AFDLIX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW ORLEANS LA 741 AM CDT MON JUN 27 2011 .UPDATE... WILL BE ISSUING UPDATED ZONE AND MARINE FORECAST TO INCREASE RAIN CHANCES TO 20 PERCENT ACROSS THE COASTAL WATERS AND ALL OF THE SOUTH SHORE AREA AS CONVECTION IS A LITTLE MORE PRONOUNCED AND SOMEWHAT ORGANIZED ALONG AN APPARENT MOISTURE SURGE...AS SUGGESTED BY 00Z WRF RUN. CONVECTION SHOULD STRUGGLE TO PENETRATE TOO FAR INLAND GIVEN DEGREE OF SUBSIDENCE ALOFT OVER LAND. THE SOUNDING IS QUITE SUPPORTIVE OF WATERSPOUT DEVELOPMENT THIS MORNING ALONG WITH WET MICROBURSTS. NO OTHER CHANGES AT THIS TIME. 24/RR && .PREV DISCUSSION... /ISSUED 418 AM CDT MON JUN 27 2011/ SHORT TERM... TODAY`S WEATHER WILL BE DOMINATED BY VERY LARGE AND STRONG SUBSIDENCE RIDGE ALOFT CENTERED OVER TEXAS AND RIDGING THROUGH THE LOWER MISSISSIPPI RIVER VALLEY. THIS IS COUPLED WITH LOW LEVEL BERMUDA RIDGE EXTENSION FLOW PATTERN NEAR THE SURFACE. TEMPERATURES HAVE HELD IN THE UPPER 70S TO MID 80S OVERNIGHT THUS FAR DUE TO THE HIGH LOW LEVEL MOISTURE CONTENT COINCIDING WITH SUBSIDENCE ALOFT. VERY WARM TEMPERATURES ARE IN THE OFFING ALONG WITH HEAT INDEX READINGS IN THE 105-110 RANGE TODAY. HEAT STRESS GUIDANCE STILL DOES NOT INDICATE CRITERIA FOR ADVISORY THOUGH CUMULATIVE AFFECTS MAY ONSET FOR THE NEXT FEW DAYS. INDICATED AN UNMENTIONABLE 10 PERCENT RAIN CHANCE TODAY FOR MOST OF THE AREA EXCEPT 20 PERCENT SMALL AREA GENERAL NEW ORLEANS METRO AREA THROUGH TERREBONNE PARISH FOR LAKE-GULF BREEZE CONVERGENCE CONVECTION MID TO LATE AFTERNOON...SIMILAR TO SUNDAY. AGAIN...ANY DEVELOPMENT WILL BE SHORT-LIVED PULSE TYPE ISOLATED CELLS. DOWN BURST POTENTIAL IS HIGH UNDER THE INITIAL CELLS ALONG WITH WATERSPOUT POTENTIAL DUE TO LOW SHEAR BUT STRONG VERTICAL STRETCHING IN DEVELOPING STAGES. TUESDAY MAY BE SIMILAR THOUGH COVERAGE WILL LIKELY BE EVEN MORE ISOLATED DUE TO INCREASED SUBSIDENCE ALOFT. LONG TERM... BERMUDA RIDGE PATTERN PERSIST THROUGH MUCH OF THE FORECAST PERIOD THOUGH A WEAK TROUGH OF LOW PRESSURE SETTLES INTO THE AREA THURSDAY AS A BACK-DOOR FRONTAL FEATURE ON THE PERIPHERY OF THE RIDGE EXTENSION. THIS MAY ALLOW FOR APPALACHIAN DRAINAGE TO REACH SOME OF THE LARGER RIVER VALLEYS TO BRING A MORE OR TWO OF DRIER AND SOMEWHAT COOLER LOCALIZED TEMPERATURES IN THE MORNING FRIDAY...NAMELY KPQL AND KASD AREAS PRONE TO RIVER VALLEY DRAINAGE AFFECTS. SEE MARINE SECTION REGARDING GULF LOW POTENTIAL IN COMING DAYS AND POSSIBLE IMPACTS IN THE COASTAL WATERS. AVIATION... VFR CONDITIONS TO PREVAIL AT ALL TERMINALS NEXT 24-36 HOURS. ONLY AVIATION CONCERN WILL BE LOCALIZED POTENTIAL FOR DOWN BURSTS AND FC/WATERSPOUTS UNDER DEVELOPING TCU/EARLY STAGE CB ALONG LAKE AND GULF BREEZE CONVERGENCE ZONE. THIS MAY BE A GREATER ISSUE FOR KMSY AND KHUM BETWEEN 19Z-22Z BUT 20 PERCENT PROBABILITY TOO LOW TO MENTION IN TAF AT THIS TIME. HAZARDOUS WEATHER OUTLOOK WILL OFFER DETAILS ON THREAT POTENTIAL. MARINE... STEADY STATE BERMUDA RIDGE EXTENSION MAINTAINING ONSHORE FLOW FOR THE FORESEEABLE FUTURE. A SWELL TRAIN GENERATING FROM THE YUCATAN CHANNEL AND FLORIDA STRAITS EMANATING NORTHWESTWARD AND PROVIDING A DEVELOPING GROUND SWELL THAT WILL LIKELY PERIOD AT 8-9 SECONDS AT PEAK TUESDAY AND WEDNESDAY. WATCHING CLOSELY AN OBVIOUS UPPER LEVEL LOW PRESSURE CIRCULATION OVER THE CENTER OF THE YUCATAN PENINSULA AND MOVING WEST. THIS FEATURE IS BEING INITIALIZED IN ALL THE CONVENTIONAL HEMISPHERIC MODELS WHICH NOW SHOW CONSENSUS ON DEVELOPING A SURFACE REFLECTION LOW UPON REACHING THE EASTERN BAY OF CAMPECHE. THE VERTICAL STACK NATURE OF THE FEATURE SUGGEST A BAROCLINIC SYSTEM THAT MAY ATTAIN HYBRID...LOW END TROPICAL CHARACTERISTICS AROUND 95W LATITUDE. SOME ISSUES MAY BE PROXIMITY OF ANY SURFACE LOW TO UPPER COL...A MASS NEUTRAL REGIME WHERE CYCLOGENESIS IS UNFAVORABLE. IF THE SURFACE FEATURE REMAINS JUST SOUTH OF UPPER TUTT COL...THEN A WESTWARD TRACK IS IMMINENT ALONG WITH SOMEWHAT FAVORABLE UPPER EXHAUST MECHANISM FOR SLOW ORGANIZATION PRIOR TO LANDFALL ALONG THE CENTRAL MEXICAN COAST...AS ALL THE CONVENTIONAL MODELS INDICATE. IT SHOULD BE NOTED NONE OF THE TROPICAL MODELS WERE INVOKED AS YET BUT MAY START WITH 12Z ANALYSIS INITIATION TODAY. DESPITE FUTURE INTEGRITY OF THIS SYSTEM...MODERATE SOUTHEAST TO EASTERLY FLOW IS ANTICIPATED TO PERSIST ALONG THE NORTH-CENTRAL GULF COAST AS GRADIENT TIGHTENS SOMEWHAT AND SWELL TRAIN SLOWLY DAMPENS LATER IN THE WEEK. && .PRELIMINARY POINT TEMPS/POPS... MCB 95 75 96 75 / 10 0 10 10 BTR 95 76 95 78 / 10 0 10 10 ASD 92 76 93 77 / 10 0 10 10 MSY 93 79 93 80 / 20 0 10 10 GPT 92 76 93 78 / 10 0 10 10 PQL 93 74 94 76 / 10 10 10 10 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...NONE. GM...NONE. MS...NONE. GM...NONE. && $$