000 FXUS64 KLIX 311344 AFDLIX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW ORLEANS LA 844 AM CDT TUE MAR 31 2009 .SOUNDING DISCUSSION... THE ATMOSPHERE HAS BECOME MOIST AND UNSTABLE WITH A LIFTED INDEX VALUE OF -5.3 AND A PRECIPITABLE WATER VALUE OF 1.35 INCHES. AT THE TIME OF LAUNCH A FEW ALTOCUMULUS CLOUDS WERE PRESENT...SINCE THEN A STRATUS DECK HAS MOVED IN. SOUTHERLY FLOW NEAR THE SURFACE CONTINUES TO BRING IN WARM MOIST AIR...GOOD SPEED SHEAR IS ALSO PRESENT. && .PREV DISCUSSION... /ISSUED 425 AM CDT TUE MAR 31 2009/ SYNOPSIS... LATEST SURFACE ANALYSIS SHOWED A DEEP 993MB LOW OVER WEST IOWA WITH A COLD EXTENDING SOUTH TO EAST OKLAHOMA TO CENTRAL TEXAS. SOUTH TO SOUTHEAST WINDS WERE NOTED OVER MID AND LOWER MISSISSIPPI VALLEY. DEWPOINT READINGS OF 60F AND GREATER WERE GENERALLY WEST OF SHV TO MSY LINE AND DEEPER MOISTURE OVER SOUTHEAST TEXAS. 00Z PW PLOTS SHOWED SHV...LCH AND CRP FROM 1 TO 1.2 INCHES AND GFS AND NAM INITIALIZED WELL WITH THIS FEATURE. UPPER AIR ANALYSIS SHOWED A CLOSED OVER CENTRAL NEBRASKA AND IR SATELLITE IMAGERY CLOUDS STREAMING WEST TO EAST NORTH MEXICO TO NORTHWEST GULF AND CONVECTION OVER NORTHEAST TEXAS. SOUNDING AT SLIDELL SHOWED SIGNIFICANT VEERING WINDS IN THE LOWER LEVELS...SEVERAL DRY LAYERS ABOVE 875MB AND WB ZERO AROUND 6500 FEET. SHORT TERM... WITH THE MAIN SYSTEM LIFTING TOWARD THE GREAT LAKES REGION...AREAL ATM WILL LOSE THE LOW LEVEL SOUTHEAST COMPONENT WIND THROUGH TODAY. AS A RESULT...VEERING WINDS WITH HEIGHT DECREASE BY MIDDAY ACCORDING TO NAM AND GFS. SRH 0-3 DECREASES FROM NEAR 400M/S AT 12Z TO 100M/S...THUS DECREASE THE TORNADIC THREAT EXCEPT ALONG THE FRONT WITH FRONTAL FORCING. SOME DRY AIR REMAINS IN THE MID LAYERS AND WB ZERO HOVERS FROM 9500 TO 10KFT TODAY AND THIS EVENING. ERGO...THE MAIN THREAT IS PROBABLY HAIL AND WINDS AND THEN TORNADO AND HEAVY RAINFALL. ALL OF THESE THREATS UNDER A SLIGHT RISK OF SEVERE WEATHER FOR THE TODAY. SUB-TROPICAL JET REMAINS THE MAIN CHARTER. THE BASE OF THE TROUGH ON WATER VAPOR SHOWED SEVERAL DISTURBANCES ALONG WITH THE SUB-JET WILL CREATE UPPER LEVEL DIVERGENCE FROM SOUTHWEST LOUISIANA TO EAST NORTHEAST EARLY TODAY. LOSING THE SOUTHEAST LOW LEVEL COMPONENT EARLY WILL ALLOW THE BULK OF THE DEEP MOISTURE TO REMAIN JUST SOUTH AND EAST OF THE FORECAST LAND AREAS AND GENERAL RAINFALL OF A HALF TO 2 INCHES MAY OCCUR. WILL HOLD OFF ON ANY FLASH FLOOD WATCHES FOR NOW...BUT WILL KEEP CATEGORICAL RAIN CHANCES TODAY THROUGH THIS EVENING. A LULL IN THE WEATHER IS EXPECTED WEDNESDAY. HOWEVER...THE FRONTAL PASSAGE THIS EVENING WILL ONLY PUSH THE MOISTURE SOUTH OVER THE NORTH GULF...WHICH WILL WAIT FOR THE NEXT SYSTEM LONG TERM... GFS AND NAM CONTINUE TO SHOW THE NEXT SYSTEM DIVING SOUTHEAST ALONG THE RED RIVER VALLEY BECOMING NEGATIVELY TILTED OVER THE ARKLATEX REGION THURSDAY MORNING. A SIGNIFICANT AMOUNT OF DRY AIR OVER TEXAS IS EXPECTED TO ENTRAIN ON WEST AND SOUTHWEST SIDE OF THE LOW AND MAY DECREASE MOISTURE AND CONVECTION QUICKLY BY LATE THURSDAY AFTERNOON. WILL MAINTAIN THE BEST CHANCE OF RAIN ACROSS SOUTHWEST AND SOUTH CENTRAL MISSISSIPPI THURSDAY AND DECREASE RAIN CHANCES BY THURSDAY EVENING. THIS SYSTEM WILL LIFT NORTHEAST TOWARD THE GREAT LAKES...LEAVING THE DRY WEST FLOW ALOFT OVER THE THROUGH SUNDAY. THE NEXT SYSTEM ON SUNDAY IS COMING IN WEAKER AS FAR AS WEATHER ACROSS THE CENTRAL GULF COAST SUNDAY...THUS WILL MAINTAIN JUST 20 PERCENT SUNDAY. AVIATION... /PRELIMINARY 12Z TAF ISSUANCE/ MVFR TO VFR CEILINGS EXPECTED TODAY...WITH ANY IFR OR LOWER CONDITIONS LIMITED TO AREAS OF PRECIPITATION. COLD FRONT WILL MOVE FROM WEST TO EAST DURING THE DAYTIME AND EVENING HOURS WITH A PERIOD OF THUNDER EXPECTED. POST FRONTAL...VFR CONDITIONS RETURN. 35 MARINE... GRADIENT HAS ACTUALLY RELAXED THIS MORNING WITH NORTHEASTERN GULF BUOYS...INCLUDING 42040...REPORTING WINDS AROUND 10 KNOTS. HAVE DROPPED THE EXERCISE CAUTION FOR MOST OF THE DAYTIME HOURS. GRADIENT SHOULD NOT REALLY TIGHTEN MUCH UNTIL THE FRONT GETS CLOSER LATER IN THE DAY. WINDS WILL MOVE INTO THE EXERCISE CAUTION RANGE THIS AFTERNOON...BUT DUE TO SLIGHTLY SLOWER FRONTAL MOVEMENT...ANY ADVISORY LEVEL WINDS EXPECTED TO HOLD OFF UNTIL AROUND SUNRISE ON WEDNESDAY. THEREFORE HAVE LOWERED ADVISORY TO EXERCISE CAUTION. ALL GUIDANCE INDICATES ANY ADVISORY LEVEL WINDS SHOULD BE FOR ABOUT 6 HOURS OR LESS WEDNESDAY MORNING. MUCH BETTER POTENTIAL WITH STRONGER SYSTEM ON THURSDAY...AND ANOTHER ONE SATURDAY NIGHT OR SUNDAY. WITH FAST MOVING FRONTAL SYSTEMS...WINDS ARE NOT EXPECTED TO MAINTAIN DIRECTION FOR A LONG ENOUGH PERIOD TO SET UP A SIGNIFICANT SWELL TRAIN OVER THE NEXT FEW DAYS. THIS SHOULD ALLEVIATE ANY CONCERNS OF A LONG PERIOD OF COASTAL FLOODING. 35 && .PRELIMINARY POINT TEMPS/POPS... MCB 77 50 72 58 / 80 30 10 20 BTR 77 52 73 59 / 80 30 10 20 MSY 77 56 71 64 / 80 60 10 20 GPT 74 55 70 63 / 80 60 20 20 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...NONE. GM...NONE. MS...NONE. GM...NONE. && $$