768  
FXUS62 KJAX 201750  
AFDJAX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE JACKSONVILLE FL  
150 PM EDT WED SEP 20 2017  
   
NEAR TERM...TODAY THROUGH THU
 
 
TODAY...A TRAILING WAKE TROUGH FROM TS JOSE EXTENDED SW FROM THE  
CIRCULATION AND ACROSS SOUTHERN GA THIS AFTERNOON. THIS TROUGH  
AXIS COMBINED WITH THE SEA BREEZES, DIURNAL INSTABILITY AND WEAK  
MID LEVEL FORCING FROM A DEEPENING 500 MB TROUGH AXIS DOWN THE  
ATLANTIC SEABOARD WILL BRING ISOLATED TO SCATTERED SHOWERS AND  
ISOLATED TSTORMS ACROSS INLAND SE GA THROUGH THIS EVENING, WITH A  
GRADUAL DRIFT TOWARD THE SSE TOWARD THE INTERSTATE 10 CORRIDOR OF  
NE FLORIDA. DRIER AIR OVER NE FL UNDER LOW LEVEL SUBSIDENCE WILL  
BRING MOSTLY DRY CONDITIONS AND WILL TEND TO ERODE CONVECTION  
ACROSS SE GA AND ALONG THE I-10 CORRIDOR AS IT DRIFTS FARTHER SSE  
INTO THE EVENING HOURS.  
 
TONIGHT...RAINFALL IS EXPECTED TO FADE INLAND BY MIDNIGHT OVER  
INLAND AREAS WITH PARTLY CLOUDY TO MOSTLY CLOUDY SKIES AS UPPER  
LEVEL MOISTURE INCREASES OVER THE REGION. THERE COULD BE SOME  
LINGERING SHOWERS ACROSS SE GA OR THE SUWANNEE RIVER VALLEY AFTER  
MIDNIGHT AS MID/UPPER LEVEL TROUGH AXIS DEEPENS FARTHER SOUTH, BUT  
TRENDED FORECAST WITH DIURNAL CONVECTIVE TRENDS AT THIS TIME AND  
LIMITED RAIN CHANCES TO < 14% MIDNIGHT THROUGH SUNRISE.  
SIGNIFICANT FOG FORMATION IS NOT EXPECTED DUE TO PASSING CLOUDS,  
BUT SOME LOCALIZED FOG COULD OCCUR ESPECIALLY INLAND WERE RECENT  
RAINFALL OCCURRED. LOW TEMPERATURES WILL RANGE IN THE UPPER  
60S/LOW 70S INLAND TO LOW/MID 70S ALONG THE ST JOHNS RIVER BASIN  
AND ATLANTIC COAST.  
 
THU...TRAILING WAKE SURFACE TROUGH AXIS LINGERS OVER THE AREA  
WHILE BECOMING MORE DIFFUSE AS HIGH PRESSURE NORTH OF THE REGION  
BEGINS TO STRENGTHEN, RESULTING IN A STRONGER ENE WIND FLOW FROM  
THE SURFACE UP TO 850 MB. ALOFT, AN ELONGATED TROUGH AXIS WILL DIG  
FURTHER ACROSS THE DEEP SOUTH, WHICH WILL BRING STRENGTHENING  
WESTERLY UPPER LEVEL FLOW OVER THE LOCAL AREA, AND SETTLE THE  
MOISTURE AXIS A BIT FARTHER SOUTH EXPANDING ACROSS SE GA AND NEAR  
THE I-10 CORRIDOR OR NE FL. CONTINUED WITH ISOLATED TO SCATTERED  
RAIN CHANCES THU WITH THE GREATEST CHANCES FOCUSED ACROSS OUR  
WESTERN ZONES ROUGHLY FROM JESUP TO MACCLENNY TO GAINESVILLE,  
WESTWARD, DURING THE AFTERNOON/EVENING WHERE SEA BREEZES,  
LINGERING FRONTAL FORCING AND DEEPEST MOISTURE WILL COINCIDE UNDER  
EAST COAST SEA BREEZE REGIME. CLEARING EXPECTED ALONG THE  
ATLANTIC COAST IN THE AFTERNOON/EVENING AS DRIER AIR FILTERS IN  
FROM THE ATLANTIC. HIGH TEMPERATURES WILL TREND TO SLIGHTLY BELOW  
TODAY'S MAX TEMPERATURES, GENERALLY IN THE LOW 90S/UPPER 80S  
INLAND TO MID 80S COAST WHERE A STRONGER EAST COAST SEA BREEZE IS  
EXPECTED.  
   
SHORT TERM.../THURSDAY NIGHT THROUGH SUNDAY/
 
 
HIGH PRESSURE WILL BE NORTH OF THE REGION THURSDAY NIGHT THROUGH  
SATURDAY, LEADING TO AN INCREASINGLY MOIST ONSHORE FLOW. WITH THE  
INCREASING MOISTURE EXPECT DIURNAL CONVECTION CHANCES TO INCREASE  
FRIDAY INTO SATURDAY. THE FORECAST INTO SUNDAY WILL DEPEND ON THE  
TRACK OF MARIA. AT THIS POINT, FORECAST TRACK PUTS THIS SYSTEM WELL  
TO THE EAST SUNDAY WITH RIDGING BUILDING SOUTH ACROSS FORECAST AREA.  
THIS RIDGING SHOULD PROVIDE ENOUGH SUBSIDENCE TO LIMIT CONVECTIVE  
POTENTIAL FOR SUNDAY.  
 
TEMPERATURES WILL TREND NEAR TO SLIGHTLY ABOVE NORMAL THIS PERIOD.  
   
LONG TERM.../SUNDAY NIGHT THROUGH WEDNESDAY/
 
 
MARIA IS CURRENTLY FORECAST TO TRACK TO THE NORTHEAST OF THE REGION  
THIS PERIOD. THE FLOW ON THE BACK SIDE OF THE TROPICAL SYSTEM WOULD  
THEN LEAD TO A FAIRLY DRY NORTHWESTERLY PATTERN, PROVIDING  
LIMITED CONVECTIVE POTENTIAL AND MAINLY SUNNY DAYS.  
 
WITH THE INCREASED SUNSHINE, TEMPERATURES ARE EXPECTED TO TREND  
ABOVE NORMAL THIS PERIOD.  
 

 
   
AVIATION
 
 
PREVAILING VFR CONDITIONS. RESTRICTIONS POSSIBLE IN ISOLATED  
SHOWERS OR A THUNDERSTORM LATE THIS AFTERNOON NEAR GNV, VQQ OR SSI  
BUT PROBABILITIES ARE TOO LOW TO INCLUDE IN THE PREVAILING TAF.  
HIGH AND MID CLOUDS TONIGHT WILL PREVENT SIGNIFICANT FOG AND LOW  
STRATUS FORMATION.  
 

 
   
MARINE
 
 
WEAK HIGH PRESSURE WILL BUILD EAST OF NORTH FLORIDA TOADY, THEN  
HIGH PRESSURE WILL STRENGTHEN AND PERSIST NORTH OF THE AREA  
THROUGH THE WEEKEND. THIS PATTERN WILL BRING AN EXTENDED PERIOD OF  
ONSHORE FLOW, WHICH WILL INCREASE EARLY NEXT WEEK AS THE PRESSURE  
GRADIENT STRENGTHENS BETWEEN THE HIGH PRESSURE RIDGE AXIS ACROSS  
THE GULF COAST REGION AND HURRICANE MARIA TRACKING NORTHWARD,  
SOMEWHERE BETWEEN 400-600 MILES EAST OF THE LOCAL COASTLINE SUN-  
MON. THE COMBINATION OF PERSISTENT ONSHORE FLOW AND SWELLS FROM  
DISTANT TROPICAL STORM JOSE AND HURRICANE MARIA WILL BRING AN  
EXTENDED PERIOD OF ELEVATED SEAS WITHIN THE LOCAL ATLANTIC WATERS  
WITH EXERCISE CAUTION CONDITIONS HEADLINED TONIGHT, POTENTIALLY  
THROUGH THURSDAY. SWELLS FROM MARIA ENTER THE LOCAL WATERS LATE  
THURSDAY OR FRIDAY WITH LOCAL SEAS BUILDING TO ADVISORY LEVELS  
THIS WEEKEND.  
 
RIP CURRENTS: BUILDING SWELLS AND ONSHORE FLOW WILL CONTINUE AN  
ELEVATED RIP CURRENT RISK WITHIN THE LOCAL WATERS THROUGH THE  
WEEKEND. A MODERATE RISK OF RIP CURRENTS IS EXPECTED BOTH TODAY  
AND AGAIN ON THURSDAY.  
 

 
   
HYDROLOGY
 
 
EXTENDED THE COASTAL FLOOD ADVISORY FOR THE ST. JOHNS RIVER BASIN  
AND ITS TRIBUTARIES DUE TO MINOR TO JUST SHY OF MODERATE FLOODING  
AROUND HIGH TIDE THROUGH THURSDAY EVENING. MODERATE RIVER  
FLOODING CONTINUED ALONG THE SANTE FE, ST. MARYS AND OCKLAWAHA  
RIVERS IN NORTHEAST FLORIDA WITH MINOR FLOODING ALONG THE SATILLA  
RIVER IN SOUTHEAST GEORGIA.  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
AMG 91 69 91 69 / 30 20 40 10  
SSI 87 73 87 74 / 20 10 0 10  
JAX 91 71 89 72 / 20 10 10 10  
SGJ 88 73 87 74 / 10 0 0 10  
GNV 91 69 90 69 / 10 10 20 10  
OCF 92 68 91 70 / 10 10 20 10  
 

 
   
JAX WATCHES/WARNINGS/ADVISORIES
 
 
FL...COASTAL FLOOD ADVISORY UNTIL 8 PM EDT THURSDAY FOR CLAY-COASTAL  
DUVAL-FLAGLER-INLAND DUVAL-PUTNAM-ST. JOHNS.  
 
GA...NONE.  
AM...NONE.  

 
 

 
 
ENYEDI/STRUBLE/WALKER  
 
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