National Weather Service Raw Text Product

538 
FXUS62 KJAX 181915
AFDJAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSONVILLE FL
210 PM EST TUE DEC 18 2012

.CURRENTLY...WEST TO NORTHWEST WINDS AND CLEAR SKIES ACROSS THE CWA 
WITH TEMPS IN THE UPPER 60S TO THE MID 70S. WINDS AROUND 15G25 MPH 
NOTED IN THE OBS TODAY AND EXPECT A DECREASE BY LATE AFTN AS SFC 
HIGH PRES EDGES CLOSER TO THE FORECAST AREA. A MID LEVEL TROUGH IS 
CONTINUE TO MOVE DOWNSTREAM WITH AXIS ALONG THE E COAST THIS AFTN.

.SHORT TERM...WED-FRI.
TONIGHT...CLEAR SKIES AND NEAR CALM WINDS WILL PROMOTE GOOD 
RADIATIONAL COOLING AND WITH EXPECTED MIN TEMPS SLIGHTLY UNDER 
CURRENT GUIDANCE. PATCHY FROST OVER THE WRN ZONES LOOKS POSSIBLE 
WITH THE CLEAR SKIES THOUGH DEWPOINTS MAY REMAIN JUST ABOVE FREEZING 
SO FROST POSSIBILITY DOES NOT LOOK LIKELY ATTM. MID 30S LOWS EXPECTED 
FOR MOST INLAND AREAS WITH LOWER TO MID 40S ELSEWHERE AND NEAR THE 
COAST WHERE ~3-5 MPH DRAINAGE FLOW WILL BE MORE LIKELY.  

WED...AFTER A COOL START...TEMPS WILL RISE UP TO THE LOWER TO MID 
70S AGAIN BUT WITH LESS WIND AND CONTINUED CLEAR SKIES. THE SFC HIGH 
PRES WILL EDGE EWD AND OFF THE NE FL COAST IN THE AFTN WITH A WEAK 
LLVL FLOW VEERING. WED NIGHT...SFC HIGH PRES WILL SHIFT WELL 
OFFSHORE WITH FLOW VEERING AHEAD OF NEXT FRONTAL SYSTEM. NOT AS 
CHILLY WITH DEEP LAYER FLOW BECOMING S TO SW ALL LEVELS THOUGH STILL 
MOSTLY CLEAR SKIES. 

THU...A STRONG COLD FRONT WILL BE MARCHING EWD TOWARD THE SE STATES 
WITH THE PARENT LOW PRES WELL N OVER THE OHIO VALLEY TO THE GREAT 
LAKES. OUR AIRMASS WILL START OUT VERY DRY WITH PWATS OF LESS THAN 1 
INCH...BUT STRONG LLVL FLOW FROM THE S AND SW WILL PUSH OUR 
DEWPOINTS TO THE LOWER 60S BASED ON SREF GUIDANCE. GFS PWATS 
INCREASE TO 1.5 TO POSSIBLY 2 INCHES AS ASSOCD PLUME OF MOISTURE 
HEAD OF THE STRONG COLD FRONT MOVES IN. AN 850 MB LLVL JET AROUND 
40-55 KT NOTED IN SREF AND GFS BUT LIMITING FACTOR TO ANY SEVERE WX 
THREAT (SPC OUTLOOKS SLIGHT RISK OF SEVERE STORMS MOST OUR CWA) WILL 
BE AMOUNT OF INSTABILITY. GIVEN THE MODEL SOUNDINGS AND SREF 
OUTPUT...MUCAPES LOOK TO BE ABOUT 200-400 J/KG AND A SUBSIDENCE 
INVERSION MAY BE SLOW TO ERODE AROUND 4500-5000 FT. THUS THIS WILL 
NOT BE A WIDESPREAD SEVERE EVENT BUT GUSTY WINDS ARE EXPECTED AHEAD 
OF THE FRONT ASSOCD WITH DAYTIME MIXING AND ALSO WITH SHALLOW 
CONVECTIVE SHOWERS AND ISOLD TO SCT THUNDERSTORMS ACCOMPANYING THE 
FRONT. 

THU NIGHT...FRONT WILL CONT TO PUSH EWD AND THEN S OF THE AREA BY 
EARLY FRI MORNING WITH SKIES CLEARING AND COOLER TEMPS. HIGHS POPS 
IN THE EVENING WILL ANTICIPATED DECREASING TO LESS THAN 15% 
LATE IN THE NIGHT BASED ON MODEL CONSENSUS. FRI TO FRI NIGHT...MUCH 
COOLER TEMPS AND CLEAR SKIES EXPECTED. A FREEZE LOOKS LIKELY BY SAT 
MORNING MOST ZONES WITH LOWS IN THE LOWER 30S WITH A FEW UPPER 20S 
POSSIBLE.


.LONG TERM...SAT-TUE.
A DRY AND COOL AIRMASS IS EXPECTED DURING THE WEEKEND WITH NEAR ZONAL 
FLOW ALOFT AND SFC HIGH PRES IN THE LOW LEVELS. WEAK WINDS VEER ON 
MON AHEAD OF NEXT FRONTAL SYSTEM WHICH APPEARS TO BECOME 
QUASI-STATIONARY ACROSS THE CAROLINAS TO LA TO ERN TX. TEMPS 
INCREASE MON AND TUE AND POPS WILL APPEAR TO REMAIN LOW ACROSS OUR 
CWA AS BEST MOISTURE AND LIFT WILL REMAIN TO THE N.  

&&

.AVIATION...CONDITIONS WILL BE VFR WITH WINDS DIMINISHING.

&&

.MARINE...WILL LET THE ADVISORY OFFSHORE EXPIRE AT 4 PM AND 
REPLACE WITH AN EXERCISE CAUTION FOR TONIGHT. MUCH LIGHTER
WINDS FOR WEDNESDAY AS HIGH PRESSURE MOVES IN OVER THE WATERS
AND NO HEADLINES EXPECTED. A STRONG COLD FRONT WILL PUSH THROUGH 
THE WATERS THURSDAY NIGHT. SMALL CRAFT ADVISORY CONDITIONS ARE LIKELY 
OFFSHORE THURSDAY AS SOUTH WINDS INCREASE IN ADVANCE OF THE FRONT...
AND THEN FOR ALL LEGS BEHIND THE FRONT THURSDAY NIGHT AND FRIDAY.
GUSTS TO GALE FORCE WILL BE POSSIBLE OFFSHORE THURSDAY NIGHT AND FRIDAY.

&&
            
.FIRE WX...RELATIVE HUMIDITY VALUES WILL DROP BELOW CRITICAL 
THRESHOLDS OVER NORTHEAST FLORIDA WEDNESDAY. WINDS WILL BE MUCH 
LIGHTER ON WEDNESDAY SO NO RED FLAG IS EXPECTED. MUCH COOLER 
AND DRIER WILL USHER INTO THE AREA BEHIND A STRONG COLD FRONT FRIDAY.      
SOUTH WINDS WILL INCREASE TO 15 MPH ON FRIDAY AND THEN WINDS WILL 
SHIFT TO NORTHWEST 15 MPH BEHIND THE FRONT ON FRIDAY. MIN RH'S 
WILL BE WELL ABOVE CRITICAL VALUES IN ADVANCE OF THE FRONT ON
THURSDAY AND THEN FALL TO NEAR CRITICAL VALUES ON FRIDAY WHICH MAY 
NECESSITATE A RED FLAG DUE TO THE WIND. MIN RH'S WILL FALL TO 
BELOW CRITICAL VALUES OVER THE WEEKEND BUT WINDS WILL BE LESS 
THAN 15 MPH.     

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  36  73  44  75 /   0   0  10  60 
SSI  48  68  53  75 /   0   0   0  60 
JAX  38  72  49  81 /   0   0   0  60 
SGJ  46  71  54  79 /   0   0   0  50 
GNV  39  75  47  79 /   0   0   0  70 
OCF  40  76  50  80 /   0   0   0  60 

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GA...NONE.
AM...SMALL CRAFT ADVISORY FOR WINDS UNTIL 4 PM EST THIS AFTERNOON 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-ST AUGUSTINE TO FLAGLER BEACH FL 20 NM TO 60 NM 
     OFFSHORE.

&&

$$

SHASHY/PETERSON/MCALLISTER