000 TTAA00 KLIX 210853 AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW ORLEANS LA 345 AM CDT TUE SEP 21 1999 WHILE HARVEY MOVES EAST ACROSS FLORIDA...OUR FOCUS TURNS TO AN UNSEASONABLY STRONG COLD FRONT...MORE TYPICAL OF LATE OCTOBER THAN SEPTEMBER. AT 3 AM...COLD FRONT EXTENDED ACROSS CENTRAL MISSISSIPPI INTO CENTRAL LOUISIANA. WATER VAPOR LOOPS OVERLAYED WITH RUC ANALYZED WINDS...VORTICITY AND PROFILER PLOTS SHOW LEAD VORT MAX MOVING INTO CAROLINAS...SECONDARY VORT MAX OVER S ARKANSAS...A LARGE 100 KT PLUS 250 MB JET FROM THE TEXAS PANHANDLE INTO S ARKANSAS AND NW MISSISSIPPI...AND THE MAIN MID/UPPER TROUGH EXTENDING FROM THE GREAT LAKES INTO THE MID MISSISSIPPI VALLEY AND CENTRAL PLAINS. UVV ASSOCIATED WITH THE UPPER LEVEL JET AND CYCLONIC FLOW EXTENDS WELL NORTH OF THE COLD FRONT WITH MULITLAYERED CLOUDS AND RAIN AS FAR NORTH AS NW ARKANSAS AND SE MISSOURI WITH SOME ELEVATED CONVECTION/LIGHTNING NOTED OVER S ARKANSAS. THE NGM/ETA SOLUTIONS SEEM BEST FOR THE GULF COAST REGION FOR THIS FORECAST WITH THE AVN APPEARING TOO WEAK WITH THE DEVELOPING SURFACE GRADIENT AND WIND IN LATER PERIODS. BRIDGING OF VERY COOL AND DRY SURFACE HIGH PRES SHOULD CAUSE THE COLD FRONT TO JUMP SE TO THE COAST DURING THE MORNING HOURS AND PUSH OFFSHORE DURING THE AFTERNOON. UVV ASSOCIATED WITH THE JET...500 MB PVA...AND LOW LEVEL MOISTURE FLUX CONVERGENCE SHOULD BE SUFFICIENT TO SUPPORT WIDELY SCATTERED SHOWERS TODAY ACROSS THE FORECAST AREA...MAINLY POST- FRONTAL. RADAR SHOWS WIDELY SCATTERED TO SCATTERED SHOWER ACTIVITY OVER CENTRAL LOUISIANA TENDING TO DISSIPATE AS IT MOVES INTO SW MISSISSIPPI...BUT DYNAMICS SHOULD BE SUFFICIENT FOR ADDITIONAL SHOWER DEVELOPMENT THROUGH THE DAY. CLOUDS AND COLD AIR ADVECTION SHOULD HOLD TEMPS DOWN CLOSE TO GUIDANCE VALUES IN THE LOWER TO MID 80S. TONIGHT AND WEDNESDAY...SUBSIDENCE AND ADVECTION OF VERY DRY AND COOL AIR WILL CLEAR OUT THE CLOUDS AND USHER IN DEWPOINTS IN THE 50S WITH EVEN SOME UPPER 40S NORTH. THIS COOL DRY AIR PASSING OVER THE WARM LAKE AND COASTAL WATERS WILL CAUSE NORTH WINDS TO PICK UP TO AT LEAST 20 KT AND GUSTY OVER THE TIDAL LAKES AND 20 TO 25 KT AND GUSTY OVER THE SE LOUISIANA AND MISSISSIPPI COASTAL WATERS BY TONIGHT. OVER LAND...VERY REFRESHING CLEAR COOL NIGHTS AND MILD SUNNY DAYS WILL BE ON TAP TONIGHT THROUGH FRIDAY WITH DAYTIME TEMPS MODERATING BACK TO THE MID 80S BY FRIDAY OR SATURDAY. WITH THE STRONG WINDS ACROSS LAKE PONTCHARTRAIN TONIGHT...THERE WILL PROBABLY NOT BE MORE THAN 5 DEGREES TEMP DIFFERENCE BETWEEN NORTH AND SOUTH SHORE. LIGHTER WINDS WEDNESDAY NIGHT WILL PROBABLY PRODUCE A 10 DEGREE DIFFERENCE BETWEEN NORTH AND SOUTH SHORE. COOL NUMBERS FOLLOW... MCB 82/55/76/48 2000 BTR 84/57/77/52 2000 MSY 86/62/78/60 2100 BIX 86/60/79/55 2000 .NEW...SMALL CRAFT ADVISORY COASTAL WATERS AQQ TO ATCHAFALAYA RIVER LA...NONE. MS...NONE. 22