Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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000
FXUS62 KTBW 180803
AFDTBW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
403 AM EDT FRI APR 18 2014

...LOCALLY HEAVY RAINFALL POSSIBLE THROUGH TONIGHT...
...SEVERE STORMS POSSIBLE TODAY AND EARLY TONIGHT...
...ROUGH BOATING CONDITIONS EXPECTED OVER THE GULF WATERS...

.SHORT TERM (TODAY - SUNDAY)...
AN AMPLIFYING MID LEVEL TROUGH OVER THE LOWER MS VALLEY EARLY THIS
MORNING WILL GRADUALLY CLOSE OFF OVER THE NORTHERN GULF COAST LATER
TONIGHT THROUGH SATURDAY. THE MID LEVEL TROUGH WILL SUPPORT
CYCLOGENESIS OVER THE EASTERN GULF OF MEXICO TODAY. DEEP MOISTURE
(PW`S 1.7 TO 1.9 INCH RANGE) STREAMING NORTH INTO THE REGION ON AN
INCREASING SOUTHEAST TO SOUTHERLY WIND FLOW AHEAD OF THESE FEATURES
COMBINED WITH DYNAMIC SUPPORT FOR LARGE SCALE LIFT AND AN INCREASINGLY
DIVERGENT FLOW ALOFT WILL SUPPORT HIGH RAIN CHANCES ALONG WITH SOME
LOCALLY HEAVY RAINFALL AMOUNTS ACROSS THE FORECAST AREA TODAY AND
TONIGHT...WITH HIGHEST POPS LIKELY TO RESIDE ACROSS THE NATURE COAST
CLOSEST TO THE ABOVE MENTIONED FEATURES.

IN ADDITION TO THE RAINFALL...AMPLE MOISTURE COMBINED WITH DAYTIME
HEATING WILL PRODUCE CAPE VALUES AOA 1000 J/KG. THIS INSTABILITY
COMBINED WITH BULK SHEAR INCREASING TO AROUND 40 KNOTS VIA BUFKIT
DATA...AND MODEST LOW/MID LEVEL WINDS VEERING WITH HEIGHT AND COLD
MID LEVEL TEMPERATURES (-10 TO -12C AT 500MB) ASSOCIATED WITH THE
MID LEVEL TROUGH WILL INCREASE THE POTENTIAL FOR SOME SEVERE STORMS
ALONG AN INLAND MOVING SEA BREEZE DURING LATE MORNING THROUGH THE
AFTERNOON...WITH THE RISK OF LARGE HAIL AND DAMAGING WINDS AND EVEN
A FEW TORNADOES.

HIGH RAIN CHANCES (POPS 60 PERCENT ) ALONG WITH THE THREAT OF A
SEVERE STORMS WILL CONTINUE ACROSS THE FORECAST AREA THROUGH THE
FIRST HALF OF TONIGHT AS A PRE-FRONTAL BAND OF CONVECTION MOVES IN
FROM THE GULF AHEAD OF A TRAILING COLD FRONT ASSOCIATED WITH A WEAK
SURFACE LOW MOVING NORTHEAST ACROSS THE NORTH FLORIDA. RAIN CHANCES
WILL GRADUALLY DECREASE FROM WEST TO EAST AFTER MIDNIGHT TONIGHT AS
DRIER AIR WRAPPING IN ON THE BACK SIDE OF THE MID LEVEL CLOSED LOW
MOVES INTO THE REGION FROM THE GULF...WITH RAIN CHANCES DECREASING
TO AROUND 30 PERCENT.

THE CLOSED LOW OVER SOUTHERN GA AND ATTENDANT SURFACE LOW IN THE
VICINITY OF KJAX EARLY SATURDAY MORNING WILL MOVE OFF THE SOUTHEAST
U.S. COAST DURING SATURDAY AFTERNOON. WRAP AROUND MOISTURE WITHIN
THE CYCLONIC FLOW WILL LIKELY SUPPORT SLIGHT CHANCES FOR SOME
SHOWERS ACROSS CENTRAL AND NORTHERN ZONES DURING THE DAY...WITH
MAINLY DRY CONDITIONS EXPECTED FAR SOUTH. IT WILL BE BREEZY WITH
WEST TO NORTHWEST WINDS IN THE 15 TO 20 MPH RANGE EXPECTED.

UPPER AND SURFACE RIDGING WILL GRADUALLY BUILD IN FROM THE WEST IN
THE WAKE OF THE DEPARTING CLOSED MID LEVEL LOW AND SURFACE LOW
DURING SATURDAY NIGHT AND SUNDAY WITH PLEASANT DRY WEATHER EXPECTED.
NEAR SEASONAL LEVEL TEMPERATURES TODAY WILL FALL TO BELOW SEASONAL
NORMS DURING SATURDAY AND SATURDAY NIGHT...THEN WILL RETURN TO NEAR
SEASONAL NORMS ON EASTER SUNDAY.

.LONG TERM (SUNDAY NIGHT - THURSDAY)...
THE LONG TERM PERIOD BEGINS WITH THE LOW PRESSURE SYSTEM EXITING
THE REGION ON SUNDAY NIGHT INTO MONDAY. A SECOND FRONTAL SYSTEM
NEARS THE AREA ON TUESDAY...AIDED BY A 500MB TROUGH DIGGING
THROUGH AT THE SAME TIME. THE FRONT WILL BE WEAKENING AS IT MOVES
ACROSS THE STATE TUESDAY NIGHT INTO WEDNESDAY EVENING...LIKELY
WEAK ENOUGH TO LACK MEANINGFUL RAINFALL OPPORTUNITIES. HIGH
PRESSURE BUILDS IN BEHIND THE FRONT TO END THE EXTENDED PERIOD ON
THURSDAY. TEMPERATURES WILL REMAIN SEASONAL...WITH NO MAJOR TASTES
OF CHILLY AIR EXPECTED.

&&

.AVIATION...
VFR EXPECTED THROUGH MUCH OF THE PERIOD...EXCEPT FOR OVERNIGHT AND
MORNING MVFR/IFR DUE TO LOW CIGS. AN APPROACHING FRONTAL SYSTEM WILL
INCREASE SHOWER AND THUNDERSTORM CHANCES LATE IN THE TAF
PERIOD...ALONG WITH PRODUCING GUSTY WINDS. HEAVY RAIN SHOWERS OR
THUNDERSTORMS COULD BRING TERMINALS TO MVFR/BRIEF IFR.

&&

.MARINE...
DEVELOPING LOW PRESSURE OVER THE CENTRAL GULF COMBINED WITH SURFACE
HIGH PRESSURE ALONG THE MID ATLANTIC COAST IS SUPPORTING A 6 MB
GRADIENT OVER THE GULF WATERS THIS MORNING WHICH IS SUPPORTING AN
EASTERLY WIND FLOW AROUND 20 KNOTS OVER THE OFFSHORE WATERS FROM
ENGLEWOOD NORTH TO THE SUWANNEE RIVER WHERE SMALL CRAFT ADVISORY
HEADLINES ARE IN PLACE. ACROSS THE REMAINDER OF THE WATERS WINDS
REMAIN IN THE EXERCISE CAUTION LEVEL AND WILL RETAIN THESE HEADLINES
IN THE 430 AM COASTAL PACKAGE. AS THE SURFACE LOW MOVES EAST NORTHEAST
ACROSS THE NORTHEAST GULF TODAY WINDS WILL VEER TO THE SOUTHEAST AND
SOUTH DURING THE AFTERNOON WITH SIMILAR SPEEDS EXPECTED. TONIGHT A
COLD FRONT WILL MOVE THROUGH THE WATERS AS THE AFOREMENTIONED LOW
MOVES NORTHEAST ACROSS THE NORTHERN PENINSULA. PRE-FRONTAL SOUTHWEST
FLOW WILL SHIFT TO THE WEST AND NORTHWEST AS THE FRONT SWEEPS SOUTH
THROUGH THE WATERS...WITH ELEVATED WINDS/SEAS NEAR ADVISORY LEVELS
EXPECTED TO CONTINUE THROUGH SUNDAY. THESE INCREASING WINDS AND SEAS
WILL BRING ROUGH BOATING CONDITIONS TO THE GULF WATERS AND INLAND
WATERWAYS TODAY ALONG WITH AN INCREASED RISK FOR RIP CURRENTS ALONG
AREA BEACHES. LIGHTER WINDS AND SEAS WILL RETURN TO THE WATERS
EARLY NEXT WEEK AS SURFACE HIGH PRESSURE BUILDS IN OVER THE REGION.

&&

.FIRE WEATHER...
ELEVATED RAIN CHANCES WILL KEEP HUMIDITY VALUES WELL ABOVE CRITICAL
VALUES TODAY. DRIER AIR WILL MOVE INTO THE REGION LATE TONIGHT
THROUGH SUNDAY...HOWEVER RH VALUES SHOULD REMAIN ABOVE CRITICAL
LEVELS WITH NO RED FLAG CONDITIONS EXPECTED. INCREASING 20 FOOT
WINDS AND TRANSPORT WINDS WILL SUPPORT ELEVATED DISPERSION INDICES
ACROSS THE REGION ON SATURDAY AND SUNDAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
TPA  80  66  74  60 /  70  60  20  10
FMY  85  70  81  62 /  40  60  20  10
GIF  83  67  79  58 /  60  60  20  10
SRQ  81  69  75  62 /  60  60  20  10
BKV  82  65  76  54 /  70  60  20  10
SPG  81  67  72  63 /  60  60  20  10

&&

.TBW WATCHES/WARNINGS/ADVISORIES...
FL...FLOOD WATCH FROM 8 AM EDT THIS MORNING THROUGH LATE
     TONIGHT FOR COASTAL LEVY-INLAND LEVY.

GULF WATERS...SMALL CRAFT ADVISORY UNTIL 2 AM EDT SATURDAY FOR ENGLEWOOD
     TO TARPON SPRINGS OUT 20 TO 60 NM-TARPON SPRINGS TO
     SUWANNEE RIVER OUT 20 TO 60 NM.

&&

$$

SHORT TERM/MARINE/FIRE WEATHER...57/MCMICHAEL
LONG TERM/AVIATION...02/GARCIA







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