902 FXUS63 KLOT 040008 AFDCHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHICAGO IL 610 PM CST MON MAR 3 2003 AVIATION DISCUSSION FOR 00Z TAFS... PASSING SHORT WAVE ACROSS SRN WI/NRN IL MORE THAN HALFWAY THRU TERMINALS. ABOUT 3 HOURS LEFT OF SNOW BEFORE TAPERING OFF IN NERN IL. CIGS GENERALLY LOW MVFR AND VSBY IFR WITH CIGS OCNLY AT IFR AS WELL. EXPECT AFT 03-04Z CIGS AND VSBY TO RISE TO MVFR. VSBY MAY RISE TO VFR AFT MDNGT BUT NOT MUCH HOPE FOR VFR CIGS UNTIL NEAR DAYBREAK...AND THIS ONLY BRIEFLY IN THE MORNING AS NEXT PATTERN OF OVERRUNNING MOISTURE FROM THE GULF TO BRING ANOTHER BOUT OF SNOW. PRESENT SHORT WAVE TRAILING A COLD FRONT SW THRU CENTRAL IOWA. THIS COLD FRONT MOVING THRU NRN IL TUES MRNG AND INTO NWRN IN BY ERY AFTN. THEN FNT GOES STNRY AS STRONG LOW IN SRN PLAINS DEEPENS AND SHOOTS OVERRUNNING MSTR OVER THIS FNTL BNDRY INTO NRN IL/NWRN IN. SNOW LIKELY TO BEGIN AGAIN IN THE ERY AFTN WITH CIGS STARTING TO DROP TO IFR AGAIN AND SNOW INTENSIFYING THRU LATE AFTN AND TUESDAY EVENING. SNOWFALL LIKELY TO BE SIGNIFICANT ALONG AND SOUTH OF I-80 WITH LESSER AMOUNTS TAPERING TOWARD THE WISCONSIN BORDER. WINDS SOUTH 10-20 KTS TNGT AND GRADUALLY TRYING TO VEER NORTHWEST MID TO LT TUESDAY MORNING. RLB PUBLIC DISCUSSION FOR 4 PM PUBLIC FORECAST... AREA OF LIGHT SNOW WILL COMPLETE ITS PASS ACROSS THE CWA THIS EVENING. SNOWFALL AMOUNTS CONTINUE TO BE EXPECTED TO BE SLIGHT AND GENERALLY LESS THAN AN INCH. TODAY/S SNOW IS OF MINOR CONCERN METEOROLOGICALLY COMPARED WITH POTENTIAL FOR SIG SNOW TUESDAY NIGHT. AFTER SEVERAL RUNS WITH DIFFERENCES MODELS APPEAR TO BE CONVERGING ON A SIMILAR SOLUTION. BY 12Z TUESDAY SURFACE LOW DEVELOPS ON SOUTHERN PLAINS WHILE SURFACE LOW ASSOCIATED WITH TODAY/S SNOW IS POSITIONED NEAR THE SOO. SOUTHERN LOW DEEPENS AND BECOMES ELONGATED IN PRESSURE TROUGH EXTENDING TO THE NORTHEAST. GOOD BAROCLINIC ZONE IS ESTABLISHED WITH UVV ASSOICATED WITH SURFACE LOW DEVELOPMENT POISTIONED AT WESTERN EDGE OF FORECAST AREA. COLUMN APPEARS SATURATED BY 06Z WHEN MAX UVV PASSES ACROSS AREA. QPF TOTALS VARY FROM MODEL TO MODEL AND RANGE FROM ABOUT 1/3 INCH TO OVER 1. LINKED SNOWFALL TOTALS VARY OVER THAT SAME RANGE BUT APPEAR TO BE AT LEAST IN THE 3 TO 6 INCH RANGE. FINAL TOTALS AND PLACEMENT MAY WELL TAKE ANOTHER MODEL RUN TO DEFINE MORE DEFINITVELY. POTENTIAL DOES EXIST HOWEVER FOR SEVERAL INCHES MORE THAN THE UPPER LIMIT MENTIONED. IN THE MEANTIME SETUP WARRANTS A WINTER STORM WATCH FOR TUESDAY NIGHT. SNOW WILL END EARLY WEDNESDAY AS LARGE SURFACE HIGH SETTLES OVER MIDWEST. AS IN PREVIOUS MODEL RUNS UPPER FLOW BECOMES WEST NORTHWESTERLY WITH SHORT WAVES GENERALLY STAYING TO THE NORTH. FLOW PATTER ALLOWS MODERATION IN TEMPS THOUGH SIG SNOW ON THE GROUND MAY WELL HOLD MAXS BELOW GUIDANCE NUMBERS. FLOW SHARPENS UP BY SATURDAY WITH SHORT WAVES DIGGING SOUTHEAST FROM CANADA. THIS SYSTEM SHOULD FORCE WX TO MOVE FAR ENOUGH SOUTH TO IMPACT FORECAST AREA. .CHI...WINTER STORM WATCH TUESDAY NIGHT ENTIRE FORECAST AREA FREEZING SPRAY WARNING TONIGHT LAKE MICHIGAN SOMREK