Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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000
FXUS62 KTBW 011728
AFDTBW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
128 PM EDT SUN MAY 1 2016

AVIATION...
01/18Z CYCLE. PREVAILING VFR WITH SCT-BKN CUMULUS FIELD NOW IN
PLACE. LIGHT SE TO EAST WINDS BEGINNING TO SHIFT ONSHORE ALONG
THE COAST...AND WILL SEE THIS SHIFT REACH KPIE/KTPA IN NEXT COUPLE
OF HOURS. ISOLATED SHOWERS/STORMS ALONG THE SEA- BREEZE LATE
AFTERNOON/EARLY EVENING. BEST POTENTIAL FOR A BRIEF SHOWER BETWEEN
20-00Z FOR KPGD/KFMY/KRSW...AND ADDED VCTS TO THESE TERMINALS.
SOME POTENTIAL FOR ISOLATED STORMS TO MIGRATE CLOSER TO TAMPA BAY
TERMINALS AFTER 00Z...BUT CONFIDENCE NOT GREAT ENOUGH TO INCLUDE
IN CURRENT TAF ISSUANCE.

&&

.PREV DISCUSSION... /ISSUED 1150 AM EDT SUN MAY 1 2016/

SYNOPSIS...
15Z WATER VAPOR AND H4 RAP ANALYSIS SHOWS A MID/UPPER LAYER
WESTERLY FLOW PATTERN IN PLACE ACROSS THE GULF OF MEXICO AND
FLORIDA PENINSULA. SOUTHERN STREAM JET CROSSES OVER NORTHERN
MEXICO AND ACROSS THE GULF...WITH THE NOSE OF THE MAIN JETSTREAK
OVER OUR REGION. NORTHERN STREAM JET IS IN FAIRLY CLOSE PROXIMITY
TO THE NORTH...CROSSING OVER THE SOUTHERN/CENTRAL PLAINS...TO THE
MID MS AND OHIO VALLEYS. 01/12Z KTBW SOUNDING PROFILE SAMPLED
THESE WINDS ALOFT WELL...SHOWING A DEEP LAYER WEST FLOW ABOVE
700MB.

AT THE SURFACE...ATLANTIC HIGH PRESSURE CONTINUES TO RIDGE BACK TO
THE WEST OVER THE FLORIDA PENINSULA AND EASTERN GULF OF MEXICO. A
COMPLEX FRONTAL SYSTEM REMAINS WELL TO OUR NORTH AND NORTHWEST
FROM SOUTHERN TEXAS TO THE LOWER MS VALLEY AND NORTHEAST INTO THE
OHIO VALLEY. CLUSTERS OF SHOWERS AND STORMS ARE FORMING AND
ONGOING IN ADVANCE OF THIS FRONT...BUT WILL ALSO REMAIN WELL
REMOVED FROM OUR FORECAST AREA. THE ONLY IMPACT FROM THESE STORMS
THAT WE MAY SEE IS AN INCREASE IN HIGH CLOUDS LATER TODAY ACROSS
THE NORTHERN NATURE COAST ZONES ASSOCIATED WITH ANVIL BLOWOFF
ADVECTING DOWNSTREAM IN THE SYNOPTIC UPPER FLOW.

SHORT TERM (REST OF TODAY THROUGH MONDAY)...
BENIGN WEATHER WILL CONTINUE FOR THE NEXT SEVERAL HOURS AS
TEMPERATURES CONTINUE TO CLIMB THROUGH THE 80S...TOWARD AFTERNOON
HIGH TEMPS IN THE VICINITY OF 90 AWAY FROM THE BEACHES. THE STRONG
TERRESTRIAL HEATING WILL EVENTUALLY VEER WINDS NEAR THE COAST
ONSHORE...MAINLY AFTER 18Z. WITH THE SYNOPTIC FLOW FROM THE
SOUTHEAST...THE FLORIDA EAST COAST SEA-BREEZE WILL RACE ACROSS THE
STATE AND SET UP THE MAIN CONVERGENCE ZONE WITH THE WEST COAST
SEA-BREEZE SOMEWHERE NEAR OR JUST EAST OF THE I-75 CORRIDOR DURING
THE LATE AFTERNOON/EARLY EVENING HOURS.

LIKELY THE MOST IMPORTANT FEATURE FOR OUR FORECAST SAMPLED IN THE
KTBW SOUNDING COLUMN THIS MORNING...IS THE DEFINED
SUBSIDENCE/CAPPING INVERSION SEEN BETWEEN 700-625MB. THIS IS A
SIGNIFICANT OBSTACLE FOR PARCELS TO OVERCOME TODAY IN THE PROCESS
OF CONVECTION. ALLOWING FOR DAYTIME MIXING TO OCCUR UP TO A
SURFACE TEMP AROUND 90 STILL HAS TROUBLE OVERCOMING THIS CAP.
CERTAINLY SEEMS LIKE MANY OF THE 06Z GUIDANCE MEMBERS
UNDERESTIMATED THE STRENGTH OF THIS CAP...AND HAVE NOTICED THE
LATEST HRRR BUFR SOUNDINGS ARE HAVING A MORE DIFFICULT TIME
BREAKING THE CAP INTO FREE CONVECTION COMPARED TO EARLIER RUNS
THAT WERE NOT UTILIZING THIS REAL-TIME SOUNDING DATA.

THIS CAP WILL CERTAINLY DELAY THE ONSET OF ANY CONVECTION AS WE
WILL NEED TO REACH ABSOLUTE PEAK HEATING IF PARCELS ARE GOING TO
HAVE ANY CHANCE OF GETTING BY THIS INVERSION. LIKELY WE WILL
REQUIRE THE HIGHER DEWPOINTS WITHIN THE CONVERGENCE ZONE
ASSOCIATED WITH BOUNDARY MOISTURE POOLING TO REACH THE CAPE NEEDED
FOR STORMS. THEREFORE...STORMS SHOULD HAVE A LATE START...BE
ISOLATED TO WIDELY SCATTERED IN NATURE...AND OCCUR IN A FAIRLY
NARROW ZONE ALONG AND JUST EAST OF I-75.

TONIGHT...
WITH THE LATE START TO ANY CONVECTION...WOULD ANTICIPATE THE
CELLS THAT DO DEVELOP TO LINGERING FOR A FEW HOURS PAST SUNSET.
WILL KEEP A LOW CHANCE POP IN THE FORECAST FOR THIS FAVORED
CONVERGENCE ZONE UNTIL 03Z...AND THEN ALLOW THE REST OF THE
OVERNIGHT TO BE DRY REGION-WIDE. A FEW POCKETS OF FOG ARE QUITE
LIKELY IN THE HOURS BEFORE DAWN...BUT NEITHER THE SREF OR
STATISTICAL GUIDANCE ARE SUGGESTING WE WILL HAVE ANY SIGNIFICANT
VIS ISSUES FOR THE MORNING COMMUTE. GIVEN THAT THE COVERAGE OF
RAINFALL TODAY SHOULD BE LOW...WOULD AGREE WITH THE NWP. LOW
TEMPERATURES TONIGHT WILL BE SEASONABLY WARM WITH UPPER 60S INLAND
AND LOWER 70S ALONG THE COAST.

MONDAY...
OVERALL THE SYNOPTIC PATTERN IS NOT ALL THAT DIFFERENT FROM
TODAY. THE MOST INFLUENTIAL DIFFERENCE MAY BE THAT THE MID/UPPER
LEVEL ENVIRONMENT IS SLIGHTLY MORE MOIST AND HENCE A BIT LESS
HOSTILE TOWARD DEEP CONVECTION. ALSO...THERE DOES STILL SEEM TO BE
A HINT OF THE CAPPING INVERSION IN THE FORECAST SOUNDINGS...BUT AT
LEAST FOR NOW...IT APPEARS LESS DRAMATIC. BOTH OF THESE FACTORS
SHOULD CONTRIBUTE TO A BIT HIGHER COVERAGE OF LATE DAY STORMS
ACROSS THE SAME FAVORED CONVERGENCE ZONE RUNNING ALONG AND JUST
EAST OF THE I-75 CORRIDOR. INHERITED FORECAST HAS 30-40% POPS IN
THIS ZONE...AND THEN TAPERS RAIN CHANCES BACK TO 10-20% AT THE
COAST. BASED ON THE EARLIER MEMBERS OF THE 12Z GUIDANCE CYCLE TO
ARRIVE...DO NOT SEE MUCH REASON TO MAKE SIGNIFICANT CHANGES. WILL
WAIT FOR ALL THE 12Z CONVECTION ALLOWING GUIDANCE TO ARRIVE BEFORE
MAKING A FINAL FORECAST DECISION ON TOMORROW. ANY CONVECTION ON
MONDAY WILL AGAIN BE SUPPRESSED BY THE ENVIRONMENT ALOFT UNTIL
LATE IN THE AFTERNOON OR EARLY EVENING...WHICH SHOULD AGAIN ALLOW
LOCATIONS AWAY FROM THE IMMEDIATE COAST TO PUSH 90 FOR HIGH
TEMPERATURES. AT THE BEACHES TEMPS HOLD IN THE 80S WITH THE
DEVELOPMENT ONSHORE FLOW DURING THE AFTERNOON.

ENJOY THE REMAINDER OF YOUR SUNDAY EVERYONE!

MARINE...
ATLANTIC HIGH PRESSURE WILL RIDGE ACROSS FLORIDA INTO
THE EASTERN GULF OF MEXICO THROUGH EARLY NEXT WEEK. THIS RIDGE
WILL SLIDE TO THE EAST AS A COLD FRONT ENTERS THE GULF AND MOVES
ACROSS THE FORECAST WATERS WEDNESDAY. WINDS SHIFT NORTH BEHIND
THIS FRONT AND MAY APPROACH ADVISORY LEVELS FOR A TIME WEDNESDAY
NIGHT INTO THURSDAY. HIGH PRESSURE THEN BUILDS OVER THE REGION BY
THE BEGINNING OF NEXT WEEKEND.

$$

&&

.PRELIMINARY POINT TEMPS/POPS...
TPA  73  88  74  86 /  10  20  10  20
FMY  71  89  72  88 /  20  40  20  20
GIF  71  91  71  88 /  20  30  30  40
SRQ  72  85  72  83 /  10  10  10  20
BKV  68  88  67  87 /  10  20  20  30
SPG  74  86  74  85 /  10  10  10  20

&&

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

&&

$$

SYNOPSIS/SHORT TERM/AVIATION/MARINE...14/MROCZKA


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