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980
FXUS62 KMLB 200853
AFDMLB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MELBOURNE FL
353 AM EST SAT DEC 20 2014

.DISCUSSION...

CURRENTLY...

...INCREASING CHANCE FOR SHOWERS/STORMS LATE SUNDAY INTO WED...

BROAD HI PRES RIDGE BLANKETING THE SW ATLC WITH A WEAK COLD FRONT
OVER THE GOMEX. EVENING SOUNDINGS SHOW INCREASING MOISTURE ACRS THE
PANHANDLE ASSOCD WITH THE FRONT WITH PWAT VALUES CREEPING ABV 1.0".
OVER CENTRAL FL...KTBW SOUNDING MEASURED PWATS ARND 0.8"...THOUGH
MOST OF THIS IS IN THE FORM OF A MID/UPR LVL DECK AS AVG DEWPOINT
DEPRESSIONS THRU THE H100-H70 LYR REMAIN BTWN 10-15C. TO THE S...
KMFL SHOWS SUBSTANTIAL DRY AIR THRU THE H85-H50 LYR. RUC ANALYSIS
INDICATES UPSTREAM H100-H70 MEAN RH VALUES INCREASING FROM 40PCT
OVER S FL TO AOA 80PCT OVER THE YUCATAN CHANNEL...AND H85-H50 VALUES
INCREASING FROM ARND 40PCT OVER CENTRAL FL TO AOA 60PCT OVER THE
CENTRAL GOMEX.

ALOFT...A 90-110KT JET STREAK EXTENDING FROM THE BAJA PENINSULA TO
BERMUDA HAS A STRONG ZONAL ORIENTATION THAT IS GENERATING A DEEP
W/SW FLOW THRU THE H85-H30 LYR. MODERATELY COOL AIR AIR IN PLACE
WITH H50 TEMPS ARND -10C. SIG VORT MAXES ARE ALMOST NONEXISTENT THRU
THE H85-H30 LYR...WHILE THE OMEGA FIELDS THRU THE SAME LYR ARE
BASICALLY NEUTRAL. H70-H50 LAPSE RATES ARND 6.0C/KM ARE NOT
ESPECIALLY IMPRESSIVE...ESPECIALLY GIVEN THE H85-H70 LAPSE RATES ARE
BLO 5.0C/KM.

TODAY-TONIGHT...
THE RIDGE AXIS WILL BE THE PRIMARY WX FEATURE FOR CENTRAL FL AS THE
JET OVER THE SRN TIER STATES DRAGS THE WEAK COLD FRONT INTO THE FL
PANHANDLE. HOWEVER...THE ZONAL ORIENTATION OF THE JET WILL PREVENT
THE FRONT FROM PUSHING MUCH FURTHER S THAN THE NECK OF THE PENINSULA
BY DAYBREAK SUN.

RUC40 ANALYSIS SHOWS A TIGHT ISENTROPIC GRADIENT THRU THE 300K-315K
LYR THAT WILL EVENTUALLY SET THE STAGE FOR THE NEXT RAIN EVENT ACRS
CENTRAL FL AS THE MID LVL WINDS REMAIN OUT OF THE W/SW. HOWEVER...
THE DRY AIR OVER THE CENTRAL/SRN PENINSULA WILL NEED TO MODIFY
BEFORE ANY MEASURABLE PRECIP OCCURS...ESPECIALLY GIVEN THE LACK OF
ANY SIG DYNAMIC/THERMODYNAMIC SUPPORT.

FORECAST WILL REMAIN DRY. TEMPS WILL BE A FEW DEG WARMER THAN FRI
DUE TO WARM AIR ADVECTION THAT WILL ACCOMPANY THE S/SW FLOW THAT HAS
DVLPD THRU THE H100-H85 LYR. AFTN MAXES IN THE M/U70S WILL BE 3-7F
DEG ABV AVG. OVERNIGHT MINS IN THE M/U50S EXCEPT L60S ALONG THE
IMMEDIATE COAST...5-10F ABV AVG.

SUN-WED...MODELS CONTINUE TO SHOW A QUITE CLOUDY PERIOD WITH
DAILY RAIN CHANCES.

SUN-MON...A TROUGH WITH FAIRLY DECENT SOUTHERN EXTENT INTO THE
WESTERN GULF ON SUNDAY WILL DAMPEN OUT AS IT MOVES ACROSS THE
SOUTHEAST STATES SUNDAY NIGHT/MON. THERE WILL INITIALLY BE A MID
LEVEL DRY LAYER SUNDAY BUT INCREASING SOUTH/SOUTHWEST FLOW IN THE
LOW/MID LEVELS WILL MOISTEN UP THE ATMOSPHERE CONSIDERABLY BY LATE
DAY AND SUNDAY NIGHT. GFS/ECMWF DIFFER A BIT WITH HIGHEST PRECIP
COVERAGE. THE GFS SHOWS HIGH POPS AREAWIDE SUNDAY NIGHT INTO MON.
THE ECMWF CONCENTRATES THE HIGHEST COVERAGE ACROSS NORTHERN
SECTIONS...WHICH IS MORE TYPICAL FOR THIS TIME OF THE YEAR AND
WHERE THE GREATEST ISENTROPIC LIFT IS SHOWN. THEREFORE HAVE NOT
GONE WITH THE 60-70 POPS INDICATED BY THE GFS...EXCEPT ACROSS THE
FAR NORTH.  THINK THAT PRECIP WILL MAINLY BE SHOWERY BUT CANNOT
RULE OUT SOME ELEVATED INSTABILITY AND ISOLATED THUNDER.

TUE-WED...THE MODELS ONLY SHOW SLIGHT CHANGES WITH THE NEXT
TROUGH WHICH WILL BE HIGHLY AMPLIFIED AND DIG WELL INTO THE GULF
OF MEXICO. A PRE FRONTAL BAND OF SHOWERS/STORMS IS EXPECTED TO
PUSH INTO NORTHERN SECTIONS TUE NIGHT AND SOUTHERN SECTIONS WED.
THIS IS SLIGHTLY SLOWER THAN PREVIOUS THINKING. THE DEEPENING
SURFACE LOW ASSOCIATED WITH THIS SYSTEM WILL BE LIFTING INTO THE
OHIO VALLEY AS THE BAND OF CONVECTION REACHES THE LOCAL AREA.
STILL THE LOW LEVEL WIND FIELDS ARE PROGGED TO BE 40-45 KNOTS. SO
FAST MOVING STORMS ARE EXPECTED WHICH MAY BRING A CHANCE FOR
DAMAGING WIND GUSTS.

HAVE GONE WITH CHANCE POPS ON TUE DUE TO THE MOIST SOUTHERLY FLOW
AND KEPT MENTION OF THUNDER DUE TO A POTENTIAL FOR SOME
DIVERGENCE ALOFT IN THE PRESENCE OF MODEST SURFACE HEATING.
GREATEST DYNAMICS ARE INDICATED TUE NIGHT INTO WED SO HAVE GONE
WITH A PERIOD OF LIKELY POPS FOR THE ENTIRE AREA THEN.

CHRISTMAS THRU NEXT SAT...
COOL/DRY AIR ADVECTION INDICATED ON CHRISTMAS DAY. MORNING LOWS IN
THE UPPER 40S TO LOWER 50S EXPECTED WITH DAYTIME HIGHS IN THE
LOWER TO MID 60S. HIGH PRESSURE RIDGE OVER THE AREA ON FRI WILL
CONTINUE THE DRY WEATHER AND AFTER A COOL MORNING IN THE MID 40S
TO LOWER 50S...A SLOW MODERATION OF TEMPERATURES TO THE UPPER 60S
AND LOWER 70S IS EXPECTED. THE NEXT APPROACHING FRONT SHOULD
WEAKEN AS IT RUNS INTO WEAKENING SURFACE RIDGE...SO WILL KEEP THE
FORECAST DRY ON SAT AS TEMPERATURES MODIFY TO NORMAL OR A LITTLE
ABOVE.

&&

.AVIATION...
SFC WINDS: THRU 20/15Z...VRBL AOB 3KTS. BTWN 20/15Z-20/18Z...S BTWN
4-7KTS. WNDSHFT TO E/SE 5-8KTS AFT 20/18Z...BTWN 20/18Z-20/20Z CSTL
SITES...BTWN 20/21Z-20/23Z INTERIOR SITES. AFT 21/00Z...VRBL AOB
3KTS.

VSBYS: THRU 20/13Z...LCL MVFR/BRIEF IFR IN BR. AFT 20/13Z VFR ALL
SITES.

CIGS: THRU 20/13Z...AREAS AOA FL120 N OF KTIX-KISM...LCL MVFR CIGS
BTWN FL020-030 CSTL SITES S OF KMLB. AFT 20/13Z...VFR ALL SITES...
PREVAILING CIGS AOA FL120 N OF KMLB-KISM...BCMG FL100-120 AFT 20/18Z.

&&

.MARINE...
TODAY-TONIGHT...A WEAK AND BROAD HI PRES RIDGE BLANKETING THE REGION
FROM THE CAROLINA COAST TO THE BAHAMA BANK WILL GENERATE A LIGHT TO
GENTLE SRLY BREEZE ACRS THE LCL ATLC THRU EARLY AFTN. WINDS WILL
SHIFT TO THE E/SE BY MID AFTN AS THE SEABREEZE FORMS...BUT THE WEAK
PGRAD WILL NOT SUPPORT ANYTHING GREATER THAN 10KTS. WINDS WILL
CONTINUE E/NE OVERNIGHT AS A WEAK FRONTAL BOUNDARY DRIFTS INTO THE
FL PANHANDLE. SEAS AOB 2FT.

SUNDAY...SOUTHEAST FLOW STILL INDICATED AT 10 KNOTS OR LESS. THE
DAY LOOKS QUITE CLOUDY WITH A CHANCE OF SHOWERS LATE IN THE DAY
ESPECIALLY CANAVERAL NORTHWARD.

MON-WED...WINDS WILL BECOME SOUTH/SOUTHWEST AND INCREASE AHEAD OF
A COLD FRONT ESPECIALLY TUE-WED. EXPECT A CHANCE FOR SHOWERS AND
SLIGHT CHANCE FOR STORMS IN A MOIST AIR MASS MON/TUE...BUT A
PERIOD OF STRONG STORMS IS EXPECTED LATE TUE NIGHT AND INTO WED.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  73  59  74  64 /  10  10  30  70
MCO  76  59  77  64 /   0  10  20  50
MLB  77  62  77  66 /   0  10  20  50
VRB  77  61  77  64 /   0  10  10  40
LEE  75  58  76  63 /   0  10  30  70
SFB  76  59  76  64 /   0  10  30  60
ORL  76  60  76  64 /   0  10  30  60
FPR  77  60  77  65 /   0  10  10  30

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
AM...NONE.
&&

$$

SHORT TERM...BRAGAW
LONG TERM....LASCODY





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