585 FXUS63 KILX 041118 AFDILX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 518 AM CST SUN MAR 4 2012 .DISCUSSION... ISSUED 313 AM CST SUN MAR 4 2012 RIDGING OVER THE WESTERN HALF OF THE CONUS THIS MORNING AS AN UPPER TROF IS A LITTLE SLOW TO PROGRESS OUT OF THE MIDWEST...AND WILL REMAIN IN PLACE AS A CLIPPER SYSTEM PUSHES OUT OF THE CANADIAN ROCKIES DOWN INTO THE SYNOPTIC TROF TODAY AND TONIGHT BRINGING SNOW CHANCES FOR MUCH OF THE CWA...WITH THE HIGHER ACCUMULATIONS EXPECTED SOUTHWEST OF A LINE FROM PEORIA TO PARIS. MODELS ARE IN PRETTY GOOD AGREEMENT OVERALL THROUGH MIDWEEK. ISSUES IN THE FORECAST CROP UP IN THE EXTENDED WHEN ANOTHER TROF/LOW PRESSURE SYSTEM MOVE OUT OF THE ROCKIES AND SRN PLAINS...AND UP THE OHIO RIVER VALLEY. PREVIOUS MODEL RUNS HAVE HAD SOME SIGNIFICANT ISSUES DISCERNING THE BEHAVIOR ULTIMATELY OF THE UPPER LOW...WITH THE GFS MOST NOTABLY CLOSING OFF THE LOW AND STALLING A FRONTAL BOUNDARY FROM THE MID MISS RIVER VALLEY UP INTO THE APPALACHIANS. ECMWF WAS MORE PROGRESSIVE OVERALL IN PUSHING THE SYSTEM OUT QUICKLY. HOWEVER...THIS MODEL RUN BRINGS THE ECMWF IN LINE WITH A CLOSED OFF LOW OVER THE SRN HALF OF THE CONUS. NOT WILLING TO JUMP ON THE NEW RUN JUST YET...BUT WILL PRIME THE FORECAST FOR A FEW ADJUSTMENTS IN THE LATTER HALF OF THE WORK WEEK. SHORT TERM...TODAY AND TONIGHT... A QUICK CLIPPER SYSTEM IS PUSHING INTO THE MIDWEST THIS MORNING/AFTERNOON...BRINGING SNOW AFTER NOON AND THROUGH MIDNIGHT. PRECIP MAY START OUT AS RAIN IN THE EARLY AFTERNOON IN THE SWRN HALF OF THE STATE...BUT THERMAL PROFILES QUICKLY MOVE OVER TO ALL SNOW IN BOTH THE GFS AND THE NAM. 06Z HPC QPF PUTS THE FORECAST IN EXCESS OF THE 2 INCH RANGE...BUT WITH SOME RAIN EXPECTED EARLY AND A SLIGHT ADJUSTMENT TO THE QPF IN THE OVERNIGHT...BRINGS THE SNOW BACK TO A 1-2 INCH SCENARIO. TEMPS SIGNIFICANTLY COOLER NOW WITH THE SYSTEM OVERALL. ABOVE FREEZING TEMPS BRIEFLY STICK AROUND IN THE EARLY AFTERNOON HOURS PRIOR TO 22Z-00Z BEFORE EVAPORATIVE COOLING AND RATHER QUICK SATURATION OF THE COLUMN SHOULD HELP TO SWITCH MOST OF THE PRECIP OVER TO SNOWFALL. SNOW SHOULD BE WRAPPING UP JUST PRIOR TO MIDNIGHT AS THE CLIPPER MOVES OUT INTO THE LARGER SCALE TROF AND EXITS THE REGION. LONG TERM...TOMORROW THROUGH SATURDAY... WARMING TREND DELAYED A BIT MONDAY...WITH HIGH PRESSURE BUILDING INTO THE MIDWEST AND ERN HALF OF THE CONUS. HOWEVER...TUES AND WED LIKELY TO SEE TEMPS AROUND AND ABOVE 60 WITH PLENTY OF SOUTHERLY WINDS AND LLVL WAA KICKING IN IN THE OVERNIGHT HOURS MON NIGHT. WINDY CONDITIONS PREVAIL FOR TUESDAY AS THE MIDWEST GETS CAUGHT BETWEEN A STUBBORN RIDGE OVER THE ATLANTIC STATES AND ANOTHER VIGOROUS WAVE DIGGING IN OVER THE ROCKIES. AN ADVANCING COLD FRONT BRINGS PRECIP TO THE REGION WITH THE INITIAL LARGE TROF. PRECIP...RAIN OR SNOW...WED NIGHT THROUGH THURSDAY NIGHT. KEEPING FRIDAY POPS AWAY STILL...BECAUSE THE MODELS HAVE PREVIOUSLY BEEN IN CONFLICT OVER ONE POINT. THE GFS CUTS OFF THE 500 MB LOW...PUSHING A WARM FRONTAL FEATURE INTO THE OHIO RIVER VALLEY ON FRIDAY. HOWEVER...THE MORE PROGRESSIVE ECMWF HAS BEEN EXITING THE SYSTEM ALTOGETHER...NEVER FORMING THE CUT OFF 500 MB LOW. HOWEVER...THE 00Z RUN SEEMS TO BE GOING THE WAY OF THE GFS. NEXT ISSUE WILL BE A MATTER OF HOW FAR NORTH ANY WARM FRONT ACTUALLY SETS UP WITH A LINGERING CUT OFF LOW IN THE SW. HJS && .AVIATION... ISSUED 518 AM CST SUN MAR 4 2012 ALBERTA CLIPPER SYSTEM WILL MOVE SOUTHEASTWARD THROUGH THE MIDWEST LATER TODAY...WITH THE CENTER OF THE SURFACE LOW TAKING A TRACK FROM THE DAKOTAS TO SOUTHEASTERN MO TO SOUTHERN KY. BAND OF SNOW TO THE LEFT OF THE TRACK WILL AFFECT SPI THE STRONGEST WITH MVFR TEMPO IFR CONDITIONS...WITH OTHER SITES FURTHER NORTH/EAST GETTING A MORE GLANCING BLOW WITH MAILY MVFR. WILL START THE SNOW AT PIA/SPI AROUND 22Z...AND A LITTLE LATER FOR BMI/DEC/CMI. THE SNOW WILL BE MOVING PAST THE TERMINALS BY 06Z...LEAVING BEHIND SOME MVFR STRATOCU WHICH WILL THEN CLEAR FROM WEST TO EAST AFTER 06Z. WINDS WILL BE WESTERLY AROUND 10 KT BEFORE THE SNOW ARRIVES...LIGHT NORTHERLY AS THE LOW MAKES ITS PASS TO THE WEST LATE AFTERNOON/EVENING...THEN NORTHWEST 10-15 KT AFTER 06Z. 04 && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$