FXUS62 KJAX 120726 AFDJAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSONVILLE FL 320 AM EDT THU APR 12 2007 .SYNOPSIS...A THIN LINE OF PRE-FRONTAL SHRA IS APPROACHING OUR WESTERN GA ZONES THIS HOUR WITH THE STRONGER STORMS TO OUR N IN VC OF THE WARM FRONT. DECENT INSTABILITY REMAINS OVER OUR GA ZONES NEAR THE ALTAMAHA RIVER SO ANTICIPATE THAT THE THIN LINE OF SHRA WILL HOLD TOGETHER AS IT CROSSES OUR GA ZONES EARLY THIS MORNING. SFC ANALYSIS INDICATES SFC LOW ADVANCING NE OVER GA/SC WITH TROUGHING EXTENDING SWD THROUGH THE FL PANHANDLE WHILE A SFC RIDGE HOLDS ACROSS S FL. MEAN LAYER WSW CONTINUES OVER THE SE REGION. .SHORT TERM...TODAY THROUGH SAT... AFTER ISOLD SHRA AND PATHS DRIZZLE CROSS OUR GA ZONES IN ADVANCE OF THE APPROACHING FRONT...EXPECT CLEARING SKIES INTO THIS AFTN AS WEAK FRONT SLOWLY SAGS SWD THROUGH OUR CWA WITH DRIER AIR FILTERING IN FROM THE WNW. BREEZY CONDITIONS ARE EXPECTED BY LATE MORNING IN WAKE OF FRONT WITH SUSTAINED SPEEDS 15-20 MPH AND POSSIBLE GUSTS UP TO 25 MPH THIS MORNING ACROSS OUR GA ZONES WHERE PGRAD WILL STRONGER AS LOW PRESSURE PULLS NE OVER THE MID-ATLANTIC. WARM MEAN LAYER WSW FLOW WILL CONTINUE OVER THE AREA WHICH WILL KEEP MAXES WARM IN THE MID TO UPPER 80S UNDER MOSTLY SUNNY SKIES. TONIGHT SFC RIDGE BUILDS ESE FROM THE MID WEST REGION WHILE UPPER LEVEL RIDGING AMPLIFIES. COLD AIR DRAINAGE WILL DROP MINS INTO THE MID-UPPER 40S ACROSS OUR GA ZONES AND THE SUWANNEE RIVER VALLEY...WITH LOWER 50S ALONG THE COAST UNDER MOSTLY CLEAR SKIES. FRI THE SFC RIDGE SHIFTS OFFSHORE OF THE SE ATLANTIC COAST BRINGING US A LIGHT ONSHORE FLOW WHICH WILL FOCUS WARMER TEMPS FURTHER INLAND W OF HIGHWAY 301 WHILE KEEPING THE COAST SEVERAL DEG COOLER IN THE MID-UPPER 70S UNDER SUNNY SKIES. FRI NIGHT INFLUX OF LOW LEVEL MOISTURE...MOSTLY CLEAR SKIES AND DECOUPLING WILL FAVOR AREAS OF FOG DEVELOPMENT ACROSS OUR SE FL ZONES BY DAYBREAK SAT MORNING. MIN TEMPS WILL REBOUND SEVERAL DEG DEG INTO THE MID 50S TO LOWER 60S AS WAA INCREASES. SAT NEXT FRONTAL SYSTEM WILL MOVE INTO THE SE REGION. WINDS WILL VEER FROM SE TO SW THROUGH THE DAY AND BECOME BREEZY BY AFTN...WITH INCREASING GOMEX MOISTURE OVER OUR CWA INCREASING CLOUD COVER. WAA WILL KEEP MAX TEMPS IN THE MID 80S. EXPECT SCT TSRA SAT AFTN TO BE ENCROACHING UPON OUR WESTERN GA ZONES WITH A SLIGHT CHANCE OF DIURNAL CONVECTION POSSIBLE ELSEWHERE. SAT NIGHT EXPECT A DEFINED PRE-FRONTAL SQUALL LINE WILL PUSH THROUGH OUR OUR CWA. THE MAIN CONCERN WILL BE STRONG WINDS ASSOCIATED WITH SQUALL LINE DOWNBURSTS AND STRONG PRESSURE RISES TRAILING THE FRONT WITH IMPRESSIVE 850 MB WINDS OF 50-60 KTS AND A SCREAMING UPPER LEVEL JET OF 100-130 KTS ROUNDING THE BASE OF A DEEP UPPER TROUGH CARVING OUT ACROSS THE LOWER MS RIVER VALLEY. A LAKE WIND ADVISORY MAY BE REQUIRED SAT NIGHT JUST DUE TO THE PRESSURE GRADIENT FIELD. DYNAMICS AND MOISTURE FIELDS NOT ONLY LOOK SUPPORTIVE OF MAINTAINING WELL DEFINED SQUALL LINE...BUT ALSO LOOK FAVORABLE FOR BRINGING US STORM TOTAL RAINFALL AMOUNTS OF 2 INCHES. WILL CONTINUE TO ADVERTISE LIKELY POPS ASSOCIATED WITH THIS SYSTEM SAT NIGHT AND HIT WIND CONCERNS A LITTLE STRONGER IN THE HWO. .LONG TERM...SUN THROUGH THU... HAVE CONTINUED WITH SCATTERED TSRA EARLY SUN AS PRE-FRONTAL SQUALL LINE PUSHES THROUGH THE AREA. CLEARING CONDITIONS EXPECTED SUN AFTN AS AMPLIFIED MEAN RIDGE BUILDS IN FROM THE WEST AND PUSHES FRONT TO OUR S. LAKE WIND ADVISORY POSSIBLE WIND ADVISORY CONDITIONS LIKELY BY SUN AFTN WITH GRADIENT WINDS OF 20-25 MPH AND HIGHER GUSTS LIKELY DUE TO 850 MB WINDS ADVERTISED AROUND 50 KTS MIXING DOWN WITH STRONG CAA. COLD NNW FLOW WILL CONTINUE INTO SUN NIGHT WITH MINS DROPPING INTO THE 40S WITH MAXES ONLY WARMING INTO THE LOW 70S MON AS AN OMEGA BLOCK DEVELOPS WITH OUR AREA UNDER THE INFLUENCE OF MEAN RIDGING TO OUR WEST. TEMPS GRADUALLY REBOUND TOWARD NEAR CLIMO VALUES TUE...THEN RIDGING DE-AMPLIFIES TUE NIGHT INTO WED AS A WEAK FRONT APPROACHES AND BRING US LOW RAIN CHANCES WED NIGHT INTO THU. HAVE CAPPED POPS AT 20-30% WITH CLEARING CONDITIONS THU AFTN. && .AVIATION... IFR TO MVFR CIGS WILL BE POSSIBLE THROUGH THE EARLY MORNING HOURS AT TAF SITES AS PRE-FRONTAL LOW CIGS PUSH ACRS THE FORECAST AREA. PRE-FRONTAL LLWS POSSIBLE AT ALL TAF SITES AS SWLY WINDS WILL CONTINUE AT AROUND 30 KNOTS. VFR CONDS WILL DEVELOP BY THE MID TO LATE MORNING HOURS AND CONTINUE THROUGH TONIGHT. && .MARINE... NO HEADLINES EXPECTED AS SWLY WINDS AHEAD OF THE FRONT VEER AROUND TO THE W/NW LATER TODAY...THEN TO THE N/NE ON FRIDAY. WINDS WILL INCREASE SHARPLY AHEAD OF NEXT LOW PRESSURE OUT OF THE SOUTH ON SATURDAY TO SMALL CRAFT ADVISORY LEVELS WITH GALE FORCE WINDS STILL EXPECTED ON SUNDAY BEHIND DEPARTING LOW WITH DECREASING WINDS ON MONDAY. && .FIRE WEATHER... RED FLAG EVENT ACRS MOST OF NE FL AND INLD SE GA STILL EXPECTED TO MATERIALIZE THIS AFTERNOON AS DRIER AIR FILTERS IN BEHIND FRONTAL PASSAGE THIS MORNING AND MODERATE WEST WINDS OF 15 TO 20 MPH WITH GUSTS TO 25 MPH MIX DOWN THIS AFTERNOON. DRY AIR IN PLACE WILL ALLOW FOR ANOTHER RED FLAG EVENT ACROSS INLAND FORECAST AREAS OF SE GA AND NE FL AS ONSHORE FLOW DEVELOPS ALONG THE COAST. HAVE LEFT AS A FIRE WEATHER WATCH FOR NOW AND LET DAY SHIFT UPGRADE TO WARNING IF TRENDS CONTINUE. && .PRELIMINARY POINT TEMPS/POPS... AMG 82 44 82 53 / 20 0 0 0 SSI 81 52 74 61 / 10 0 0 0 JAX 86 49 79 56 / 10 0 0 0 SGJ 85 55 76 62 / 10 0 0 0 GNV 87 49 84 57 / 10 0 0 0 OCF 88 50 86 57 / 10 0 0 0 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...FIRE WEATHER WATCH FROM FRIDAY AFTERNOON THROUGH FRIDAY EVENING FOR ALACHUA-BAKER-BRADFORD-CLAY-COLUMBIA-DUVAL-GILCHRIST- HAMILTON-MARION-NASSAU-PUTNAM-SUWANNEE-UNION. RED FLAG WARNING FROM NOON TODAY TO 8 PM EDT THIS EVENING FOR ALACHUA-BAKER-BRADFORD-CLAY-COLUMBIA-DUVAL-GILCHRIST- HAMILTON-NASSAU-SUWANNEE-UNION. GA...RED FLAG WARNING FROM 1 PM THIS AFTERNOON TO 7 PM EDT THIS EVENING FOR APPLING-ATKINSON-BACON-BRANTLEY-CHARLTON-CLINCH- COFFEE-ECHOLS-JEFF DAVIS-PIERCE-WARE-WAYNE. FIRE WEATHER WATCH FROM FRIDAY AFTERNOON THROUGH FRIDAY EVENING FOR APPLING-ATKINSON-BACON-BRANTLEY-CHARLTON-CLINCH-COFFEE- ECHOLS-JEFF DAVIS-PIERCE-WARE-WAYNE. AM...NONE. && $$ ENYEDI/HESS