AXIS OVER THE OHIO VALLEY. THUS...A NARROW ZONE...LESS THAN 50 MILES WIDE OF FREEZING RAIN AS THE PREDOMINANT PTYPE IS ANTICIPATED TO DEVELOP SWD AND EXTEND FROM NERN AR INTO FAR WRN/NRN KY AND SERN OH BY 13Z. ..CROSBIE.. 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...ILN...LMK...IND...PAH...ILX...MEG...LSX...LZK...SGF... 38728382 37918554 37548635 36688857 36288925 35659023 35229172 35619308 36349256 37599043 38418922 39168737 39468473