FXUS62 KJAX 300644
AFDJAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSONVILLE FL
145 AM EST MON NOV 30 2009

...INCREASING THREAT OF SEVERE WEATHER WEDNESDAY...

.SHORT TERM...LATEST MSAS ANALYSIS SHOWS HIGH PRESSURE WHICH HAS
BEEN A MAINSTAY THE LAST SEVERAL DAYS CONTINUES TO INFLUENCE OUR
REGION TONIGHT. RIDGE AXIS NOW RESIDES OVER THE CENTRAL PENINSULA
WITH SEVERAL SMALL BUBBLE HIGHS DEVELOPING OVER NORTHEAST FLORIDA.
LIMITED CIRRUS ALONG THE INTERSTATE 10 CORRIDOR IS ALLOWING FOR
OPTIMUM RADIATIONAL COOLING CONDITIONS AND HAVE SEEN TEMPS DROP
MUCH FASTER THAN MODEL PROJECTIONS. THIS HAS RESULTED IN SHALLOW
BUT DENSE FOG AT SOME OBS SITES ALONG THE EAST COAST AND WILL NEED
TO INCLUDE IN THE UPDATED INITIALIZED GRID SET.

FOR THE FIRST 24 HOURS OF THE FORECAST...THE CWA WILL CONTINUE TO
BE INFLUENCED BY THE NORTHERN STREAM PRIMARILY WITH A STRONG
SHORTWAVE DIVING THROUGH THE OHIO AND TENNESSEE VALLEYS. RESULTANT
FRONTAL BOUNDARY CURRENTLY RESIDES FROM KENTUCKY THROUGH NORTHERN
MISSISSIPPI WITH MODERATE LIGHTNING ACTIVITY NOTED. THE FRONT WILL
SLIDE SOUTHWARD THIS AFTERNOON WITH ALREADY SOME MODEL
DISCREPANCIES ENTERING THE PICTURE. NAM12 HAS HIGHER MOISTURE
CONTENT WITH THE FRONT AND MAINTAINS MORE LIFT INTO OUR AREA. THE
GFS EJECTS A MAJORITY OF THE ENERGY NORTH OF THE REGION AND OFF
THE CAROLINA COAST WITH A DECAYING FRONT IN ITS WAKE. GFS HAS BEEN
CONSISTENT WITH A WEAKER SOLUTION FOR QUITE A WHILE NOW AND WITH
SUPPORT FROM THE ECMWF...WILL RIDE OUT THE DRIER SOLUTION FOR NOW.

EXPECTING VERY LITTLE ACTIVITY ALONG THE STALLED FRONT ON TUE WITH
NORTHEAST FLOW ON COOL SIDE OF THE FRONT ALONG WITH ABUNDANT CLOUD
COVER NOT LETTING TEMPS GET OUT OF THE LOWER 60S.

CONFIDENCE IS INCREASING WITH EACH MODEL RUN THAT WE WILL GET
VERY LITTLE OUT OF THE WARM FRONT OF THIS SYSTEM AS BY THE TIME
BEST ISENTROPIC ASCENT ARRIVES...MOISTURE HAS LIFTED NORTH OF THE
AREA. REGARDLESS...THERE SHOULD BE A SHARP GRADIENT TO THE PRECIP
AND WOULD EXPECT ONLY FAR NW ZONES TO RECEIVE MEANINGFUL RAINFALL
WITH INITIAL PHASE OF THIS SYSTEM.

THE MAIN EVENT FOR OUR AREA LOOKS TO BE ASSOCIATED WITH THE SQUALL
LINE WED AFTERNOON AND INTO THE EVENING HOURS. SOME BIG
DIFFERENCES IN THE POSITION OF THE LOW AMONG THE NAM12...GFS...AND
ECMWF WILL GREATLY INFLUENCE THE MODE AND DEGREE OF SEVERE WEATHER
EXPECTED BUT TIMING OF THE FRONTAL BAND ITSELF IS LARGELY THE
SAME. NAM12 IS SLOWER BUT WILL GO WITH THE CONSENSUS AT THIS POINT
WHICH MAKES THIS A WED EVENT FOR US. UP UNTIL THE MAIN BAND MOVES
THROUGH...MODELS ARE INDICATING LESS IN THE WAY OF INHIBITION IN
PRE FRONTAL ENVIRONMENT THAN PREVIOUS RUNS AND MAY BE ABLE TO GET
SOME ISOLATED ACTIVITY GOING AFTER ALL. THERE WILL BE NO LOW LEVEL
WIND CORE AT THIS POINT...BUT HELICITIES WILL BE QUITE HIGH AND
WITH TEMPS REACHING THE 80S AND INSTABILITY INCREASING...COULD SEE
A FEW ROTATING STORMS IN THE EARLY AFTERNOON.

SO FOR THE SQUALL LINE ITSELF...LOOKS LIKE A CONSENSUS THAT AN 850
MB WIND CORE BETWEEN 55 AND 65 KNOTS WILL DEVELOP AND PUSH THROUGH
THE ENTIRE AREA. CAPES STILL LOOK BORDERLINE AT 500-750 J/KG BUT
UPPER DIFFLUENCE WILL CREATE INCREDIBLE LIFT WHICH COULD VERY WELL
OVERCOME THIS LACK OF INSTABILITY. ALSO OF NOTE IS HOW LOW IN THE
COLUMN SIGNIFICANT WINDS EXTEND. WOULD NOT BE SURPRISED TO SEE
DAMAGING ACTIVITY WITHIN JUST STRONG SHOWER ACTIVITY WITH THIS
SYSTEM. EVENTUAL LOW TRACK WILL BE CRITICAL IN DETERMINING TORNADO
THREAT BUT WILL BEGIN TO PLAY UP THE POSSIBILITIES IN HWO AND
GRAPHICAST. ACTIVITY WILL CLEAR VERY QUICKLY EARLY WED NIGHT WITH
WRAP AROUND MOISTURE NOW STAYING WELL NORTH OF THE AREA.

.LONG TERM...MUCH COLDER AIR BEHIND THE FRONT AS HIGH PRESSURE
BUILDS IN. NEW MEX HAS 30 FOR JAX ON SAT MORNING...BUT WILL STICK 
CLOSER TO THE ENSEMBLE NUMBERS FOR NOW AT 35.

&&

.AVIATION...AFTERNOON SEABREEZE ALONG THE ATLANTIC COAST HAS 
INTRODUCED ENUF LOW-LEVEL MOISTURE INTO THE ATMOSPHERE TO ALLOW 
SHALLOW BUT RATHER DENSE FOG TO DEVELOP AT A FEW OF THE COASTAL 
SITES. WILL CONTINUE TO SEE PATCHY FOG...SOME OF IT DENSE...
OVERNIGHT...PARTICULARLY IF HIGH CLOUDS CONTINUE TO STAY THIN OVER 
THE AREA. OTHERWISE...VFR CONDITIONS EXPECTED THRU THE NEXT 24 HOURS 
ALTHO SOME MVFR CIGS POSSIBLE NEAR THE FIRST FRONT MON NIGHT.

&&

.MARINE...WINDS ARE EXPECTED TO INCREASE TO AROUND SMALL CRAFT 
ADVISORY CRITERIA DURING THE DAY TUE AS WINDS VEER TO NE BEHIND 
FIRST FRONT. WILL HOLD OFF INSERTING THIS HEADLINE FOR NOW AS THERE 
IS SOME UNCERTAINTY AS TO WHETHER THE CRITERIA WILL BE MET BY THE 
3RD PERIOD. WINDS WILL CONTINUE TO VEER AND INCREASE AS LOW PRESSURE 
W OF THE AREA MOVES NE AND INCREASES PRESSURE GRADIENT. WILL LIKELY 
HAVE WINDS AROUND 30 KTS OUT OF THE S WITH GUSTS TO GALE FORCE. IT 
APPEARS THAT GUSTS WILL BE FREQUENT ENUF OVER THE OFFSHORE WATERS TO 
WARRANT GALE WARNINGS WED AFTERNOON AND EVENING...BUT STILL TOO 
EARLY TO INCLUDE HEADLINE. WILL FURTHER BEEF UP THE SYNOPSIS.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  73  46  65  51 /  10  20  10  50 
SSI  72  52  65  55 /   0  10  10  40 
JAX  74  51  67  57 /   0  20  20  30 
SGJ  74  55  69  61 /   0  20  20  30 
GNV  74  50  70  59 /   0  20  20  30 
OCF  75  52  71  60 /   0  20  20  30 

&&

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

&&

$$

DEESE/CARROLL