Issued by NWS Central Illinois
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000 FXUS63 KILX 241115 AFDILX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 615 AM CDT FRI OCT 24 2008 .DISCUSSION... ISSUED 307 AM CDT FRI OCT 24 2008 MAIN PUSH OF PRECIP THROUGH THE AREA FOR NOW THIS MORNING...WARM AIR SURGING IN BEHIND THE PRECIP AND AHEAD OF THE MAIN SFC LOW. FORECAST ON TRACK SO FAR...MODELS ARE MOSTLY IN AGREEMENT FOR THE SHORT TERM...THOUGH SOME LINGERING THE PRECIP A BIT WITH RATHER COLD DRY AIR ON THE WAY LATER IN THE WEEKEND. WITH PREFERENCE TO NAM HANDLING OF MORE ARCTIC FRONTS...HAVE CHOSEN TO FOLLOW MOST CLOSELY WITH THE NAM. MAIN FORECAST ISSUES ARE THE EXIT OF THE PRECIP FROM THE APPROACHING LOW PRESSURE SYSTEM...WINDS ON SUNDAY...A BRUSH WITH ANOTHER SHORTWAVE DIGGING INTO THE TROF AS IT EXITS TO THE NE...AND NRN ILLINOIS GOING BELOW FREEZING TEMPS. BEYOND THE WEEKEND...THE FORECAST IS A BIT COLDER THAN MOS...AS GUIDANCE STILL PULLING THE TEMPS UP CONSIDERING SOME DEEP COLD AIR MOVING INTO PLACE LATE IN THE WEEKEND. SHORT TERM...TODAY AND TOMORROW... SHOWERY ACTIVITY LIKELY TO CONTINUE. MODELS KEEP CURRENT DRY SLOT IN PLACE OVER SW AND CENTRAL ILLINOIS FOR MUCH OF THE MORNING...UNTIL THE NEXT WAVE OF PRECIP DEVELOPS WITH A WEAK FRONTAL BOUNDARY MAKING ITS WAY AROUND THE LOW. THE WRAPPED UP LOW BECOMING MORE AMORPHOUS THROUGH THE NEXT 24 HOURS AS IT EXPANDS OVER THE REGION. SHOWERY ACTIVITY CONTINUING THROUGH TONIGHT...THEN ENDING SW TO NE AS A NEW TROF DIGS IN OVER THE NW...KICKING THIS LOW OUT TO THE NE. LONG TERM...SUNDAY THROUGH TUESDAY... MUCH COLDER TEMPS ON THE WAY BEHIND AN ARCTIC FRONT DROPPING THROUGH ON SUNDAY. THOUGH VERY LITTLE IN THE WAY OF PRECIP IS ANTICIPATED OVER MUCH OF THE AREA...WINDS WILL LIKELY BE AN ISSUE PREFRONT AND APPROACHING ADVSY CRITERIA IN THE NE. SINCE ACTUAL LOCATION OF THE HIGHEST WINDS IS A BIT OF A QUESTION MARK... SEE NO NEED TO BE THROWING OUT HEADLINES JUST YET. REMAINDER OF FCST A BIT LOWER THAN MOS AS MOS IS STILL CLINGING TO CLIMATOLOGY THAT IS A BIT TOO HIGH FOR THE ARCTIC BLAST ON THE WAY. WARMING BACK UP A BIT RELATIVELY SPEAKING ON TUESDAY. HJS && .AVIATION... ISSUED 615 AM CDT FRI OCT 24 2008 HIGHLY VARIABLE CLOUD CONDITIONS EXIST ACROSS CENTRAL IL AS BANDS OF MOISTURE ROTATE CYCLONICALLY AHEAD OF A DEEP VERTICALLY-STACKED LOW PRESSURE SYSTEM NOW OVER NWRN MO. 11Z CIGS RANGE FROM NONE TO LOWER THAN 1K FT AND EVERYTHING IN BETWEEN. PREDOMINATE CATEGORY THRU 15Z SHOULD BE MVFR THOUGH...AND WILL INDICATE THIS IN THE EARLY TAF ISSUANCE ALONG WITH A SCT-BKN LOWER DECK. CIGS WILL THEN SLOWLY RISE THRU THE DAY UNTIL A COLD FRONT ARRIVES IN THE 00Z-03Z SAT TIMEFRAME AND LOWERS THE CIGS AND SHIFTS THE WINDS TO WLY. PCPN-WISE...WE ARE CURRENTLY BETWEEN SHORTWAVES ROTATING AROUND THE SFC/UPR LOW WITH A CORRESPONDING LULL IN THE RAIN. ANOTHER WAVE IS SEEN MOVING NEWD THRU CENTRAL MO...AND THIS FEATURE WILL INDUCE AN UPSWING IN SHRA COVERAGE DOWNSTREAM OVR IL BY 18Z. WILL INDICATE A TEMPO FOR SHRA 19Z-22Z WITH THIS IN MIND...THEN HAVE A PREDOMINATE -RA WITH FRONTAL PASSAGE 22Z-02Z. AFTER THAT...MODEL DATA SUGGESTS DRYING IN THE LOWER LAYERS TAKING OVER...SO WILL CUT OFF THE PCPN FROM W TO E BUT KEEP BKN CIGS AROUND 3500 FT FOR THE REMAINDER OF THE TAF PD. 04 && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$
