778 FXUS63 KLSX 251125 AFDLSX AREA FORECAST DISCUSSION...UPDATED AVIATION NATIONAL WEATHER SERVICE ST LOUIS MO 525 AM CST MON FEB 25 2013 .SHORT TERM... ISSUED AT 341 AM CST MON FEB 25 2013 (TODAY) CLOSED LOW WILL MOVE ACROSS NORTHERN TEXAS AND INTO SOUTHEAST OKLAHOMA TODAY. MEANWHILE...THE ATTENDANT SURFACE LOW WILL DEEPEN AS IT MOVES NORTHEAST FROM CENTRAL TEXAS TO THE ARKLATEX REGION BY 00Z. EAST WIND TO INCREASE AS PRESSURE GRADIENT TIGHTENS ACROSS THE REGION. A TYPICAL THICKENING AND LOWERING CLOUD FORECAST AS TOP DOWN SATURATION BEGINS IN ADVANCE OF THE STORM SYSTEM. TEMPERATURES TO BE FAIRLY SIMILAR TO YESTERDAY AS INCREASING CLOUD COVER SHOULD OFFSET SLIGHTLY WARMER ATMOSPHERE AND START TO THE DAY. CARNEY && .LONG TERM... ISSUED AT 341 AM CST MON FEB 25 2013 (TONIGHT THROUGH SUNDAY) PRIMARY FOCUS CONTINUES TO BE THE IMPENDING WINTER STORM TONIGHT. WHILE THE MASS FIELDS IN THE NCEP MODEL SUITES ARE VERY CLOSE WITH RESPECT TO THE POSITION AND TRACK OF THIS STORM...THERMAL SHENANIGANS CONTINUE ON A RUN-TO-RUN BASIS. THE GENERAL IDEA REMAINS THE SAME: AS THE LOW MOVES INTO ARKANSAS THE OVER ALL TROF STRUCTURE WILL BECOME NEGATIVELY TILTED OVERNIGHT AND THE STORM WILL BEGIN MOVING NORTHEAST...CROSSING THE BOOT HEEL TUESDAY AROUND 18Z AND INTO THE OHIO VALLEY BY 00Z WEDNESDAY. PRECIPITATION WILL OVERSPREAD THE AREA FROM THE SOUTHWEST THIS EVENING AND IT SHOULD BE RAINING/SNOWING OVER THE ENTIRE AREA BY MIDNIGHT. STRONG INDICATIONS OF A TROWAL ON BOTH THE GFS AND NAM AS WARM AIR WRAPS AROUND THE LOW LEVEL CIRCULATION. 850MB ISOTHERMS HAVE A VERY PRONOUNCED WESTWARD KINK AS THE STORM PASSES ACROSS SOUTHEAST MISSOURI. THE NAM IS COOLER THAN THE GFS...AND THE ECMWF IS COOLER STILL. HAVE TRIED TO USE A COMBINATION OF THE THREE TO FORECAST PRECIP TYPES AND CHANGE OVER TIMES. MODEL SOUNDINGS INDICATE AN ISOTHERMAL LAYER RIGHT AROUND ZERO DURING THE EVENING STRETCHING FROM COLUMBIA UP TO QUINCY. THE SOUTHERN END OF THAT LINE DOES HAVE A WARM WEDGE OF AROUND 2C BELOW 850MB WHICH INDICATES THE PRECIP SHOULD EITHER START AS LIQUID...OR PERHAPS A SLEET/SNOW MIX. IT'S STILL UNCLEAR HOW LONG IT WILL TAKE FOR THE PRECIP TO BECOME ALL SNOW...OR HOW FAR EAST THE RAIN-SNOW LINE WILL PROGRESS OVERNIGHT. AS MENTIONED EARLIER...THE GUIDANCE JUST CAN'T SEEM TO COME TO A CONSENSUS. NEEDLESS TO SAY...THERE WILL LIKELY BE A VERY TIGHT GRADIENT BETWEEN AREAS THAT GET LITTLE OR NO SNOW...AND AREAS THAT GET WARNING CRITERIA SNOW. REGARDLESS...IT LOOKS LIKE AREAS FROM COLUMBIA TO QUINCY AND POINTS WEST WILL GET 6 TO 8 INCHES OF SNOW WITH LOCALLY HIGHER AMOUNTS. WILL THEREFORE ISSUE A WINTER STORM WARNING WITH A BUFFER OF WINTER WEATHER ADVISORY ONE ROW OF COUNTIES EAST. EXPECT THE REMAINDER OF THE AREA NOT TO GET ENOUGH SNOW TO JUSTIFY HEADLINES. PRECIPITATION SHOULD TAPER OFF TUESDAY AFTERNOON...BUT ANOTHER SHORTWAVE WILL DIP IN BEHIND THE THE STORM TUESDAY NIGHT AND MOVE RAPIDLY EAST INTO THE OHIO VALLEY BY WEDNESDAY NIGHT. LOOKS LIKE THERE COULD BE A ANOTHER QUICK SHOT OF SNOW WITH THIS SECONDARY SHORTWAVE. MODEL QPF IS LIGHT...GENERALLY LESS THAN 0.1 INCH SO AM NOT EXPECTING TO NEED ADDITIONAL HEADLINES AT THIS TIME. THE UPPER LEVEL PATTERN BECOMES HIGHLY AMPLIFIED IN THE WAKE TUESDAY'S STORM. A DEEP LONGWAVE TROF WILL DIG IN OVER THE EASTERN SEABOARD WITH A STRONG RIDGE OVER THE ROCKIES. THIS WILL KEEP US IN NORTHERLY FLOW ALOFT. THE REMAINDER OF THE FORECAST LOOKS COLD WITH TEMPERATURES RUNNING ABOUT 10 DEGREES BELOW NORMAL THROUGH THE PERIOD. WEATHER SHOULD ALSO BE DRY WITH THE EXCEPTION OF SOME FLURRIES AS ADDITIONAL SHORTWAVES DIVE SOUTH ACROSS THE AREA IN THE NORTHERLY FLOW. CARNEY && .AVIATION... ISSUED AT 517 AM CST MON FEB 25 2013 WINTER STORM APPROACHING FROM THE SOUTHWEST WILL CAUSE CEILINGS TO LOWER THROUGHOUT THE DAY...WITH PRECIPITATION SPREADING FROM SOUTH TO NORTH ACROSS THE REGION THIS EVENING. EXPECT RAIN TO MIX AND CHANGE TO SNOW AT COLUMBIA AND QUINCY OVERNIGHT...WITH ONLY RAIN FOR ST. LOUIS METRO TERMINALS. NORTHEAST WIND WILL INCREASE AS PRESSURE GRADIENT TIGHTENS OVER THE REGION. COULD SEE GUSTS TO 30KTS. IFR CEILING AND VISIBILITY EXPECTED WITH HEAVIEST BAND OF PRECIPITATION LATE THIS EVENING THROUGH TUESDAY MORNING. SPECIFICS FOR KSTL... THICKENING AND LOWERING CEILING EXPECTED TODAY...WITH RAIN MOVING INTO THE TERMINAL COMPLEX THIS EVENING. CONDITIONS TO LOWER TO IFR WITH HEAVIEST PRECIPITATION BETWEEN 06Z AND 15Z. NORTHEAST WIND TO INCREASE TO NEARLY 20KT WITH GUSTS APPROACHING 30KT. WIND TO DECREASE BRIEFLY ON TUESDAY AS LOW PRESSURE MOVES JUST TO THE SOUTH OF THE TERMINAL. CVKING && .PRELIMINARY POINT TEMPS/POPS... SAINT LOUIS 45 34 37 30 / 10 100 80 50 QUINCY 40 29 32 26 / 0 100 100 60 COLUMBIA 42 31 33 26 / 20 100 80 50 JEFFERSON CITY 45 32 34 27 / 40 100 80 50 SALEM 47 36 41 31 / 5 100 80 40 FARMINGTON 49 37 41 29 / 20 100 60 30 && .LSX WATCHES/WARNINGS/ADVISORIES... MO...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM CST TUESDAY FOR AUDRAIN MO-BOONE MO-KNOX MO-LEWIS MO-MARION MO-MONITEAU MO-MONROE MO-RALLS MO-SHELBY MO. WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 PM CST TUESDAY FOR CALLAWAY MO-COLE MO-MONTGOMERY MO-OSAGE MO-PIKE MO. IL...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM CST TUESDAY FOR ADAMS IL-BROWN IL. WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 PM CST TUESDAY FOR PIKE IL. && $$ WFO LSX