Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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FXUS62 KTBW 270835
AFDTBW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
335 AM EST FRI FEB 27 2015

.SHORT TERM (TODAY - SATURDAY)...
IT LOOKS LIKE WE WILL SEE A RATHER CLOUDY AND POTENTIALLY WET END
TO THE WEEK. MODELS ARE IN GOOD AGREEMENT REGARDING THE SYNOPTIC
SET UP...WHICH INCLUDES A BROAD UPPER-LEVEL TROUGH PRODUCING
GENERALLY ZONAL...BUT SLIGHTLY CYCLONIC FLOW OVERHEAD. AT THE
SURFACE...A LARGE HIGH CENTER WITH A PRESSURE NEAR 1045MB WILL BE
SITUATED TO OUR NORTH...AND A WEAKENING FRONTAL BOUNDARY IN THE
FLORIDA STRAITS TO OUR SOUTH.

STARTING DOWN NEAR THE TIGHT PRESSURE GRADIENT BETWEEN THE TWO
SURFACE FEATURES MENTIONED ABOVE WILL PUT OUR ENTIRE REGION UNDER A
MODERATELY STRONG EASTERLY WIND FLOW. AS IS TYPICAL WITH THIS SETUP
THIS TIME OF YEAR...AN INVERTED TROUGH WILL TRY TO BECOME
ESTABLISHED IN THE EASTERLY FLOW OVER THE GULF STREAM BETWEEN
FLORIDA AND THE BAHAMAS. THE STRONG EAST FLOW WILL DISPLACE THE
TROUGH WESTWARD OVER THE PENINSULA DURING SATURDAY. LOW-LEVEL WIND
SPEED CONVERGENCE BECOMES MAXIMIZED NEAR THE TROUGH AXIS WHERE WINDS
BECOME A BIT LIGHTER. THIS FEATURE ON ITS OWN WOULD BE CAPABLE OF
PRODUCING SHALLOW CONVECTION WITH LIGHT MODERATE SHOWERS.

NOW MOVING OUR WAY HIGHER INTO THE ATMOSPHERE...THE BROAD
UPPER-LEVEL TROUGH WILL PROVIDE A LONG FETCH OF INCREASINGLY MOIST
SOUTHWESTERLY FLOW WHICH WILL OVER-RUN THE SHALLOW COOL AIRMASS AT
THE SURFACE. WEAK UPGLIDE TODAY SHOULD BE SHALLOW AND CONFINED TO
THE SOUTHERN HALF OF OUR AREA CLOSER TO THE FRONTAL BOUNDARY. BEST
RAIN CHANCES WOULD BE SOUTH OF THE I-4 CORRIDOR...BUT EVEN THERE
AMOUNTS SHOULD BE QUITE LIGHT AND RAIN WILL BE OF THE OFF AND ON
NATURE.

ON SATURDAY...UPGLIDE INCREASES IN DEPTH AND BEGINS TO SHIFT NORTH.
RAINFALL COULD BE STEADIER AND HEAVIER ON SATURDAY...ALTHOUGH
DIFFERENCES IN THE AMOUNT AND LOCATION OF LIFT EXIST BETWEEN MODELS.
THE MORE SHALLOW SHOWERY TYPE OF RAIN WILL MORE PREVALENT OVER OUR
SOUTHERN INLAND LOCATIONS. A STEADIER AND POTENTIALLY HEAVIER RAIN
WITH EMBEDDED DEEPER SHOWERS SHOULD SET UP SOMEWHERE ALONG OR NORTH
OF THE I-4 CORRIDOR.

DUE TO UNCERTAINTIES IN THE FORECAST...WE HAVE GENERALLY
BROAD-BRUSHED 30 TO 40 PERCENT RAIN CHANCES FOR MOST OF THE DAY ON
SATURDAY. WE MAY BE ABLE TO REFINE THIS A BIT BETTER LATER TODAY...
OR CERTAINLY BY EARLY SATURDAY AS THESE SYNOPTIC AND MESOSCALE
FEATURES PLAY OUT.

.LONG TERM (SUNDAY THROUGH NEXT THURSDAY)...
LONG TERM FORECAST PERIOD BEGINS ON SUNDAY WITH A GENERALLY ZONAL
FLOW PATTERN IN PLACE ALOFT ACROSS THE NORTHERN GULF COAST...ALIGNED
ABOVE A BUILDING RIDGE WHICH LOOKS TO BRING SOME VERY WARM
CONDITIONS TO THE FORECAST AREA FOR THE EARLY AND MIDDLE PORTION OF
NEXT WEEK. AT LEAST FOR SUNDAY WE WILL STILL BE DEALING WITH AN
MODERATE EASTERLY FLOW AROUND THE SOUTHERN PERIPHERY OF A 1035+
RIDGE ALONG THE EASTERN SEABOARD. ALTHOUGH NOT AS PRONOUNCED AS IS
EXPECTED ON SATURDAY...THE MODEL CONSENSUS IS STILL FOR A BROAD LOW
LEVEL UPGLIDE REGIME TO BE IN PLACE ABOVE THE BOUNDARY LAYER ON
SUNDAY. THIS LIFT WILL AID THE DEVELOPMENT OF SPEED CONVERGENCE
SHOWERS PUSHING RAPIDLY INLAND WITH THE LOW LEVEL FLOW FROM THE FL
EAST COAST. AGAIN...THE SETUP IS NOT AS GOOD FOR THE SHOWERS AS
SATURDAY...BUT STILL NEED TO MENTION AT LEAST A SLIGHT CHANCE OF
SHOWERS/SPRINKLES OVER THE MAJORITY OF THE AREA...ALONG WITH MORE
CLOUDS THAN SUN. BETTER CHANCES FOR NUMEROUS SUNNY BREAKS TO OCCUR
SHOULD BE DURING THE LATER PORTION OF THE DAY...AND THE FURTHER
SOUTH ONE TRAVELS. TEMPERATURES WILL BE STARTING TO CLIMB BY
SUNDAY...BUT JUST HOW MUCH WILL DEPEND ON THE AMOUNT AND DURATION OF
LOWER CLOUDS WITHIN THE UPGLIDE REGIME. MOS CONSENSUS IS FOR 70S
NORTH OF I-4 AND LOWER 80S FURTHER SOUTH. THESE NUMBERS MAY NEED TO
BE NUDGED DOWN WITH FUTURE FORECASTS...BUT FEEL CONFIDENT THAT THEY
ARE AT LEAST IN THE BALLPARK.

THE EARLY AND MIDDLE PORTION OF NEXT WEEK WILL FEATURE MID/UPPER
LEVEL RIDGING AMPLIFYING NORTHWARD OUT OF THE WESTERN CARIBBEAN TO
CONTROL THE EASTERN GULF OF MEXICO AND FL PENINSULA. THE SURFACE
RIDGE MOVING INTO THE WESTERN ATLANTIC WILL ALLOW A WEAKER GRADIENT
BUY THIS TIME...AND A SHIFT IN WINDS TO THE SOUTHEAST AND SOUTH WITH
TIME. THE END RESULT LOOKS TO BE A GENERALLY DRY PERIOD THROUGH
WEDNESDAY WITH ABOVE NORMAL TEMPERATURES. ANY DAY WITH A WEAK
ENOUGH GRADIENT TO ALLOW FOR A DEFINED SEA-BREEZE MAY SEE A FEW
ISOLATED AFTERNOON SHOWERS...HOWEVER THIS IS A BIT FAR INTO THE
EXTENDED TO TRY AND PIN-POINT THE MOST FAVORABLE LOCATIONS...AND ANY
SHOWERS THAT FORM ALONG THE SEA-BREEZE WOULD BE SHORT-LIVED AND
CERTAINLY NOT ANYTHING TO DETER OUTDOOR PLANS.

THE GLOBAL GUIDANCE BEGINS TO DIVERGE RAPIDLY AS WE HEAD INTO THE
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT PERIOD. THE DIFFERENCES ARE
RELATED TO THE INTERACTION BETWEEN NORTHERN STREAM ENERGY DROPPING
INTO THE MID-SECTION OF THE COUNTY AND ADDITIONAL ENERGY EJECTING
EASTWARD ACROSS NORTHERN MEXICO/DEEP SOUTH. THE GFS IS THE MOST
AGGRESSIVE WITH PHASING THIS ENERGY AND DEEPENING THE LONGWAVE
TROUGH...AND ALSO FASTEST TO PUSH A COLD FRONT THROUGH THE REGION ON
THURSDAY. THE ECMWF DOES A LESS EFFECTIVE JOB AT PHASING THIS ENERGY
AND KEEPS THE TROUGH LESS AMPLIFIED AND OVERALL SLOWER. THE RESULT
OF THIS ACTION IS TO DELAY THE FRONTAL PASSAGE UNTIL THURSDAY
NIGHT/EARLY FRIDAY...AND ALSO FOR THE PASSAGE TO BE LESS
SUBSTANTIAL. LOOKING AT THE INDIVIDUAL GFS ENSEMBLE MEMBERS...THE
MAJORITY TEND TO LEAN TOWARD A LESS AMPLIFIED PATTERN AND/OR SLOW
PROGRESSION EASTWARD COMPARED TO THE OPERATIONAL RUN. WITH THIS IN
MIND HAVE LEANED TOWARD THE SLOWER ECMWF SOLUTION.

&&

.AVIATION...
LONG DURATION OF MAINLY MVFR CEILINGS EXPECTED NEXT 24 HOURS. SOME
LIFTING WITH BREAKS COULD OCCUR BETWEEN 18Z AND 00Z TODAY.

&&

.MARINE...
LARGE HIGH PRESSURE TO THE NORTH AND WEAKENING FRONTAL BOUNDARY TO
OUR SOUTH WILL KEEP OUR REGION UNDER ENHANCED EASTERLY FLOW THROUGH
THE WEEKEND. ONCE THE HIGH MOVES OFF THE ATLANTIC COAST SUNDAY
NIGHT...IT WILL BEGIN TO SINK SOUTH AND RIDGE BACK ACROSS FLORIDA
AND THE NORTHERN GULF RESULTING IN LIGHTER WINDS AND MORE FAVORABLE
SEAS.

WINDS IN THE MIDDLE OF TAMPA BAY HAVE BEEN RUNNING AROUND 15 KNOTS
WITH SOMEWHAT LESSER VALUES CLOSER TO THE COASTLINE. WINDS OFFSHORE
HAVE BEEN MAINLY AROUND 15 KNOTS...BUT ARE EXPECTED TO INCREASE A
BIT TODAY...AND ESPECIALLY TONIGHT WITH AN EASTERLY SURGE. WILL
HEADLINE EXERCISE CAUTION FOR TODAY IN ALL WATERS EXCEPT TAMPA BAY
AND CHARLOTTE HARBOR. WE MAY EVEN NEED A SHORT DURATION SMALL CRAFT
ADVISORY FOR PORTIONS OF THE WATERS TONIGHT.

&&

.FIRE WEATHER...
NO FIRE WEATHER CONCERNS NEXT SEVERAL DAYS.

&&

.PRELIMINARY POINT TEMPS/POPS...
TPA  65  55  75  63 /  10  10  30  30
FMY  71  61  80  66 /  30  10  30  20
GIF  65  56  74  63 /  20  20  40  40
SRQ  67  57  77  64 /  20  10  30  20
BKV  65  53  72  60 /   0  20  30  40
SPG  65  58  73  64 /  10  10  30  20

&&

.TBW WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GULF WATERS...NONE.

&&

$$

SHORT TERM/AVIATION/MARINE/FIRE WEATHER...JILLSON
LONG TERM/DECISION SUPPORT...MROCZKA




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