778 FXUS63 KILX 290314 AFDILX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 914 PM CST FRI DEC 28 2012 .DISCUSSION... ISSUED 904 PM CST FRI DEC 28 2012 STRONG DYNAMICS OVER THE SOUTHEAST WITH APPROACHING WINTER STORM PUSHING HIGHER SNOW TOTALS INTO SOUTHERN ILLINOIS...PARTICULARLY SOUTH OF INTERSTATE 70. FRONTOGENETIC FORCING BULLSEYE OVER THE BAND SETTING UP OVER THE LAST THREE HOURS FROM CLAY COUNTY TO CRAWFORD...AND SLOWLY THE BAND IS DRIFTING SE. UPDATED THE GRIDS WITH THE EXPANSION OF THE WINTER WEATHER ADVISORY FOR HIGHER SNOW TOTALS. ZONES AND UPDATED GRIDS ALREADY OUT. CONCERN FOR REDUCED VIS AND FZDZ POTENTIAL IN THE OVERNIGHT...THOUGH MAJORITY OF THAT HAS BEEN REPORTED NORTH OF ILX CWA...AND VIS AND TEMPS HOLDING. HJS && .AVIATION... ISSUED 548 PM CST FRI DEC 28 2012 NOT MUCH OF A SHIFT IN THE FORECAST. MAJORITY OF SNOW TO THE SE THIS EVENING AND AWAY FROM TAF SITES. HOWEVER...SOME SNOW SHOWERS REMAIN POSSIBLE THROUGH THE OVERNIGHT AND INTO THE EARLY MORNING...WITH BEST CHANCES FOR REDUCED VIS IN SPI DEC AND CMI. MOSTLY MVFR CIGS FOR NOW...WITH IFR LIKELY AS THE SNOW SHOWERS PUSH IN FROM THE SOUTH AND THE SYSTEM MOVES CLOSER. VARIABLE WINDS BECOMING MORE NORTHWESTERLY...AND KEEPING THE LOW STRATUS IN THROUGH THE TAF PD. TIME HEIGHTS ARE BEGINNING TO HINT THAT LLVL RH THINS A BIT JUST BEFORE 00Z TOMORROW...BUT WILL NOT ADJUST FORECAST UNTIL MORE PROOF IS PRESENTED. HJS && .PREV DISCUSSION... ISSUED 300 PM CST FRI DEC 28 2012 A COUPLE OF WEATHER SYSTEMS WILL HIGHLIGHT THE FORECAST FOR THE NEXT WEEK...ALONG WITH TEMPERATURES REMAINING AT OR BELOW NORMAL. THE FIRST STORM WILL BE TONIGHT...AND THE SECOND WILL COME ON NEW YEARS EVE DAY AND OVERNIGHT. SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT. THE FIRST SYSTEM IS ALREADY PUSHING INTO OUR SOUTHEASTERN COUNTIES...WHERE A WINTER WEATHER ADVISORY FOR 2-3 INCHES OF SNOW HAS BEEN ISSUED FOR TONIGHT. WE INCLUDED 6 OF OUR SOUTHEAST COUNTIES...FROM EFFINGHAM TO THE SOUTH AND EAST. HEAVIER SNOW OF 3 TO 6 INCHES WILL BE POSSIBLE SOUTHEAST OF OUR COUNTIES...IN SOUTHERN INDIANA, NW KENTUCKY, AND SOUTHERN ILLINOIS. THE BULK OF THE SNOW IN OUR AREA WILL FALL THIS EVENING. TRAVEL WILL QUICKLY BECOME HAZARDOUS BY EARLY EVENING AS ROADS BECOME SNOW COVERED AND SLIPPERY. THE NORTHERN EDGE OF MEASURABLE SNOW MAY REACH AS FAR NW AS TAYLORVILLE TO DECATUR TO CHAMPAIGN...BUT ONLY A DUSTING SHOULD REACH THAT FAR TO THE NW. SOUTH WINDS AS THE SNOW BEGINS WILL SHIFT TO NORTHWEST AS THE LOW PRESSURE MOVES AWAY TO THE SOUTHEAST AFTER MIDNIGHT. WINDS SHOULD NOT BE ALL THAT STRONG DURING THIS SNOW EVENT...WHICH SHOULD KEEP DRIFTING DOWN. ON SATURDAY...A SHORTWAVE AND THE CENTER OF THE COLD POOL IN THE UPPER LEVEL TROUGH WILL MOVE ACROSS ILLINOIS. THAT WILL SET THE STAGE FOR SCATTERED FLURRIES ACROSS OUR FORECAST AREA. NO MEASURABLE SNOW IS EXPECTED...AS THE FLURRIES TAPER OFF LATER IN THE AFTERNOON. CLEARING SKIES SHOULD DEVELOP SATURDAY NIGHT...AS COLD HIGH PRESSURE ADVANCES INTO THE AREA FROM WEST TO EAST. LOW TEMPS WILL BE CLOSELY TIED TO THE TIMING OF THE CLEARING. WE ARE PLANNING ON HAVING FAVORABLE RADIATIONAL COOLING FOR MUCH OF THE NIGHT IN THE WEST...WHERE WE WENT WITH SOME SINGLE DIGIT LOWS TOWARD GALESBURG AND ALTONA. SOUTHEASTERN AREAS MAY EVEN SEE LOWS AROUND 15F. SUNDAY SHOULD BE MOSTLY SUNNY WITH SOUTHERLY WINDS DEVELOPING BEHIND THE DEPARTING HIGH PRESSURE. SOME WARMING ALOFT MAY SHOULD HELP TEMPS CLIMB TO AROUND FREEZING ACROSS THE SOUTHWEST. CLOUDS ARRIVING SUNDAY NIGHT WILL HELP KEEP LOWS IN THE MID 20S AHEAD OF THE NEXT STORM SYSTEM. LONG TERM...MONDAY THROUGH FRIDAY. A COUPLE OF WEATHER FEATURES ARE EXPECTED TO MERGE ACROSS ILLINOIS TO PRODUCE A LIGHT SNOW EVENT NEW YEARS EVE DAY AND OVERNIGHT. A LOW LEVEL COLD FRONT ARRIVING FROM THE NORTHWEST WILL INTERACT WITH A 500 MB VORT MAX AND A 170KT 300MB JET TO GENERATE A BAND OF SNOW ACROSS CENTRAL ILLINOIS. THE SNOW BAND IS FORECAST TO OVERSPREAD THE AREA FROM SOUTHWEST TO EAST-NORTHEAST STARTING MONDAY MORNING. NEW YEARS EVE NIGHT...A SECOND SURGE OF 500MB ENERGY AND AN INTENSIFICATION OF THE 300MB JET TO 185KT WILL KEEP SNOW SHOWERS GOING FOR MUCH OF THE NIGHT AS WELL. SNOW WILL TAPER OFF AFTER MIDNIGHT...AS THE COLD FRONT DEPARTS FARTHER TO THE EAST AND ISENTROPIC DOWNGLIDE BEGINS TO DOMINATE THE SYNOPTIC FORCING. SNOWFALL AMOUNTS ARE A TOUGH CALL THIS EARLY...BUT 2-4 INCHES WILL BE POSSIBLE IN THE SOUTHERN HALF OF OUR AREA...SOUTH OF A LINE FROM RUSHVILLE TO LINCOLN TO CHAMPAIGN. THE LOWER TOTALS WILL BE IN THE NORTH...WITH HIGHER AMOUNTS BETWEEN I-72 AND I-70. WARMER AIR ALOFT MAY REDUCE SNOW AMOUNTS SOUTH OF I-70...BUT STILL IN THE 2-3 INCH RANGE. GENERALLY DRY AND COOL CONDITIONS ARE EXPECTED FROM NEW YEARS DAY THROUGH FRIDAY...AS SURFACE HIGH PRESSURE REMAINS THE MAIN PRESSURE FEATURE. A WEAK COLD FRONT AND 500MB SHORTWAVE IS FORECAST TO PASS ACROSS IL ON THURSDAY...SO SOME FLURRIES MAY DEVELOP THAT DAY...BUT WE WILL CONTINUE WITH A DRY FORECAST FOR NOW. && .ILX WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 6 AM CST SATURDAY FOR ILZ062-063- 066>068-071>073. && $$