000 FXUS63 KILX 250000 AFDILX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 600 PM CST SUN FEB 24 2008 .DISCUSSION... ISSUED 125 PM CST SUN FEB 24 2008 SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT STORM SYSTEM FOR MONDAY NIGHT INTO TUESDAY THE MAIN SHORT TERM FORECAST CHALLENGE. WEAK WAVE/INVERTED TROF THAT PRODUCED SEVERAL INCHES OF SNOW ACRS THE I-70 CORRIDOR THIS MRNG HAS PUSHED OFF TO OUR EAST EARLY THIS AFTN WITH WEAK HIGH PRESSURE TAKING CONTROL. HOWEVER...THE WEAK SOUTHERLY FLOW HAS BROUGHT LOW LVL MOISTURE NWD INTO THE SRN HALF OF THE FCST AREA RESULTING AN INCREASE IN CLOUD COVER. THIS WEAK ADVECTION OF HIGHER DEW POINT AIR OVER WHAT IS LEFT OF THE SNOW COVER WL HELP PRODUCE SOME PATCHY FOG AGAIN OVERNIGHT ALONG WITH WARMER TEMPERATURES. SIGNIFICANT SHORTWAVE SEEN ON THE WATER VAPOR LOOP PUSHING INTO NRN CALIFORNIA WILL TRACK ACRS THE ROCKIES TNT AND REFORM OVER THE SRN PLAINS MONDAY AFTN. LOW PRESSURE WL DEVELOP ACRS KS IN RESPONSE TO THE APPROACHING UPPER LEVEL SYSTEM AND THEN TRACK EWD TO JUST NORTH OF ST LOUIS BY MIDNIGHT TUESDAY. SOUTHERLY WINDS AHEAD OF THE SYSTEM WILL DRAW UP WARMER AIR INTO CNTRL IL WITH MOST AREAS PUSHING INTO THE 40S...WITH LOWER 50S POSSIBLE EXTREME SOUTH. THE STRONG WARM ADVECTION PATTERN AHEAD OF THE SYSTEM MAY BE ENOUGH TO PRODUCE LOW CHANCE POPS ACRS OUR WEST DURING THE MORNING BUT THE BEST THREAT FOR RAIN WILL BE DURING THE AFTN AND EVENING HOURS WHEN THE STRONGER FORCING APPROACHES. THE GFS HAS BEEN RELATIVELY CONSISTENT WITH THE TRACK...AT LEAST COMPARED WITH THE NAM-WRF WHICH HAS BEEN TRACKING THE SFC LOW SOUTH WITH EACH RUN. LIKE THE IDEA OF A SLOWER EWD TRACK TO THE LOW AS THE UPPER LEVEL SYSTEM IS AMPLIFYING SOMEWHAT AS NRN STREAM ENERGY ENTERS FROM THE NW DURING THE DAY TUESDAY. SOUNDINGS INDICATING RAIN WILL CONTINUE INTO THE EVENING HOURS BEFORE CHANGING OVER TO POSSIBLY SOME HEAVY WET SNOW ACRS THE NORTH BY OR JUST AFTR MIDNIGHT TUE MRNG. RIGHT NOW IT APPEARS AREAS ALONG AND NORTH OF A LEXINGTON TO AVON HAVE THE POTENTIAL TO SEE SNOWFALL OF FROM 4 TO 6 INCHES WITH LESSER AMTS AS YOU HEAD SOUTH AS SOUNDINGS INDICATE THE CHANGEOVER TO SNOW WILL NOT OCCUR ALONG AND SOUTH OF I-74 UNTIL THE PREDAWN HOURS OF TUESDAY. BOTH MODELS INDICATE A DECENT TROWAL STRUCTURE /DEFORMATION ZONE ACRS THE AREA TUE MRNG. WILL ISSUE A WINTER STORM WATCH FOR THE ABOVE MENTIONED AREA FOR LATE MONDAY NIGHT THRU TUESDAY. THERE SHOULD EVEN BE ENOUGH ELEVATED INSTABILITY ACRS THE SOUTH TO SUPPORT A FEW THUNDERSTORMS AHEAD OF THE COLD FRONT AND NEAR THE H5 COLD CORE LATE MONDAY NIGHT INTO EARLY TUE MRNG. AS THE SYSTEM PULLS INTO INDIANA TUESDAY MRNG...STRONG NORTHERLY WINDS...GUSTING UP TO 40 MPH AT TIMES...WILL PRODUCE BLOWING AND DRIFTING OF THE SNOW THAT DOES ACCUMULATE...SO THE POTENTIAL IS INCREASING FOR A HIGH IMPACT EVENT LATE MONDAY NIGHT AND ESPECIALLY DURING THE DRIVE TO WORK OR SCHOOL TUESDAY MORNING. WITH THE TREND BEING FURTHER SOUTH...WE MAY HAVE TO ADJUST THE HEADLINES FURTHER SOUTH AS WELL...SO STAY TUNED. THE WEATHER CALMS DOWN A BIT ACRS CNTRL IL TUE NIGHT INTO WEDNESDAY AS THE STORM DEPARTS AND WINDS GRADUALLY DIMINISH. NWLY FLOW PATTERN WILL BE WELL ESTABLISHED ACRS THE REGION THRU MIDWEEK WITH COLDER THAN NORMAL TEMPS EXPECTED. WEAK SHORTWAVE NOTED ON BOTH THE GFS AND NAM-WRF TO PASS THRU ERN IOWA/WRN IL WED MRNG BUT WITH LIMITED MOISTURE TO WORK WITH...NOT MUCH IN THE WAY OF APPARENT WX OTHER FOR US. LONG TERM...THURSDAY THROUGH SUNDAY ACTIVE WEATHER PATTERN TO MAINTAIN ITSELF ACRS THE MIDWEST THIS PERIOD AS SHORTWAVE ENERGY RACES SE INTO THE MIDWEST LATE THU INTO FRIDAY BRINGING THE THREAT FOR LIGHT RAIN OR SNOW TO THE AREA. ONE FLY IN THE OINTMENT WILL BE WITH A SOUTHERN STREAM SHORTWAVE THAT MAY PLAY A PART IN THE WEATHER ACRS OUR SERN COUNTIES ON FRIDAY. AS THE POLAR FRONT...WHICH PUSHES ACRS MOST OF THE ILX AREA FRIDAY MRNG...STALLS OUT AHEAD OF THE SRN STREAM WAVE LATE FRIDAY...ADDITIONAL LIFT IS SENT NE ACRS THE LOWER OHIO VALLEY WHICH MAY KEEP RAIN CHANCES GOING A LITTLE LONGER IN OUR SOUTH. WL MAINTAIN THE HIGHER POPS ON FRIDAY ACRS THE SOUTH...CLOSER TO THE BOUNDARY AND UPPER LEVEL WAVE. THEN THE PATTERN TRANSITIONS TO A SOUTHWESTERLY FLOW AS STRONG PACIFIC ENERGY DIVES SE INTO THE SRN ROCKIES LATE IN THIS PERIOD RESULTING IN WARMER TEMPERATURES BUT UNFORTUNATELY...A VERY ACTIVE PRECIP PATTERN FOR US. TEMPS WHICH START OUT BELOW NORMAL BUT WILL CLIMB TO ABOVE NORMAL LEVELS BY THE END OF THE PERIOD WITH INCREASING CHANCES FOR SHOWERS AGAIN LATE SUNDAY OR MONDAY OF NEXT WEEK. SMITH && .AVIATION... ISSUED 600 PM CST SUN FEB 24 2008 TRICKY CEILING/VISIBILITY FORECAST THROUGH 00Z TAF PERIOD. WEAK HIGH PRESSURE IS OVER THE REGION...BUT LOW LEVEL MOISTURE REMAINS TRAPPED. MVFR CEILINGS/PATCHY FOG IS CURRENTLY OVER MOST OF THE TERMINALS AND EXTENDS WELL UPSTREAM. FORECAST MODELS HINT AT THE CLOUDS BREAKING UP FOR A TIME TONIGHT...BUT THIS WOULD LIKELY RESULT IN IFR FOG/STRATUS. FOR NOW...WILL KEEP CEILINGS/VISIBILITIES IN MVFR CATEGORY THROUGH MOST OF PERIOD. HAVE ALSO ADDED A CHANCE OF RAIN MONDAY AFTERNOON AHEAD OF AN APPROACHING STORM SYSTEM. BAK && .ILX WATCHES/WARNINGS/ADVISORIES... WINTER STORM WATCH FROM LATE MONDAY NIGHT THROUGH TUESDAY AFTERNOON FOR ILZ027>031. && $$