FXUS62 KJAX 150821 AFDJAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSONVILLE FL 321 AM EST SAT DEC 15 2007 ...HIGH RAIN CHANCES THIS AFTERNOON & TONIGHT WITH A SLIGHT RISK OF SEVERE STORMS... .SYNOPSIS...MOISTURE ASSOCIATED FROM THE REMNANTS OF OLGA IS STEADILY INCREASING NORTHWARD OVER THE FL PENINSULA. SCATTERED SHOWERS ARE DEVELOPING FROM A WEAK SFC TROUGH THAT EXTENDS OVER OUR FL COASTAL WATERS ACROSS CENTRAL FL. A QUASI-STATIONARY FRONT APPEARS TO BE DRAPED ALONG THE GA COAST TO NEAR THE FL-GA STATELINE MAINLY MARKED BY A DEW PT GRADIENT AND A THINNING AREA OF CLOUDS. PATCHY DENSE FOG IS DEVELOPING NORTH OF THIS FEATURE ACROSS OUR INLAND GA ZONES BUT BELIEVE CLOUD COVER INCREASING FROM THE SOUTH WILL PRECLUDE WIDESPREAD FOG DEVELOPMENT THIS MORNING SO DO NOT ANTICIPATE AN ADVISORY WILL BE NEEDED. UPSTREAM A POTENT STORM SYSTEM IS PHASING WEST OF THE LOWER MISSISSIPPI RIVER VALLEY. .SHORT TERM...TODAY THROUGH MON... A DRASTIC CHANGE IN STORE AS OUR UNSEASONABLE WARM SPELL COMES TO AN END FOLLOWING THE PASSAGE OF A STRONG COLD FRONT TONIGHT WITH MAX TEMP SUNDAY 15+ DEG BELOW TODAYS FORECAST HIGHS. WE ARE ALSO ANTICIPATING SOME MUCH NEEDED RAIN ASSOCIATED WITH THIS SYSTEM WITH STORM TOTAL AMOUNTS OF 2-3 INCHES IN SOME LOCATIONS. DYNAMICS ALSO SUPPORT THE POSSIBILITY OF SEVERE STORMS LATE THIS AFTN AND TONIGHT WITH THE POTENTIAL FOR DAMAGING WINDS AND MAYBE AN ISOLATED TORNADO. SPC HAS PLACED OUR WESTERN ZONES UNDER A SLIGHT RISK OF SEVERE STORMS. TODAY...MOISTURE WILL CONTINUE TO SURGE OVER THE AREA FROM THE SOUTH AND CREEP IN FROM THE WEST AS TROUGHING OVER FL LIFTS NWD AS A WARM FRONT IN ADVANCE OF THE APPROACHING COLD FRONT. DEW PTS WILL RISE INTO THE UPPER 60S ACROSS THE AREA THIS AFTN WITH POSSIBLE LOWER 70S ACROSS OUR SOUTHERN FL ZONES. ALTHOUGH THERE WILL BE A LOT OF CLOUD COVER DEVELOPING OVER THE AREA THROUGH THE DAY TODAY AND POSSIBLY AN EXPANSIVE AREA OF PRECIP...BELIEVE THAT WARM AIR AND MOISTURE ADVECTION WILL CREATE ENOUGH MODERATE LOW LEVEL INSTABILITY TO SUPPORT ISOLD TS. TONIGHT...MODELS SUGGEST A PRE-FRONTAL SQUALL LINE DEVELOPING ACROSS THE FL PANHANDLE THIS AFTN WHERE STRONG DYNAMICS WILL COLLIDE WITH GOMEX INSTABILITY. EXPECT THIS LINE WILL EDGE TOWARD OUR WESTERN ZONES LATE THIS AFTN AND PUSH THROUGH THE CWA THIS EVENING. AN IMPRESSIVE SW ORIENTED 850 MB JET OF 55+ KTS WILL TRAVERSE OUR AREA TONIGHT WITH THE SQUALL LINE WITH STRONG WIND GUSTS LIKELY IN SHRA LET ALONE TS. ALTHOUGH LOW LEVEL FLOW WILL VEER TODAY...MAGNITUDE WIND SHEAR WILL BE PRESENT WHICH COULD SUPPORT ROTATING UPDRAFTS. WILL MENTION ISOLATED SEVERE STORMS POSSIBLE IN THE HWO FOR THIS AFTN/TONIGHT AND WILL INCLUDE GUSTY WINDS IN THE ZONES. RAINFALL AMOUNTS MAY TOTAL 2-3 INCHES TONIGHT AS THE LINE PUSHES THROUGH SO THE MENTION OF HEAVY RAINFALL STILL LOOKS GOOD FOR ALL ZONES. SUN...PRECIP WILL CLEAR THE AREA IN THE MORNING WITH COLD AND DRY AIR USHERING IN THROUGH THE DAY FROM THE NNW AS A SFC RIDGE BUILDS ACROSS THE GULF COAST STATES. MAX TEMPS WILL ONLY TOP OUT IN THE MID 50S ACROSS OUR INLAND GA ZONES WITH MID 60S ACROSS OUR FL ZONES. A LAKE WIND ADVISORY WILL LIKELY BE NEEDED WITH SUSTAINED WINDS NEAR 20 MPH AND GUSTS UP TO 30 MPH. SUN NIGHT...A FREEZE IS EXPECTED INLAND. SFC WINDS SHOULD REMAIN IN THE 5-10 MPH RANGE WITH WIND CHILLS IN THE LOW-MID 20S MON MORNING INLAND. PER COLLAB WITH NEIGHBORING OFFICES...WILL DEFER A FREEZE WATCH TO LATER SHIFTS AND CONTINUE TO HIGHLIGHT THE EXPECTED FREEZE IN THE HWO. MON & MON NIGHT...THE SFC RIDGE ADVANCES FARTHER EAST AS UPPER LEVEL TROUGHING DE-AMPLIFIES. MAX TEMPS WILL BE 10+ DEG BELOW CLIMO VALUES IN THE MID 50S. MON NIGHT THE RIDGE BEGINS TO BUILD OFFSHORE OF THE ATLANTIC COAST WITH A LIGHT LOW LEVEL NE FLOW DEVELOPING... HOWEVER IDEAL RADIATIONAL COOLING CONDITIONS WILL SUPPORT A WIDESPREAD FREEZE ACROSS OUR ZONES WITH AREAS OF FROST. THERE IS THE POSSIBILITY OF OUR FIRST WIDESPREAD HARD FREEZE ACROSS INLAND SE GA AND THE SUWANNEE RIVER VALLEY OF N FL. .LONG TERM...TUE THROUGH FRI... TEMPS WILL GRADUALLY MODERATE THROUGH THE PERIOD AS ONSHORE FLOW DEVELOPS. A COASTAL TROUGH/HIGH PRESSURE WEDGE SCENARIO MAY DEVELOP WITH COOL TEMPS CONTINUING OVER OUR GA ZONES WITH WARMER TEMPS ACROSS FL AS WELL AS A CHANCE FOR COASTAL SHRA THROUGH THU. FRI A WEAK FRONT BECOMES DIFFUSE ACROSS OUR AREA WITH LITTLE MOISTURE AND DYNAMICS TO WORK WITH UNTIL A STRONGER FRONT APPROACHES NEXT WEEKEND....A SIMILAR SYNOPTIC PATTERN TO THE PAST TWO DAYS. HAVE KEPT EXTENDED POPS BELOW 20%. && .AVIATION...OCCASIONAL MVFR IS POSSIBLE OVERNIGHT MAINLY DUE TO CIGS AS STRATO-CU PUSHES NWD. ISOLD TS EXPECTED DURING THE AFTN THEN INCREASING CHANCES FOR TSRA DURING THE EVENING AS THE FRONT PASSES. WILL KEEP VCTS AFTER 18Z AND SHRA ENDING AFTER 09Z SUN. && .MARINE...SWELLS CONTINUE TO DOMINATE SEAS AND WILL KEEP SCEC FOR OFFSHORE WATERS TODAY. VEERING WINDS ARE EXPECTED THRU SUNDAY. CURRENTLY WINDS ARE E TO SE AT THE BUOYS AND WILL SHIFT TO S THIS AFTN AND W-NW SUNDAY FOLLOWING FRONTAL PASSAGE. NO CHANGES TO TIMING FOR SCA CONDITIONS LATE THIS AFTN. SCA CONDS WILL CONTINUE INTO MON WHEN PRES GRADIENT WEAKENS AS HIGH PRES BUILDS N OF AREA AND SHIFTS WINDS TO NE TUE-WED. && .FIRE WEATHER...MUCH DRIER AIR WILL FILTER INTO THE REGION BEHIND THE FRONT AND RH'S WILL FALL BELOW 35 PCT AWAY FROM THE COAST ON MONDAY. HOWEVER COOLER TEMPS AND SHORTER DAYS MAKE IT UNLIKELY A WATCH WILL BE NEEDED. && .PRELIMINARY POINT TEMPS/POPS... AMG 72 53 57 28 / 90 90 10 0 SSI 71 59 63 35 / 80 90 30 0 JAX 75 59 62 32 / 70 80 40 0 SGJ 76 62 65 36 / 60 80 40 0 GNV 79 61 63 31 / 70 80 40 0 OCF 80 62 65 32 / 70 80 40 0 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...NONE. GA...NONE. AM...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 7 PM EST MONDAY FOR ST AUGUSTINE TO FLAGLER BEACH FL 20 NM TO 60 NM OFFSHORE. SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 12 PM EST MONDAY FOR ALTAMAHA SOUND GA TO FERNANDINA BEACH FL 20 NM TO 60 NM OFFSHORE-FERNANDINA BEACH TO ST AUGUSTINE FL 20 NM TO 60 NM OFFSHORE. SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 8 AM EST MONDAY FOR ALTAMAHA SOUND GA TO FERNANDINA BEACH FL OUT 20 NM- FERNANDINA BEACH TO ST AUGUSTINE FL OUT 20 NM-ST AUGUSTINE TO FLAGLER BEACH FL OUT 20 NM. && $$ ENYEDI/TRABERT