FXUS63 KLSX 210518 AFDLSX AREA FORECAST DISCUSSION...UPDATED AVIATION NATIONAL WEATHER SERVICE ST LOUIS MO 1218 AM CDT SUN MAR 21 2010 .UPDATE... /905 PM CDT SAT MAR 20 2010/ FORECAST IN GOOD SHAPE AS WARM AIR ALOFT ALREADY MIXING SNOW WITH SLEET AND RA/FZRA ACROSS CENTRAL MISSOURI. FORCING AND FOCUS OF PRECIPITATION WILL SHIFT FROM NORTHWESTERN CWA TO SOUTHERN CWA OVERNIGHT AS ENTIRE STORM SYSTEM DEEPENS TO OUR SOUTH. LATEST RUC PROGS 850 TEMPERATURES TO BE 2 TO 6 DEGREES ABOVE ZERO ACROSS THE ENTIRE CWA BY 12Z. IF THIS PANS OUT...THE ADVISORIES MAY BE DROPPED EARLY AS PRECIPITATION TURNS TO ALL RAIN. CVKING && .DISCUSSION... /318 PM CDT SAT MAR 20 2010/ PLAN ON LEAVING GOING ADVISORY AS IS FOR THIS FORECAST. MODELS REMAIN IN RELATIVELY GOOD AGREEMENT THAT CLOSED CURRENTLY OVER THE SRN PLAINS WILL MOVE SLOWLY EWD INTO THE LOWER MISSISSIPPI RIVER VALLEY ON SUNDAY BEFORE LIFTING NEWD IN THE MID ATLANTIC. RAIN/SNOW OVER THE NWRN HALF OF THE CWA CURRENTLY IS BEING GENERATED BY DECENT 800-600MB FRONTOGENESIS WHICH IS PROGGED TO GRADUALLY DIMINISH THROUGH THE NIGHT. BY SUNDAY MORNING...GREATEST LIKELIHOOD OF PRECIPITATION WILL SHIFT TO THE SRN CWA WHERE MID LEVEL FRONTOGENESIS/LOW-MID LEVEL MOISTURE CONVERGENCE WILL MARKEDLY INCREASE. FORCING IN THE NRN PART OF THE CWA WILL DECREASE BRINGING ONLY SLGT CHC/CHC POPS FOR THE WINTRY MIX. FOCUS FOR PRECIP WILL THEN GRADUALLY SHIFT INTO THE SERN CWA BY LATE SUNDAY/EARLY MONDAY AS UPPER LOW LIFTS OUT. THIS INTENSE SYSTEM WILL CONTINUE TO WRAP WARM AIR AROUND IT...WITH FORECAST SOUNDINGS FROM BOTH THE NAM/GFS INDICATING THAT THERMAL PROFILES IN THE AREA CURRENTLY SEEING SNOW WILL CLIMB ABOVE +1C IN THE 950-850MB LEVEL...AND EVENTUALLY ABOVE +3C BY MIDNIGHT WHICH FAVORS SNOW CHANGING TO SLEET AND THEN RAIN OR FREEZING RAIN LATE TONIGHT/EARLY SUNDAY DEPENDING OF SURFACE TEMPERATURE. THE HEAVIEST AXIS OF ADDITIONAL SNOW/SLEET OF UP TO 2" WILL LIE NORTHWEST OF A COU-UIN LINE TONIGHT. HAVE INCLUDED THE MENTION OF -FZRA OVER CNTRL/NERN MO AND W CNTRL IL LATE TONIGHT/EARLY SUNDAY MORNING AS LOWER ATMOSPHERE CONTINUES TO WARM...BUT DO NOT EXPECT MUCH ICE ACCUMULATION. PRECIPITATION AXIS WILL BE SHIFTING SWD AND GROUND TEMPS ACCORDING TO MO AG WX OBS ARE IN THE MID 30S TO AROUND 40. DID BACK OFF ON HIGH TEMPERATURES A BIT THE NEXT TWO DAYS BASED ON CLOUDS AND PRECIPITATION. MAIN QUESTION FOR THE EXTENDED PART OF THE FORECAST IS TIMING AND AREAL EXTEND OF PRECIPITATION WITH NEXT CLOSED LOW MOVING INTO THE CNTRL CONUS LATE NEXT WEEK. WHILE THE GFS/GEM/ECMWF ARE SHOWING SOME MINOR CONTINUITY ISSUES AND DISAGREEMENT WITH THE STRENGTH/TIMING OF THIS SYSTEM...THERE IS ENOUGH AGREEMENT TO GO CONTINUE CHANCE OF SHRA OVER PARTS OF THE CWA FROM WEDNESDAY NIGHT INTO EARLY FRIDAY. THE FORECAST DEPTH OF THIS CLOSED LOW WILL NOT BE AS DEEP AS THE ONE CURRENTLY MOVING ACROSS THE PLAINS AND FORECAST SOUNDINGS ARE RELATIVELY WARM...SO HAVE NOT MENTION OF WINTRY PRECIPITATION. BRITT/BYRD && .AVIATION... /1201 AM CDT SUN MAR 21 2010/ PRIMARY CONCERN THIS TAF PD CONTINUES TO BE PTYPE AT KUIN/KCOU AS WARMER AIR WRAPS INTO THE DEEPENING LOW PRESSURE SYSTEM. -SN HAS TRANSITIONED TO A MIX OF -PL /PER SPOTTER REPORTS/ AND -FZRA. GUSTY WINDS WILL CONTINUE THROUGH MOST OF THE 24HR TAF PD BEFORE DECREASING AS THE SYSTEM MOVES AWAY FM THE AREA. SPECIFICS FOR KSTL...SPOTTY -RA CONTINUES TO PLAGUE KSTL/KSUS TONIGHT AND HAVE COVERED THIS WITH A TEMPO GROUP SINCE IT IS DIFFICULT TO TIME EACH BATCH OF RAIN. CIGS WILL RISE AND MAY BECOME VFR TOWARDS THE END OF THE TAF PD. KANOFSKY && .LSX WATCHES/WARNINGS/ADVISORIES... MO...WINTER WEATHER ADVISORY UNTIL 1 PM CDT THIS AFTERNOON FOR AUDRAIN MO-BOONE MO-CALLAWAY MO-COLE MO-KNOX MO-LEWIS MO- MARION MO-MONITEAU MO-MONROE MO-RALLS MO-SHELBY MO. IL...WINTER WEATHER ADVISORY UNTIL 1 PM CDT THIS AFTERNOON FOR ADAMS IL. && $$ WFO LSX