FXUS62 KJAX 011519
AFDJAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSONVILLE FL
1019 AM EST TUE DEC 1 2009
...THREAT OF SEVERE WEATHER WEDNESDAY AFTERNOON AND EVENING...
.PUBLIC UPDATE...SURFACE COLD FRONT HAS LIKELY REACHED NORTH-CENTRAL
FLORIDA...ALTHOUGH FAVORABLE CONDITIONS FOR ISENTROPIC LIFT HAVE
ESTABLISHED ACROSS NORTHEAST FLORIDA AS WELL AS AREAS SOUTH OF U.S.
HIGHWAY 82 IN SOUTHEAST GEORGIA...RESULTING IN CONSIDERABLE LOW
CLOUDS. NUMERICAL MODELS ARE IN AGREEMENT THESE LOW CLOUDS WILL
SPREAD FARTHER NORTH ACROSS SOUTHEAST GEORGIA THIS AFTERNOON. SURFACE
FRONTAL BOUNDARY IS FORECAST TO BEGIN LIFTING NORTH AS A WARM FRONT
THIS AFTERNOON...AFFECTING PORTIONS OF NORTHEAST FLORIDA. ATTENDANT
LIFT WILL LIKELY GENERATE ISOLATED TO SCATTERED SHOWERS THIS
AFTERNOON ACROSS NORTHEAST FLORIDA. ADDITIONALLY...THE FIRST IN
SERIES OF MID-LEVEL DISTURBANCES PRECEDING STORM SYSTEM WILL TRAVERSE
OUR WESTERN ZONES THIS AFTERNOON...AND THERE IS THE POTENTIAL FOR A
FEW SHOWERS TO ACCOMPANY THIS FEATURE. RAIN PROBABILITIES LOOK
REASONABLE FOR TODAY. HAVE INCREASED WIND SPEEDS FOR OUR COASTAL
ZONES...RESULTING IN BREEZY WORDING. GUSTS TO 20 TO 25 MPH WILL BE
POSSIBLE NEAR THE COAST...ESPECIALLY POINTS NORTH OF ST. AUGUSTINE.
&&
.AVIATION...ALTHOUGH FRONTAL BOUNDARY HAS REACHED NORTH-CENTRAL
FLORIDA...THIS FEATURE IS FORECAST TO BEGIN LIFTING NORTHWARD AS A
WARM FRONT LATER TODAY. THE INTERACTION OF THIS FEATURE COUPLED
WITH FAVORABLE ISENTROPIC LIFT EXTENDING NORTH OF THIS FEATURE
WILL LIKELY MAINTAIN MVFR CEILINGS FOR NORTHEAST FLORIDA
TERMINALS FOR MUCH OF THIS TAF CYCLE...WITH MVFR CEILINGS
LIKELY SPREADING NORTH TO IMPACT KSSI TERMINAL BY AROUND 17Z.
&&
.MARINE...COLD FRONT HAS NOW REACHED NORTH-CENTRAL FLORIDA AND
ADJACENT WATERS...WITH NE WINDS INCREASING OVER OUR LOCAL WATERS.
WILL CONTINUE TO ADVERTISE SCEC HEADLINES FOR OUR NEARSHORE LEGS...
WITH SCA HEADLINES FOR OUR OFFSHORE LEGS. THERE IS STILL SOME
UNCERTAINLY WITH EVOLUTION OF LOW TO OUR WEST...AND MAY NEED TO
EXTEND/EXPAND SCA HEADLINES. WILL MAKE NECESSARY ADJUSTMENTS WITH
AFTERNOON PACKAGE AFTER ANALYZING 12Z GUIDANCE.
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GA...NONE.
AM...SMALL CRAFT ADVISORY UNTIL 5 AM EST WEDNESDAY 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.
&&
.PREVIOUS PUBLIC...
SHORT TERM...COMPLEX WX FORECAST SETTING UP DURING THE NEXT 48
HOURS. WEAK COLD FRONT WILL STALL JUST S OF THE AREA TODAY BEFORE
LIFTING BACK N AS A WARM FRONT TONIGHT. INCREASING ISENTROPIC LIFT
LATE TODAY AND ESPECIALLY TONIGHT WILL ALLOW MOSTLY STRATIFORM
RAINS TO DEVELOP ACROSS THE AREA BEFORE LIFTING N. HEAVIEST RAINS
WILL LIKELY OCCUR N OF OUR AREA WHILE RAINS OVER THE S BECOME A
BIT MORE ISOLATED AND SHOWERY. WARM AIR ADVECTION WILL INCREASE
RAPIDLY OVERNIGHT...WITH TEMPERATURES OVER FL ZONES ONLY FALLING A
FEW DEGREES AFTER SUNSET AND LIKELY BEGINNING TO RISE AFTER
MIDNIGHT.
SQUALL LINE WILL BEGIN TO ORGANIZE WELL W OF THE AREA TONIGHT AS
STORM SYSTEM BEGINS TO SHIFT E AND THEN NE. TIMING OF INCREASING
UPPER JET DYNAMICS AND LOW LEVEL WIND FIELD APPEARS TO FAVOR
CONTINUATION OF SQUALL LINE ACROSS OUR AREA FROM LATE AFTERNOON
WED THRU JUST AFTER MIDNIGHT. THERE ARE DISCREPANCIES WITH THE
TIMING OF THE PRECIP FIELD...THE GFS IS THE FASTEST WITH THE NAM
JUST A BIT SLOWER AND THE ECMWF THE SLOWEST OF ALL. THE GFS
ENSEMBLE MEAN IS IN CLOSE AGREEMENT WITH THE OPERATIONAL GFS...
AND PRECIP ASSOCIATED WITH VERY DYNAMIC SYSTEMS TEND TO SWEEP
ACROSS THE AREA FAIRLY QUICKLY. AS A RESULT...HAVE LEANED TOWARD
THE NAM SINCE IT IS A COMPROMISE BETWEEN THE OTHER GUIDANCE SUITES
LEANING TOWARD THE FAST SIDE.
WILL CONTINUE TO MENTION THE THREAT OF SEVERE WX...MAINLY FROM
STRAIGHT LINE WINDS. THE LOW-LEVEL JET WILL BE AROUND 60 KTS
DURING THE AFTERNOON AND EVENING HOURS...AND EVEN HEAVY SHOWERS
MAY BE ABLE TO MIX DOWN SWA CRITERIA WIND GUSTS. MAY BE PARTLY
CLOUDY SKIES OVER AT LEAST THE FL PORTION OF THE AREA WED MORNING
BEFORE MID AND HIGH CLOUDS INCREASE FROM THE W. THIS...ALONG WITH
STRONG WARM AIR ADVECTION...SHOULD ALLOW FOR DESTABILIZATION OF
THE AIRMASS...ENUF FOR 300-800 J/KG CAPES TO BE REALIZED. THIS
WILL ESPECIALLY BE TRUE ACROSS NE FL. MAY BE SOME DISCRETE STRONG
TO SEVERE CELLS OUT AHEAD OF THE MAIN SQUALL LINE AS WELL. WITH
MODEST CAPES AND INCREASED HELICITIES...ISOLATED TORNADOES ARE NOT
OUT OF THE QUESTION. SPC HAS A 30 PERCENT COMBINED SEVERE THREAT
AREA OVER US FOR WED. THE NAM...AND TO A LESSER EXTENT THE
GFS...DO INDICATE AN AREA OF CONVECTIVE INHIBITION OVER MUCH OF
THE AREA THRU THE MORNING HOURS AND PERHAPS EXTENDING INTO THE
AFTERNOON ON WED. THIS MAY LIMIT THE SEVERE THREAT AND WILL NEED
TO BE ASSESSED AS THE EVENT DRAWS CLOSER.
LONG TERM...BIGGEST CHANGE TO THE EXTENDED PACKAGE IS THE DEVELOPMENT
OF DISTURBANCES OVER THE GOMEX BY THE WEEKEND WHICH MOVE ALONG THE
STALLED FRONTAL BOUNDARY S OF THE AREA. THIS IS CONSISTENT WITH AN EL
NINO PATTERN. IN ADDITION...THE ECMWF IS IN AGREEMENT WITH THIS
SOLUTION. AS A RESULT...INCREASING CLOUDS AND PRECIP ARE FORECAST TO
OCCUR FRI NIGHT AND SAT...PARTICULARLY OVER NE FL. THIS WILL KEEP
TEMPERATURES WARMER AT NIGHT AS WELL...WITH TEMPERATURES POSSIBLY
REMAINING IN THE 40S ACROSS THE SE 1/2 OF THE AREA. HAVE TWEAKED THE
EXTENDED PACKAGE IN THIS DIRECTION.
&&
$$
ECZ
