Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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000
FXUS62 KTBW 010815
AFDTBW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
315 AM EST SUN MAR 01 2015

.SYNOPSIS...
08Z WATER VAPOR AND H4 RAP ANALYSIS SHOWS CONVERGENT UPPER LEVEL
FLOW ACROSS THE MID-SECTION OF THE COUNTY AS ONE BRANCH OF THE
NORTHER STREAM DIPS INTO THE UPPER MIDWEST/NORTHERN PLAINS...AND A
SECOND BRANCH DROPS DOWN THE PACIFIC COAST AROUND A LARGE CUTOFF LOW
OVER CALIFORNIA...AND EJECTS OUT OF THE SOUTHWESTERN STATES INTO THE
CENTRAL PLAINS. HIGH LEVEL SOUTHERN STREAM MOISTURE CAN BE SEEN VERY
WELL ON WV IMAGERY MOVING ACROSS CENTRAL MEXICO...THE GULF OF MEXICO
AND OVER THE FL PENINSULA. SOUTH OF THIS SOUTHERN STREAM WE FIND A
LARGE WEST-EAST ORIENTED UPPER RIDGE IN PLACE FROM THE BAY OF
CAMPECHE ACROSS TO THE WESTERN CARIBBEAN. OVER THE NEXT 36-48
HOURS...AS THE WESTERN TROUGH/CUTOFF LOW DIGS FURTHER SOUTH...AND
HEIGHTS FALL ACROSS THE SOUTHWESTERN STATES...THIS WILL FORCE THE
DOWNSTREAM RIDGE TO AMPLIFY NORTHWARD OVER THE GULF OF MEXICO AND
FLORIDA PENINSULA. ALL THIS TRANSLATES INTO A WARM AND SPRING-LIKE
FORECAST FOR OUR REGION DURING THE EARLY AND MIDDLE PORTION OF THE
WEEK.

AT THE SURFACE...STRONG HIGH PRESSURE CONTINUES TO RIDGE DOWN THE
ATLANTIC SEABOARD INTO THE SOUTHEAST CONUS AND WAS THE SET UP FOR
THE OVERRUNNING/UPGLIDE PATTERN THAT BROUGHT ALL THE RAIN TO PARTS
OF THE REGION ON SATURDAY. THE INFLUENCE OF THIS RIDGE IS JUST NOW
BEGINNING TO SLACKEN AS IT WEAKENS AND MOVES OFF INTO THE WESTERN
ATLANTIC. THIS ACTION WILL CONTINUE TO WEAKEN THE THE DEPTH OF
UPGLIDE REGIME AND SLOWLY SHUT DOWN THE SHOWER PRODUCTION THROUGH
THE REMAINDER OF THE EARLY MORNING HOURS. LINGERING UPGLIDE IN THE
LOWEST LEVELS ALONG THE 295-300K SURFACES WILL KEEP THE POTENTIAL
FOR LOWER STRATUS...AND RESULT IN A DIFFICULT AVIATION FORECAST
THROUGH THE MORNING HOURS. HOWEVER...AT LEAST THINGS WILL START TO
DRY OUT...TEMPORARILY.

&&

.SHORT TERM (TODAY THROUGH MONDAY)...
TODAY...
SUNDAY WILL BE A TRANSITION DAY IN THE WEATHER PATTERN FROM ONE
DOMINATED BY THE SURFACE HIGH RIDGING DOWN THE ATLANTIC SEABOARD
INTO OUR REGION...TO ONE COMING UNDER THE INFLUENCE MORE AND MORE
FROM A BUILDING UPPER LEVEL RIDGE OUT OF THE CARIBBEAN. AS MENTIONED
IN THE SYNOPSIS...THE DEEP LAYER UPGLIDE IS SHOWN BY MOST NUMERICAL
GUIDANCE TO HAVE SHIFTED OFF TO THE NORTHEAST BY SUNRISE...HOWEVER A
LOWER LEVEL LAYER OF UPGLIDE WILL STILL BE IN PLACE AND BE HELPING
TO SUPPORT AREAS OF LOWER STRATUS INTO THE MORNING HOURS. THIS WILL
ESPECIALLY BE TRUE ACROSS THE CENTRAL AND NORTHERN PORTIONS OF THE
PENINSULA. FURTHER SOUTH...ON THE OTHER SIDE OF A WEAK BOUNDARY
ACROSS THE STATE...EARLY MORNING SATELLITE IMAGERY IS ALREADY
SHOWING IMPROVING CONDITIONS (IN TERMS OF CLOUD COVER)...AND THIS
SHOULD EXPAND UP INTO OUR SOUTHERN ZONES DURING THE MORNING.

OVER TIME WILL SEE MORE AND MORE SUNNY BREAKS FURTHER NORTH AS
WELL...AND WILL HAVE EVERYONE GOING PARTLY CLOUDY FOR THE AFTERNOON
HOURS. WITH THE SUNNY BREAKS...WE WILL BE SEEING STRONG TERRESTRIAL
HEATING...WITH TEMPS CLIMBING WELL UP INTO THE 70S TO THE NORTH OF
THE I-4 CORRIDOR...AND INTO THE UPPER 70S/LOWER 80S FURTHER SOUTH.
THE LOCAL GRADIENT WILL BE RELAXING OVER TIME AS WELL AS THE SURFACE
RIDGE WEAKENS AND EXITS INTO THE WESTERN ATLANTIC. THIS WEAKENING OF
THE GRADIENT WILL ALLOW A DECENT SEA-BREEZE CIRCULATION TO DEVELOP
AFTER 18Z...AND IN FACT ALL THE HIRES GUIDANCE SHOW THIS TURNING OF
THE WINDS ONSHORE NEAR THE COAST.

WHILE WE EXPECT THE MORNING TO BE MOSTLY DRY ACROSS THE REGION...WE
CAN NOT KEEP THE FORECAST RAIN FREE COMPLETELY FOR THE AFTERNOON AND
EVENING HOURS. A COUPLE OF THINGS COME INTO PLAY HERE. THE FIRST IS
THE STRONG HEATING OVER LAND WILL ALLOW FOR AT LEAST A FEW HUNDRED
J/KG OF BL CAPE THIS AFTERNOON. THE DIFFERENTIAL HEATING ALONG WITH
HELPING TO FORCE THE SEA-BREEZE...IS ALSO SHOWING BY THE GUIDANCE
SUITE TO STRENGTHEN AN INVERTED SURFACE TROUGH ACROSS THE
CENTRAL/WESTERN PORTIONS OF THE PENINSULA FOR THE SECOND HALF OF THE
DAY. THIS TROUGH IS PARTICULARLY PRONOUNCED IN THE NAM/SREF AND
HIRES MEMBERS. THE TROUGH WILL HELP TO FOCUS LOW LEVEL CONVERGENCE
BY MID/LATE AFTERNOON GENERALLY ALONG THE I-75 CORRIDOR. WHEN ONE
ADDS THE EVENTUAL ADDITIONAL FOCUS/CONVERGENCE FROM THE
SEA-BREEZE...IT BECOMES CLEAR THAT UPDRAFTS SUPPORTING LIMITED
CONVECTION CAN NOT BE RULED OUT. IN FACT...THE LAST 4 RUNS OF THE
LOCAL WRFARW...ALONG WITH THE LATEST NCEP HIRES RUNS ARE REMARKABLY
SIMILAR IN THE PATTERN OF ALLOWED CONVECTION DEVELOPING AFTER 19-20Z
ALONG THIS I-75 CORRIDOR. WITH ALL THIS IN MIND HAVE GONE WITH A 30%
POP FOR SCT SHOWERS/ISOLATED THUNDERSTORMS FOR THE LATER AFTERNOON
THROUGH MIDDLE EVENING HOURS. IF THE HIRES RUNS ARE CORRECT...THEN
THE GREATEST THREAT FOR AN AFTERNOON SHOWER WOULD EXIST WITHIN ABOUT
30 MILES EITHER SIDE OF I-75...HOWEVER...HAVE GONE A BIT MORE BROAD
THAN THAT WITH THE FORECAST FOR NOW...AND WILL ALLOW THE DAY SHIFT
TO EVALUATE THE PATTERN EVOLUTION...AND ADD A BIT MORE TEMPORAL
AND/OR SPATIAL DETAIL. THE CONVECTION IS NOT GOING TO BE VERY
ROBUST...AND CERTAINLY NOT EXPECTING ANY STRONG STORMS AT THIS
TIME...HOWEVER A BRIEF DOWNPOUR...AND A FEW LIGHTNING STRIKES SHOULD
BE PLANNED FOR IF OUTDOORS LATER TODAY.

TONIGHT...
WIDELY SCATTERED CONVECTIVE CELLS WILL LINGER INTO THE MIDDLE
EVENING HOURS...MAINLY TO THE NORTH OF THE I-4 CORRIDOR...AND THEN
BEGIN TO DISSIPATE WITH THE LOSS OF DIURNAL HEATING AND RESULTING
LOSS OF SURFACE FOCUS. WILL END ALL SHOWERS BY 03-04Z...WITH A DRY
OVERNIGHT PERIOD THEREAFTER. FOCUS INTO THE LATER OVERNIGHT HOURS
WILL SHIFT TO THE POTENTIAL FOR AREAS OF DENSE FOG DEVELOPMENT. A
MOIST BOUNDARY LAYER WILL STILL BE IN PLACE...AND AS WE START TO SEE
THE UPPER RIDGE BUILD...AND INCREASED LARGE SCALE SUBSIDENCE...THE
SETUP FOR FOG IS FAIRLY GOOD. IN FACT...THE LATEST SREF
PROBABILITIES OF VISIBILITY LESS THAN 1 MILE DURING THE LATE NIGHT
HOURS TONIGHT IS GREATER THAN 80% ACROSS MUCH OF THE REGION. IT HAS
BEEN MY EXPERIENCE TO BEGIN TAKING THE SREF FOG POTENTIAL SERIOUSLY
WHEN PROBABILITIES BEGIN TO EXCEED 70% OR SO. HAVE ADDED AREAS OF
FOG INTO THE GRIDS...AND AGAIN WILL LET THE DAY SHIFT REEVALUATE
BEFORE ADDING DENSE FOG WORDING TO THE FORECAST. FOR NOW...JUST BE
AWARE THAT SOME LOCATIONS MAY HAVE A MORE DIFFICULT MONDAY MORNING
COMMUTE RESULTING FROM VISIBILITY REDUCTIONS. LOW TEMPERATURES EARLY
MONDAY MORNING WILL RANGE FROM THE UPPER 50S OVER LEVY COUNTY...TO
THE LOWER/MIDDLE 60S ELSEWHERE.

MONDAY...
UPPER RIDGE WILL TAKE FIRM CONTROL OVER OUR WEATHER DURING THE DAY.
WILL BE EXPECTING A FAIR AMOUNT OF SUN...AFTER ANY MORNING FOG BURNS
OFF (WHICH MAY TAKE SEVERAL HOURS). FORECASTING ABOVE AVERAGE
TEMPERATURES ACROSS THE REGION AS BOUNDARY LAYER SHOULD BE ABLE TO
EASILY MIX OUT TO THE UPPER 70S ACROSS THE FAR NORTH (LEVY/CITRUS
COUNTIES)...AND LOWER TO MIDDLE 80S FOR MOST OTHER AREAS. THE STRONG
HEATING FORCES ANOTHER SEA-BREEZE TO DEVELOP...AND THIS WILL LIKELY
KEEP TEMPERATURES DOWN A BIT (MID/UPPER 70S) ALONG THE IMMEDIATE
COAST...AS THE FLOW DEVELOPS OFF THE COOLER SHELF WATERS.
HOWEVER...IT WILL NOT TAKE MUCH DISTANCE INLAND TO FIND THE LOWER
80S AGAIN.

THE POTENTIAL FOR A BRIEF AFTERNOON SHOWER ALONG THE SEA-BREEZE IS
NOT ZERO...HOWEVER WITH THE RIDGE BUILDING OVERHEAD...CONDITIONS ARE
NOT AS FAVORABLE AS WE MIGHT SEE THIS AFTERNOON...AND GIVEN THE TIME
OF YEAR...IF THINGS DO NOT LINE UP JUST RIGHT...THEN CONVECTION IS
REALLY NOT THAT LIKELY. FOR NOW WILL KEEP THE FORECAST GENERALLY DRY
MONDAY AFTERNOON. CAN TAKE ANOTHER LOOK AT THIS TONIGHT.

&&

.LONG TERM (TUESDAY THROUGH NEXT SATURDAY)...
THROUGH WED; THE AREA WILL BE DOMINATED BY DEEP LAYER RIDGING THAT
GRADUALLY SLIDES EAST. INITIALLY  THE PATTERN ALOFT BEGINS WITH A
LONG WAVE TROUGH FROM CENTRAL CANADA TO THE GREAT BASIN...RIDGING
CENTERED OVER THE YUCATAN THAT REACHED ACROSS THE UPPER GREAT
LAKES...AND ANOTHER TROUGH FROM QUEBEC SOUTH OVER NEW ENGLAND AND
THE CANADIAN MARITIMES TO ATLANTIC WATERS. SURFACE HIGH PRESSURE
CENTERED IN THE OHIO VALLEY...AND SPRAWLING DOWN ACROSS THE GULF
REGION SHIFTS OUT OVER THE OPEN ATLANTIC WHILE RIDGING BACK ACROSS
FL TO THE GULF. THE UPPER RIDGE KEEPS THE ATMOSPHERE STABLE WARM AND
GENERALLY DRY. THE TRACK OF THE SURFACE HIGH WILL VEER WINDS FROM
NORTHEAST AND EAST TO SOUTHEAST AND SOUTHERLY. THE SOUTHERLY WINDS
WILL BRING IN SOME WARM AND MORE HUMID AIR WHICH COULD RESULT IN
SEA FOG AS IT MOVES ACROSS THE COOLER GULF WATERS.

THU-FRI; THE WESTERN LONG WAVE TROUGH...WITH AN ACCOMPANYING COLD
FRONT...BY NOW STRETCHES FROM THE FOUR CORNERS REGION TO THE UPPER
GREAT LAKES. THE TROUGH THEN BEGINS TO SHEAR OUT WITH THE EASTERN
PORTION DE-AMPLIFYING AS IT SHIFTS OFF THE NORTHEAST U.S. COAST
WHILE THE WESTERN END MEANDERS NEAR NORTHERN BAJA CALIFORNIA. THE
GULF UPPER RIDGE FLATTENS AND HANGS ON FROM THE YUCATAN ACROSS CUBA
TO THE ATLANTIC EAST OF THE BAHAMAS. AS A RESULT NEARLY ZONAL FLOW
SETS UP ACROSS THE SOUTHEAST CONUS AND GULF REGION...WITH THE FRONT
GETTING STRUNG OUT FROM WEST TO EAST ON OR NEAR THE GULF COAST. HIGH
PRESSURE BUILDS IN NORTH OF THE FRONT AND TRACKS EAST...WITH NORTH
THEN NORTHEAST WINDS EVENTUALLY BRIDGING THE FRONT AND FILLING IN
ACROSS THE AREA. INCREASING MOISTURE ALONG WITH THE FRONT
APPROACHING FROM THE NORTH WILL SUPPORT SOME SLIGHT CHANCE SHOWERS
AND THUNDERSTORM...INITIALLY ACROSS THE NORTH BUT THAT SPREAD
SOUTHWARD WITH TIME. TEMPERATURES THU RUN ABOVE NORMAL BUT COOL ON
FRI...TO NEAR NORMAL CENTRAL AND SOUTH BUT NEAR TO A BIT BELOW
NORMAL IN THE NORTH WHERE THERE WILL BE MORE RAINFALL AND CLOUDS.

SAT; THE BAJA TROUGH BEGINS WORKING EAST...ALONG THE SOUTHWEST CONUS
OR NORTHWEST MEXICO BORDER REGIONS...WITH FLOW ALOFT STARTING TO
BACK TO WEST-SOUTHWEST. THE FRONT RESIDES ALONG THE GULF COAST IN
THE ECMWF SOLUTION WITH SOMEWHAT DRIER CONDITIONS IN FL OR OVER THE
NORTHERN GULF WATERS AND NORTH FL WITH THE GFS SOLUTION...KEEPING
SLIGHTLY MORE RAINFALL OVER OR NEAR THE AREA. IN EITHER CASE THERE
WILL BE SLIGHT CHANCE TO LOW END CHANCE SHOWERS OR STORMS.
TEMPERATURES CONTINUE NEAR NORMAL CENTRAL AND SOUTH AND JUST UNDER
IN THE NORTH.

&&

.AVIATION...
SO FAR...THE CONDITIONS HAVE NOT BE AS PESSIMISTIC AS THE
STATISTICAL GUIDANCE PREDICTED AT MOST TERMINALS. WILL CONTINUE THIS
TREND FOR THE REMAINDER OF THE OVERNIGHT. ALTHOUGH A FEW PERIODS OF
IFR CIGS ARE CERTAINLY POSSIBLE...THE MAJORITY OF THE TIME SHOULD BE
MVFR AND WILL CHOOSE TO STAY IN THE RANGE OVER THE NEXT SEVERAL
HOURS. PERIODS OF MVFR CIGS SHOULD SLOWLY IMPROVE AFTER SUNRISE AND
BRING ALL TERMINALS BACK TO VFR FOR THE MIDDAY/AFTERNOON/EVENING
HOURS. THERE IS THE POTENTIAL FOR WIDELY SCT SHOWERS AND ISOLATED
STORMS AFTER 19-20Z...LINGERING THROUGH 00-02Z. ANY SHOWERS WILL BE
BRIEF AND HAVE USED VCSH TO HIGHLIGHT THIS POTENTIAL. ANY SHOWERS
DISSIPATED BY LATE EVENING AND FOCUS SHIFTS TO FOG POTENTIAL AFTER
MIDNIGHT. BOTH STATISTICAL AND ENSEMBLE GUIDANCE ARE BEGINNING TO
SUGGEST THE POTENTIAL FOR AREAS OF IFR FOG AFTER 06Z.

&&

.MARINE...
HIGH PRESSURE TO OUR NORTH WILL WEAKEN TODAY ALLOWING THE GRADIENT
TO RELAX AND WIND FIELDS TO WEAKEN. THE GRADIENT WILL RELAX ENOUGH
BY THIS AFTERNOON TO ALLOW SEA BREEZE FORMATION WITH WINDS BECOMING
LIGHT ONSHORE THROUGH THE EARLY EVENING. THE GENERALLY SYNOPTIC
EASTERLY FLOW WILL SHIFT SOUTHEAST ON TUESDAY AND THEN SOUTH BY
WEDNESDAY. EXPECT NEARSHORE WINDS TO BECOME ONSHORE EACH AFTERNOON
AND EARLY EVENING. THERE IS THE POTENTIAL WITH THE MOIST SOUTHERLY
FLOW FOR AREAS OF SEA FOG TO REDUCE VISIBILITY BY LATER TUESDAY OR
WEDNESDAY...AND THIS POTENTIAL WILL NEED TO BE MONITORED CLOSELY. A
COLD FRONT IS SCHEDULED TO ARRIVE LATER THURSDAY OR THURSDAY NIGHT
WHICH WOULD END THE THREAT FOR SEA FOG FOR THE END OF THE WEEK...AND
SHIFT WINDS BACK FROM THE NORTH AND NORTHEAST.

&&

.FIRE WEATHER...
NO SIGNIFICANT FIRE WEATHER CONCERNS OUTSIDE OF FOG POTENTIAL ARE
ANTICIPATED OVER THE NEXT SEVERAL DAYS AS RELATIVE HUMIDITY REMAINS
WELL ABOVE CRITICAL LEVELS AND ERC VALUES ARE LOW ACROSS THE REGION.
TEMPERATURES WILL HOWEVER BE ABOVE AVERAGE FOR MUCH OF THE EARLY AND
MIDDLE PORTION OF THE WEEK.

FOG POTENTIAL...
AREAS OF FOG ARE EXPECTED TO DEVELOP TONIGHT INTO EARLY MONDAY
MORNING ACROSS MUCH OF WEST-CENTRAL AND SOUTHWEST FLORIDA. THE FOG
HAS THE POTENTIAL TO BECOME LOCALLY DENSE AT TIME. AREAS OF FOG ARE
ALSO FORECAST FOR LATER MONDAY NIGHT INTO TUESDAY MORNING.

&&

.PRELIMINARY POINT TEMPS/POPS...
TPA  78  65  79  64 /  30  10  10   0
FMY  82  65  83  64 /  30  10  10   0
GIF  80  65  81  63 /  30  20  10  10
SRQ  78  63  79  62 /  20  10  10   0
BKV  80  60  80  59 /  30  20  10   0
SPG  78  65  78  65 /  20  10  10   0

&&

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

&&

$$

SYNOPSIS/SHORT TERM/MARINE/AVIATION/FIRE WX...MROCZKA
LONG TERM/DECISION SUPPORT SERVICES...RUDE




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