Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KTBW 031538
AFDTBW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
1138 AM EDT FRI JUL 3 2015

.SYNOPSIS...
15Z WATER VAPOR AND H4 RAP ANALYSIS CONTINUE TO SHOW AN UPPER
LEVEL PATTERN CONSISTING OF BROAD RIDGING ACROSS THE INTER-
MOUNTAIN WEST...FOLLOWED DOWNSTREAM BY LONGWAVE TROUGHING FROM THE
CENTRAL PLAINS TO THE EASTERN CONUS. THE INFLUENCE OF THIS TROUGH
DOES NOT QUITE REACH SOUTH FAR ENOUGH TO HAVE A SIGNIFICANT IMPACT
ON OUR COLUMN...WITH MOST OF THE SYNOPTIC SUPPORT FOR LIFT
REMAINING NORTH OF THE I-10 CORRIDOR. IN FACT BELOW THE 400MB
LEVEL WE FIND A NARROW SWATH OF RIDGING ALOFT EXTENDING OVER THE
FL PENINSULA AND EASTERN GULF.

FROM A MOISTURE PERSPECTIVE...THE ATMOSPHERIC COLUMN ACROSS THE
ENTIRE FORECAST AREA IS QUITE MOIST BELOW THE H5 LEVEL...AND THEN
DRIES OUT CONTINUING UPWARD. HOWEVER...JUDGING BY
EXPERIENCE...THE DEGREE OF DRY AIR DOES NOT APPEAR SUFFICIENT TO
HAVE A SIGNIFICANT IMPACT ON THE EVENTUAL COVERAGE OF SHOWERS AND
STORMS THIS AFTERNOON/EARLY EVENING.

LOOKING CLOSER AT THE 12Z KTBW SOUNDING FROM A CONVECTIVE
PERSPECTIVE...SOME OF THE VARIABLE SEEN IN PREVIOUS DAYS THAT HAVE
ENHANCED THE THREAT FOR HAIL WITH THE LATE DAY STORMS ARE STILL
BEING SAMPLED THIS MORNING...WHILE OTHERS ARE NOT. THE H5
TEMPERATURES AROUND THE H5 LEVEL ARE BETWEEN -8C TO -10C. THESE
VALUES ARE ON THE COOL SIDE FOR JULY AND HAVE BEEN CONTRIBUTING TO
SOME DECENT MID-LEVEL LAPSE RATES. ON THE OTHER HAND...THE LAPSE
RATES BELOW H5 ARE NOT QUITE AS IMPRESSIVE AS PREVIOUS
DAYS...WHICH MIGHT LIMIT THE POTENTIAL FOR UPDRAFT STRENGTH. ALSO
EVALUATING THE VARIOUS BUFKIT SOUNDING PROFILES...SHOWS A
NOTICEABLE DECREASE IN FORECAST CAPE WITHIN THE -10C TO -30C HAIL
GROWTH ZONE. IN THE END...WOULD SAY THE COLUMN IS SLIGHTLY MORE
FAVORABLE BY CLIMO FOR HAIL UP TO QUARTER SIZE DUE TO THE BELOW
NORMAL TEMPS IN THE MID-LEVELS...BUT OVERALL THE THREAT APPEARS
LOWER THAN THE PAST COUPLE OF DAYS. THAT BEING SAID...GIVE THE
RIGHT UPDRAFT...A LITTLE ROTATION IN THE MID-LEVELS...AND THE
HYDROSTATIC PRESSURE GRADIENT FORCE CAN OVERWHELM ANY NEGATIVES IN
THE COLUMN. SO...SHOULD HAVE A HARDER TIME PRODUCE SEVERE
HAIL...BUT AS ALWAYS WILL NEED TO MONITOR RADAR TRENDS AND TAKE IT
ONE STORM AT A TIME.

CLOSER TO THE SURFACE...THE SUBTROPICAL RIDGE AXIS LIES RIGHT
THROUGH THE CENTER OF THE STATE AND OUT ACROSS THE EASTERN GULF
OF MEXICO.

&&

.SHORT TERM (REST OF TODAY THROUGH SATURDAY)...
NOT MUCH HAS CHANGED IN THE LOW LEVEL PATTERN SINCE THURSDAY.
THIS RIDGE WILL KEEP THE BEST SEA BREEZE FOCUS FOR ASCENT WITHIN
THE SOUTHEASTERLY SYNOPTIC FLOW TO THE SOUTH OF THE RIDGE AXIS
ACROSS OUR SOUTHERN ZONES. THE HIGHEST POPS WILL AGAIN FALL ACROSS
THIS REGION...BUT HOLD OFF UNTIL LATE IN THE AFTERNOON AND EARLY
EVENING. EARLIER SCT CONVECTION THROUGH THE EARLY AND MIDDLE
AFTERNOON IS MORE LIKELY ACROSS THE NATURE COAST/I-4 CORRIDOR
ZONES ASSOCIATED WITH THE MORE RAPID INLAND PROPAGATION OF THE
SEA-BREEZE. EXPECT TO SEE THE FIRST STORMS START TO FIRE BETWEEN
16-17Z...VERY SIMILAR TO PREVIOUS DAYS...AND IN AGREEMENT WITH
MANY OF THE CONVECTION ALLOWING HIRES ENSEMBLE MEMBERS.

HEADING INTO THE EVENING...THERE IS A TREND IN THE LATEST GUIDANCE
TO TRY AND BRING CONVECTION BACK NORTHWARD TOWARD THE TAMPA BAY
AREA...MAINLY ASSOCIATED WITH NW PROPAGATING OUTFLOW BOUNDARIES
FROM THE STORMS OVER THE SOUTHERN FORECAST AREA. NOT COMPLETELY
READY TO COMMIT TO THIS SCENARIO...BUT WILL LEAVE CHANCE POPS IN
THE GRIDS THROUGH THE MID EVENING FOR THE I-4 CORRIDOR...AND VCTS
IN THE ASSOCIATED TAFS. WILL MONITOR FUTURE RUNS OF THE HRRR AND
SEE IF THIS TREND CONTINUES ONCE THE FIRST STORMS OF THE DAY
DEVELOP AND ARE INCORPORATED INTO THE SIMULATIONS.

EVENING STORMS SHOULD HAVE DISSIPATED BY 03-04Z...FOLLOWED BY A
DRY OVERNIGHT ACROSS THE LAND MASS. LATE TONIGHT AS THE LAND
BREEZE BECOMES MORE DEFINED...A SCATTERING OF STORMS OVER THE
NEAR SHORE MARINE ZONES CAN BE EXPECTED.

FOR THE 4TH...THE RIDGE AXIS AT THE SURFACE LOOKS TO BECOME QUITE
BROAD...RESULTING IN A GENERAL LIGHT SOUTHEAST TO SOUTH FLOW
REGIME FROM SOUTH TO NORTH ACROSS THE FORECAST AREA. THIS IS A
GENERALLY MOIST FLOW REGIME...AND WITH NO SIGNIFICANT HOSTILE
LAYERS IN THE COLUMN FOR DEEP CONVECTION...WOULD EXPECT SCT-NMRS
STORMS TO BE IN THE FORECAST FOR MOST ZONES. WITH TIME...SEA-
BREEZE BOUNDARIES WILL PUSH INLAND...SO THE LATER IN THE DAY WE
GO...THE MORE NUMEROUS STORM COVERAGE SHOULD BE AWAY FROM THE
COAST. HOWEVER...WITH LITTLE IN THE WAY OF WESTERLY FLOW...
CONVECTIVE OUTFLOW BOUNDARIES THAT MOVE WEST FROM INLAND CONVECTION
WILL HAVE LITTLE OPPOSITION...AND COULD CERTAINLY BRING A ROUND
OF STORMS BACK TOWARD PORTIONS OF THE COAST FOR THE EVENING. SUCH
IS SUMMER CONVECTION IN FLORIDA. THE LOW LEVEL PATTERN OFTEN GIVES
A GOOD FIRST GUESS AS TO WHERE THE BEST CHANCE FOR STORMS WILL
BE...BUT "UNEXPECTED" OUTFLOW BOUNDARIES ON A GIVEN DAY CAN
QUICKLY RUIN A WELL THOUGHT OUT FORECAST.

&&

.LONG TERM (SATURDAY NIGHT-FRIDAY)...
MESO SCALE TO DOMINATE THE FORECAST WITH A VENGEANCE. LONG WAVE
TROUGH OVER EASTERN HALF OF COUNTRY WEAKENS AS NORTHERN STREAM
MOVES AWAY AND LEAVES WEAK TROUGHINESS IN SOUTHEAST U.S. AND
NORTHEAST GULF INTO EARLY NEXT WEEK. BOTH THE GFS AND ECMWF BRING
AN UPPER LEVEL TUTT INTO THE BAHAMAS LATE NEXT WEEK. ALL THIS
MEANS WEAK SURFACE PRESSURE AND SEA BREEZE ACTIVITY THROUGH THE
EXTENDED. STORMS WILL BE SLOW MOVING DUE TO WEAK WINDS ALOFT. USED
CONSENSUS OF MODELS FOR POPS (WITHOUT SREF) WHICH MEANS 40-50
PERCENT CHANCE OF STORMS EACH DAY. OVERNIGHT LOWS WILL BE A FEW
DEGREES ABOVE NORMAL AND DAYTIME HIGHS AROUND NORMAL.

&&

.AVIATION...
VFR CONDITIONS PREVAIL ACROSS THE REGION LATE THIS MORNING.
SCATTERED STORMS WILL BEGIN TO DEVELOP AROUND MIDDAY...WITH STORMS
PEAKING IN COVERAGE DURING THE LATER AFTERNOON AND EVENING BETWEEN
KPGD AND KFMY/KRSW. OUTSIDE OF THE SCATTERED TO NUMEROUS
STORMS...VFR CONDITIONS WILL BE THE GENERAL RULE. STORMS DISSIPATE
WITHIN A FEW HOURS OF SUNSET...WITH VFR CONDITIONS REGION-WIDE
THROUGH THE OVERNIGHT AND SATURDAY MORNING.

&&

.MARINE...
THE SUBTROPICAL RIDGE AXIS WILL REMAIN PARKED OVER THE EASTERN
GULF OF MEXICO THROUGH THE UPCOMING HOLIDAY WEEKEND KEEPING WINDS
AND SEAS LOW OUTSIDE OF TYPICAL SCATTERED THUNDERSTORM ACTIVITY.
THE BEST CHANCES FOR THUNDERSTORM ACTIVITY WILL BE DURING THE
LATE NIGHT AND MORNING HOURS EACH DAY...ALTHOUGH BOATERS WILL NEED
TO BE AWARE OF POSSIBLE STORMS MIGRATING OFFSHORE DURING THE LATE
AFTERNOON TO THE SOUTH OF TARPON SPRINGS.

&&

.FIRE WEATHER...
HIGH PRESSURE WILL HOLD OVER THE REGION THROUGH THE HOLIDAY
WEEKEND. TYPICAL SUMMER CONDITIONS ARE EXPECTED WITH SCATTERED
MAINLY AFTERNOON AND EVENING THUNDERSTORMS EACH DAY WITH ABOVE
NORMAL TEMPERATURES. NO FIRE WEATHER HAZARDS EXPECTED AS RELATIVE
HUMIDITY VALUES ARE FORECAST TO REMAIN ABOVE CRITICAL LEVELS
EACH DAY.

FOG IMPACT...NO WIDESPREAD FOG IMPACTS ARE EXPECTED OVER THE NEXT
SEVERAL DAYS.

&&

.PRELIMINARY POINT TEMPS/POPS...
TPA  94  78  92  78 /  30  20  40  30
FMY  95  76  94  76 /  60  30  60  30
GIF  96  76  95  75 /  40  20  60  50
SRQ  94  77  92  77 /  30  20  40  20
BKV  95  73  93  73 /  30  20  40  30
SPG  94  80  92  80 /  30  20  30  20

&&

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

&&

$$

SYNOPSIS/SHORT TERM/AVIATION/MARINE/FIRE WEATHER...MROCZKA
LONG TERM...NOAH
DECISION SUPPORT...FLEMING


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.