218  
FXUS62 KJAX 200910  
AFDJAX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE JACKSONVILLE FL  
410 AM EST MON NOV 20 2017  
   
CURRENTLY
 
A 1025 MB HIGH PRESSURE RIDGE WAS LOCATED FROM THE TN  
VALLEY TO THE LOWER MS VALLEY WITH A NORTHERLY LOW LEVEL FLOW OVER  
THE FORECAST REGION. THE MUCH COOLER AIRMASS THAT MOVED IN EARLY  
SUNDAY HAS RESULTED IN CHILLY TEMPS EARLY THIS MORNING WITH THE  
COOLEST READINGS FROM SOME NON-NWS INLAND STATIONS WEST OF HIGHWAY  
301 NORTH I-10 AROUND 33-35 DEG AT 3 AM. IN THESE AREAS WINDS ARE  
LIGHT TO CALM SO IT IS VERY POSSIBLE SOME PATCHY FROST MAY FORM IN  
THESE CONDITIONS OVER THE INLAND AREAS. OVER COASTAL AREAS TIGHTER  
PRES GRADIENT IS CAUSING WINDS TO STAY IN THE 5-10 KT RANGE WHERE  
TEMPS ARE STILL ABOUT 50 DEG. FLOW IS MAINLY ZONAL ALOFT WITH ONE  
MID LEVEL TROUGH LIFTING OUT TO THE NORTHEAST AND AN UPPER LEVEL JET  
OFF THE EAST COAST GENERATING SOME SCT-BROKEN CIRRUS LOCALLY...  
OTHERWISE CLEAR SKIES.  
   
NEAR TERM.../TODAY-TONIGHT/
 
 
WEAK MID LEVEL RIDGE OVER THE AREA EARLY THIS PERIOD WILL MOVE EAST  
QUICKLY AS MID-UPPER LEVEL TROUGH AMPLIFIES ACROSS THE NRN GULF  
OF MEXICO. SFC HIGH PRESSURE OVER THE LOWER CONUS WILL QUICKLY MOVE  
EAST AND OFFSHORE EARLY TUESDAY MORNING. THIS WILL RESULT IN A  
WARMING TREND DURING THIS PERIOD AND INCREASING LOW TO MID  
LEVEL MOISTURE.  
 
FOR TODAY...A CHILLY START WITH WIND CHILLS STARTING OUT IN THE MID-  
UPPER 30S INLAND AND LOWER 40S NEAR THE COAST. LOW LEVEL FLOW  
WILL TURN NORTHEAST TO EAST DURING THE DAY WITH BREEZY CONDITIONS  
ALONG THE COAST AS THE SFC HIGH SCOOTS TO NC AND SUPPORT ~15G20 MPH  
AT TIMES ALONG THE COAST. INCREASING STRATOCU/CUMULUS CLOUDS  
EXPECTED TODAY MAINLY EASTERN ZONES. A COUPLE OF MODELS ACTUALLY  
PUTTING IN LIGHT QPF NEAR THE COAST THOUGH THIS IS LIKELY  
OVERDONE...AT MOST A FEW SPRINKLES POSSIBLE. HIGHS TODAY  
FORECAST IN THE MID 60S TO AROUND 70.  
 
TONIGHT...FAIRLY DECENT MODEL AGREEMENT OF MOSTLY CLOUDY SKIES  
DEVELOPING TONIGHT AS LOW-MID LEVEL FLOW VEERS MARKEDLY. WARM  
ADVECTION AND ISENTROPIC ASCENT SHOULD ONLY GET STRONGER OVERNIGHT  
SO MODEL SOLUTIONS APPEAR REASONABLE. MODELS ALSO FAIRLY CONSISTENT  
ALONG WITH PRIOR FORECAST OF A FEW LIGHT SHOWERS POSSIBLE  
ALONG THE COAST AFTER MIDNIGHT AND WILL RETAIN THIS FOR NOW. COULD  
BE SOME LIGHT FOG INLAND BUT TOO LIMITED LOW LEVEL MOISTURE PER NAM  
SOUNDINGS. LOWS TONIGHT WILL BE WARMER THAN THIS MORNING WITH MINS  
FROM ABOUT 45 TO 50 INLAND AND MID 50S TO NEAR 60 NEARER THE COAST.  
   
SHORT TERM (TUESDAY-WEDNESDAY NIGHT)
 
 
HIGH PRESSURE RAPIDLY MOVES MOVES OFFSHORE AS A SHORT WAVE TROUGH  
APPROACHES THE AREA. THE RETURN FLOW WILL BRING IN MILDER TEMPS WITH  
AN INCREASE IN MOISTURE. A WEAK SURFACE LOW FORMS AND MOVES ALONG  
THE WEST FL GULF COAST ON TUESDAY BEFORE RE-DEVELOPING OFFSHORE THE  
CAROLINAS LATE TUESDAY NIGHT. ISENTROPIC LIFT...CONVERGENCE...AND  
LARGE SCALE ASCENT FROM THE TROUGH WILL LEAD TO A GOOD CHANCE OF  
RAIN WITH LOCALLY HEAVY RAIN POSSIBLE ESPECIALLY SOUTH OF THE I-10  
CORRIDOR WHERE 1 TO 2 INCHES IS POSSIBLE. MODEL SOUNDINGS INDICATE  
THERE MAY BE ENOUGH INSTABILITY FOR A FEW ELEVATED STORMS ACROSS THE  
SAME AREA. PCP WILL TAPER OFF BY LATE TUESDAY NIGHT WITH A BRIEF  
LULL EARLY WED AS THE SHORT WAVE LIFTS OUT OF THE AREA. ANOTHER MORE  
POTENT SOUTHERN STREAM SHORT WAVE TROUGH WILL BEGIN TO DROP  
SOUTHEAST ACROSS THE SOUTHEAST U.S. AND GULF OF MEXICO WED NIGHT  
WITH CYCLOGENESIS EITHER IN THE CNTL OR SOUTHERN GULF OF MEXICO  
WHICH WILL BRING ANOTHER GOOD CHANCE OF RAIN ESPECIALLY ACROSS THE  
FL PENINSULA.  
   
LONG TERM (THURSDAY-SUNDAY)
 
 
THERE CONTINUES TO BE DIFFERENCES BETWEEN THE ECMWF AND GFS ON THE  
EVOLUTION OF A POTENT SOUTHERN STREAM MID/UPPER TROUGH THAT WILL BE  
TRAVERSING THE AREA AND WITH RESULTING CYCLOGENESIS ACROSS FLORIDA.  
THE ECMWF IS SLOWER AND MORE POTENT WHICH RESULTS IN A PROLONGED  
PERIOD OF RAIN FROM THANKSGIVING INTO FRIDAY NIGHT WHEREAS THE GFS  
IS FASTER AND HAS THE SYSTEM BEGINNING TO CLEAR THE AREA DURING THE  
DAY FRIDAY. BOTH MODELS SUGGEST A GOOD CHANCE OF RAIN ESPECIALLY  
ACROSS THE FL PENINSULA ON THANKSGIVING. WILL TAKE A BLEND OF THE  
GUIDANCE AND HAVE LINGERING SHOWERS ACROSS THE EASTERN HALF OF THE  
AREA WITH CLEARING FROM WEST TO EAST IN THE AFTERNOON. LOCALLY HEAVY  
RAIN IS POSSIBLE ESPECIALLY ON THANKSGIVING DAY ALTHOUGH EXACT  
AMOUNTS WILL DEPEND ON EXACT TRACK AND STRENGTH OF THE LOW. DUE TO  
CLOUD COVER/PCP AND WARM SECTOR SOUTH OF THE AREA...MAX TEMPS HELD  
TO BELOW NORMAL. CONFIDENCE CONTINUES LOW ON THUNDER GIVEN THE LACK  
OF INSTABILITY AND BEING IN COOL SECTOR ALTHOUGH A FEW ELEVATED  
STORMS POSSIBLE ACROSS THE FAR SOUTH. THE LONG WAVE TROUGH WILL MOVE  
EAST OF THE REGION OVER THE WEEKEND WITH HIGH PRESSURE GRADUALLY  
BUILDING IN FROM THE GULF COAST. EXPECTING OVERALL A DECREASE IN  
CLOUDS BY LATE FRIDAY WITH MOSTLY CLEAR CONDITIONS OVER THE WEEKEND  
WITH MAX TEMPS GENERALLY IN THE 60S TO NEAR 70 LOWS MOSTLY IN THE  
40S.  
 

 
   
AVIATION
 
VFR WILL PREVAIL THOUGH INCREASING LOW LEVEL CLOUDS  
EXPECTED TODAY AND TONIGHT. HAVE CONTINUED TO BRING IN SCT-LCL  
BROKEN CLOUDS AROUND 3000-4000 FT LATER TODAY THROUGH TONIGHT AS  
ONSHORE FLOW AND WARMING AND MOISTENING TREND IS EXPECTED. WILL HAVE  
TO MONITOR GUIDANCE AND SATELLITE IMAGERY FOR POSSIBLE INCLUDING  
OCCASIONAL MVFR CIGS FOR ALL TAFS EXCEPT FOR GNV AFTER 18Z AS THERE  
IS SUPPORT FROM GFS, RAP AND SREF GUIDANCE FOR CIGS AROUND 2500-3500  
FT BUT TIMING AND PROBABILITIES ARE UNCERTAIN. WINDS TODAY WILL  
TRANSITION FROM NORTHERLY THIS MORNING TO NORTHEAST AND EAST DURING  
THE DAY AT 10-15 KT. LIGHTER WINDS EXPECTED TONIGHT.  
 

 
   
MARINE
 
 
NORTHEAST TO EAST FLOW TODAY AROUND 15-20 KT AND SEAS OF UP TO 4-6  
FT SO SCEC HEADLINE WILL BE IN EFFECT. A WARM FRONT WILL MOVE TOWARD  
THE AREA TUESDAY CAUSING WINDS TO TURN MORE SOUTHEAST WITH MORE  
VARIED FLOW TUESDAY NIGHT DUE TO SHOWERS AND A FEW STORMS. WINDS  
TURN MORE NORTHERLY WED AS ONE IN A SERIES OF LOWS MOVES OFFSHORE OF  
THE FL EAST COAST. ANOTHER SFC LOW APPROACHES FROM THE SOUTH  
THURSDAY THEN MOVES OFFSHORE BY LATE WEEK BUT TIMING UNCERTAIN DUE  
TO MODEL DISAGREEMENT. SCEC OR SCA HEADLINES POSSIBLE THROUGH MOST  
OF THE WEEK DUE TO THE ELEVATED WINDS AND SEAS...BUT BEST CHANCES  
WILL BE IN THE OFFSHORE ZONES.  
 
RIP CURRENTS: AN ONSHORE FLOW AND ROUGH SEAS WILL RESULT IN  
MODERATE RISK OF RIP CURRENTS TODAY AND TUESDAY.  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
AMG 65 48 70 51 / 0 10 40 40  
SSI 65 58 71 58 / 0 20 60 50  
JAX 68 53 73 55 / 0 10 60 50  
SGJ 68 61 73 59 / 10 20 60 50  
GNV 71 53 72 54 / 0 10 60 40  
OCF 73 55 74 56 / 0 10 60 40  
 

 
   
JAX WATCHES/WARNINGS/ADVISORIES
 
 
FL...NONE.  
GA...NONE.  
AM...NONE.  
 

 
 

 
 
SHASHY/PETERSON  
 
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