Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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000
FXUS62 KTBW 231959
AFDTBW

ZCZC MIAWRKAFD 231920
TTAA00 KMIA DDHHMM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
355 PM EDT THU APR 23 2015

.SYNOPSIS... 19Z WATER VAPOR AND H4 RAP ANALYSIS SHOWS A COMPLEX
UPPER LEVEL PATTERN ACROSS THE CONUS. SPLIT FLOW ARRIVES OVER
NORTHERN CALIFORNIA WITH ONE BRANCH PUSHING INTO SOUTH-CENTRAL
CANADA AND ANOTHER CARVING A DEEP TROUGH THROUGH THE DESERT
SOUTHWEST/BAJA REGION. FURTHER EAST DOWNSTREAM WE FIND A DEEP AND
UNSEASONABLY COLD TROUGH IN PLACE ACROSS THE GREAT
LAKES/NORTHEASTERN STATES. SOUTHERN STREAM FLOW IS MOVING NORTH OUT
OF THE TROPICAL PACIFIC TO THE EAST OF THE BAJA TROUGH AND THEN
BECOMING MORE ZONAL AS TO MOVES OVER THE NORTH-CENTRAL GULF
COAST...INCLUDING THE FLORIDA PENINSULA.

AT THE SURFACE...A WEAK SURFACE BOUNDARY THAT SET UP ACROSS THE
NORTHEAST GULF OF MEXICO HAS BEEN THE FOCUS FOR PERSISTENT SHOWERS
AND THUNDERSTORM MOVING ASHORE TODAY. THE AREAS EFFECTED HAVE
SHIFTED THROUGH THE DAY...BUT WE HAVE NOW SEEN DECENT RAINFALL FOR
JUST ABOUT EVERYONE...WITH THE EXCEPTION OF PARTS OF LEE/CHARLOTTE
COUNTIES...AND ALSO LEVY COUNTY. THE CURRENT CONVECTIVE BAND EXTENDS
FROM THE MANATEE/SARASOTA COASTS INLAND THROUGH DESOTO AND SOUTHERN
HIGHLANDS COUNTIES. RADAR SHOWS A DEFINED OUTFLOW BOUNDARY HAS
SHIFTED SOUTH FROM THIS CONVECTIVE BAND AND APPEARS TO BE SLOWLY IN
INFLOW. CONVECTIVE ORGANIZATION AND STRENGTH OF THE CELLS HAS BEEN
ON THE DECLINE DURING THE PAST HOUR...AND EXPECT THIS TREND TO
CONTINUE INTO THE EARLY EVENING. FROM PINELLAS/HILLSBOROUGH/POLK
COUNTIES NORTHWARD THE RAINFALL HAS COME TO AN END...AND A DECENT
EVENING WEATHERWISE APPEARS IN STORE.

&&

.SHORT TERM (TONIGHT THROUGH FRIDAY)...
REST OF TODAY AND TONIGHT... BAND OF SHOWER AND ISOLATE STORMS WILL
CONTINUE TO BECOME LESS ORGANIZED INTO THE EVENING AS IT SINKS
ACROSS THE SOUTHERN HALF OF THE FORECAST AREA. HAVE HIGHEST RAIN
CHANCES SOUTH OF THE TAMPA BAY AREA...WITH LITTLE TO NO ADDITIONAL
RAINFALL EXPECTED FOR THE I-4 CORRIDOR AND NORTHWARD. ALTHOUGH
ANOTHER STRONG STORM OR TWO CAN NOT BE RULED OUT ACROSS THE SOUTHERN
HALF OF THE AREA...THE THREAT FOR SEVERE WEATHER APPEARS TO BE
RAPIDLY DECLINING AS WELL.

ONCE THIS BAND OF STORMS DISSIPATES LATER THIS EVENING...AM
ANTICIPATING A GENERALLY DRY AND SEASONABLE OVERNIGHT PERIOD AS HIGH
PRESSURE BEGINS TO BUILD IN FROM THE NORTH. THERE MAY BE A BIT OF
FOG LATE AT NIGHT ACROSS THE INTERIOR...BUT SIGNIFICANT COVERAGE OR
VISIBILITY RESTRICTIONS ARE NOT EXPECTED AT THIS TIME. LOW
TEMPERATURES TONIGHT GENERALLY IN THE 60S...WITH LOWER 70S ALONG THE
IMMEDIATE COAST FROM TAMPA BAY SOUTHWARD.

FRIDAY IS SHAPING UP TO BE A MUCH QUIETER DAY IN TERMS OF
THUNDERSTORMS. THE DEEP LAYER MOISTURE WILL HAVE BEEN SCOURED OUT
FOR THE MOST PART MAKING THE COLUMN MORE HOSTILE TOWARD DEEP
CONVECTION. IN ADDITION...MID-LEVEL TEMPS ARE FORECAST BY THE
GUIDANCE SUITE TO BE 2-3 DEGREES WARMER ON FRIDAY THAN THEY ARE
TODAY. ALL THIS SUGGESTS A GENERALLY INACTIVE SEA BREEZE
THUNDERSTORM PATTERN. HIRES GUIDANCE ENSEMBLES SUGGEST A FEW WIDELY
SCT STORMS LATE IN THE DAY ALONG THE SEA-BREEZE...GENERALLY SOUTH OF
THE TAMPA BAY AREA. WILL HAVE 20-30% POPS AFTER 19-20Z SOUTH OF
TAMPA BAY FOR THIS POTENTIAL...HOWEVER ANY STORMS SHOULD BE BRIEF IN
DURATION AND LIFE CYCLE GIVEN THE MORE HOSTILE COLUMN ALOFT.
AFTERNOON TEMPERATURES RISING WELL INTO THE 80S FOR MOST
SPOTS...WITH EVEN SOME LOWER 90S ACROSS THE SOUTHERN ZONES.

&&

.LONG TERM (SATURDAY THROUGH NEXT THURSDAY)... SAT-SUN...UPPER LEVEL
RIDGING ACROSS THE AREA FLATTENS AS A SHORT WAVE TROUGH TRACKS
ACROSS THE OHIO VALLEY AND CROSSES THE MID-ATLANTIC STATES.
MEANWHILE A FRONT SAGS IN ALONG THE GULF COAST AND THROUGH THE SE
U.S. AS IT WEAKENS...ATLANTIC HIGH PRESSURE RIDGES IN ACROSS AND
SOUTH OF THE SOUTHERN HALF OF FL.

MON-TUE...AN UPPER TROUGH/LOW MOVES OUT OF THE FOUR CORNERS REGION
TO THE EASTERN PLAINS WITH WEAK RIDGING CONTINUING ACROSS THE GULF
REGION. THE FRONT IN THE SE U.S. SETTLES INTO FL. THE ECMWF HAS A
BROAD BOUNDARY ACROSS CENTRAL FL WHILE THE GFS IS MORE CONCENTRATED
IN THE NORTHERN HALF OF THE STATE.

WED-THU...THE UPPER TROUGH BROADENS OVER THE EASTERN CONUS AS IT
DROPS DOWN INTO THE GULF THEN SLIDES EAST..MORE SLOWLY IN THE ECMWF
WHILE THE GFS IS FASTER WITH A SLIGHTLY SHARPER TROUGH. AT THE
SURFACE LOW PRESSURE MOVES EAST WITH A TRAILING COLD FRONT. HERE THE
ECMWF AND GAS ARE SIMILAR WITH THE TIMING ALTHOUGH THE ECMWF HAS THE
LOW IN THE GULF AND MOVING ACROSS FL WHILE THE GFS KEEPS THE LOW IN
THE GULF COASTAL AND SOUTHERN STATES.

EXPECT SOME LOW POPS WITH SHOWERS AND A FEW THUNDERSTORMS MAINLY
NORTH AND INTERIOR INTO EARLY MON. RAIN CHANCES THEN GRADUALLY
INCREASE THROUGH MIDWEEK WITH SOME STRONG STORMS AND HEAVY RAIN
POSSIBLE. SHOWERS AND STORMS THEN TREND DOWN FOR THE END OF THE
PERIOD. TEMPERATURES WILL START OFF ABOVE NORMAL THEN SLOWLY
DECREASE TO NEAR NORMAL...WITH THE NORTH SLIGHTLY BELOW.

&&

.AVIATION... BAND OF CONVECTION STRETCHING FROM NEAR KSRQ TO LAKE
OKEECHOBEE WILL CONTINUE TO SLOWLY SINK SOUTHWARD INTO THE EARLY
EVENING. HAVE INCLUDED VCTS FOR KPGD...BUT APPEARS UNLIKELY THIS
LINE OF STORMS WILL REACH KFMY/KRSW. NORTH OF THE BAND FOR THE I-4
CORRIDOR TERMINALS...IT APPEARS THAT THE CONVECTION HAS FINALLY COME
TO AN END. THEREFORE VIS/CIG RESTRICTIONS WILL BE POSSIBLE FOR
KSRQ/KPGD THE NEXT SEVERAL HOURS...BUT THEREAFTER WILL BE
FORECASTING VFR THROUGH REMAINDER OF THE TAF PERIOD.

&&

.MARINE... A WEAK BOUNDARY OVER THE NORTHEAST GULF OF MEXICO WEAKENS
TONIGHT AS HIGH PRESSURE ATTEMPTS TO BUILD IN FROM THE NORTH. THIS
RIDGE SLIDES SOUTH TO THE FLORIDA STRAITS BY SATURDAY. WINDS AND
WAVES ARE GENERALLY EXPECTED TO REMAIN BELOW 15 KNOTS THROUGH THE
WEEKEND.

&&

.FIRE WEATHER...
NO FIRE WEATHER CONCERNS AS RELATIVE HUMIDITY VALUES WILL REMAIN
ABOVE CRITICAL LEVELS.

&&

.PRELIMINARY POINT TEMPS/POPS...
TPA  72  87  73  87 /  10  10  10   0
FMY  73  90  73  89 /  10  30  10   0
GIF  69  88  71  89 /  20  20   0  30
SRQ  71  84  73  86 /  10  10  10   0
BKV  66  88  66  88 /  10  20   0  10
SPG  74  86  75  85 /  10  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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