000 FXUS63 KILX 222111 AFDILX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 300 PM CST MON DEC 22 2003 .DISCUSSION... SHORT TERM...TONIGHT THROUGH WEDNESDAY... SURFACE FRONT HAS SAGGED INTO THE I-55 CORRIDOR AHEAD OF STRONG SHORTWAVE NOW MOVING INTO OKLAHOMA. RESULTING SURFACE WAVE WILL RIDE NORTHEAST ALONG THE FRONT AND THROUGH SOUTHERN ILLINOIS TOWARD DAWN. HEFTY NORTHERN STREAM SHORTWAVE MOVING SOUTHEAST THROUGH MINNESOTA WILL PHASE WITH THE SOUTHERN STREAM SYSTEM THROUGH 36 HOURS... RESULTING IN DEEPENING OF THE LOW PRESSURE TO OUR NORTHEAST. THE ETA AND GFS MODELS HAVE COME INTO REASONABLE AGREEMENT WITH THIS SCENERIO...SO THIS FORECAST PACKAGE WILL BE A BLEND OF THESE MODELS. ALTHOUGH THE GFS IS A LITTLE WETTER WITH THE QPF TONIGHT...THE ETA ALSO AGREES WITH A STRIPE OF AT LEAST MODERATE RAINFALL EXTENDING ACROSS THE SOUTHEASTERN COUNTIES. RICH LOW LEVEL MOISTURE ADVECTING NORTHWARD INTO THE SURFACE BOUNDARY WILL COMBINE WITH MARGINALLY STEEP MID LEVEL LAPSE RATES TO PRODUCE A FEW THUNDERSTORMS...SOME OF WHICH MAY MAKE IT UP INTO SOUTHERN ILLINOIS LATE TONIGHT. FURTHER NORTH...THE LIGHT RAIN WILL BEGIN TO CHANGE INTO SNOW AFTER MIDNIGHT AS COLDER AIR FILTERS INTO THE AREA. FORECAST SOUNDINGS FROM THE MESOETA WERE USED TO TRACK THE PROGRESSION OF THE CHANGE-OVER...REACHING CENTRAL ZONES TOWARD 12Z AND INTO THE SOUTHEAST DURING TUESDAY AFTERNOON. ANY MEANINGFUL SNOWFALL AMOUNTS ARE EXPECTED TO BE WELL NORTH OF THE AREA. ALTHOUGH THE DEEPEST FORCING WILL BE DEPARTING THE AREA TUESDAY AFTERNOON... WILL RETAIN SOME POPS FOR LIGHT SNOW/FLURRIES TUESDAY NIGHT AND WEDNESDAY UNTIL THE MAIN UPPER TROUGH AXIS MOVES THROUGH. LONG TERM...WEDNESDAY THROUGH MONDAY... MODIFIED PACIFIC AIR WILL OVERSPREAD THE REGION THURSDAY AND FRIDAY...WHICH POINTS TO A BRIEF COOLDOWN IN TEMPERATURES BEFORE A QUICK REBOUND TOWARD THE END OF THE WEEK. SOUTHERLY WINDS ARE EXPECTED TO ONCE AGAIN FIRM UP OVER THE AREA FRIDAY NIGHT THROUGH SATURDAY NIGHT...OPENING UP THE GULF AND BRINGING INCREASING MOISTURE AHEAD OF THE NEXT WAVE. MOS TEMPERATURES FROM THE MID 40S TO LOWER 50S LOOK REASONABLE FOR SATURDAY...WITH MILD TEMPERATURES CONTINUING INTO SATURDAY NIGHT AS THE SURFACE GRADIENT TIGHTENS UP AND CLOUDS BEGIN TO INCREASE. CHANCE POPS FOR RAIN STILL LOOK GOOD FOR SATURDAY NIGHT THROUGH SUNDAY AS THE NEXT FRONT MOVES THROUGH. PRESENT INDICATIONS ARE THAT THE PATTERN SHOULD BE PROGRESSIVE...SO WILL COUNT ON THE RAIN PUSHING EAST OF US BY DAY 7. && .ILX WATCHES/WARNINGS/ADVISORIES... IL...NONE. && $$ 04