Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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000
FXUS62 KTBW 220026
AFDTBW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
720 PM EST FRI NOV 21 2014

.UPDATE (REST OF TONIGHT AND SATURDAY)...
00Z WATER VAPOR AND H4 RAP ANALYSIS SHOWS SPLIT FLOW ARRIVING ALONG
THE PACIFIC NORTHWEST COAST...WITH ONE BRANCH REMAINING ZONAL IN
NATURE ACROSS THE NORTHERN ROCKIES/NORTHERN PLAINS...WHILE THE OTHER
BRANCH DIVES SOUTHWARD INTO A POTENT AND ENERGETIC SHORTWAVE TROUGH
EJECTING EASTWARD ACROSS THE 4-CORNERS REGION OF THE SOUTHWEST. THE
FLOW DOWNSTREAM OF THIS SHORTWAVE ALONG THE NORTHERN GULF COAST IS
BECOME EVER-MORE RIDGED/ANTI-CYCLONIC IN NATURE IN RESPONSE TO THE
HEIGHT FALLS BEGINS TO SPREAD INTO THE SOUTHERN PLAINS. THE
SHORTWAVE IS PROGGED BY ALL RELIABLE NWP GUIDANCE TO QUICKLY
TRANSLATE EASTWARD TO THE NORTHERN GULF COAST THIS WEEKEND AND ITS
INFLUENCE...OR AT LEAST FRINGE INFLUENCES...WILL BE THE DOMINANT
WEATHER PLAYER IN OUR FORECAST FOR BOTH SATURDAY AND SUNDAY.
SOUTHERN STREAM IS CURRENTLY CUTTING ACROSS THE SOUTHERN GULF AND
SOUTHERN FLORIDA PENINSULA RESULTING IN A WELL DEFINED UPPER LEVEL
MOISTURE GRADIENT ALONG AND JUST NORTH OF THE I4 CORRIDOR THIS
EVENING.

LOWER LEVELS...FLORIDA PENINSULA RESIDES WITHIN A MODERATE EASTERLY
FLOW AROUND THE SOUTHERN PERIPHERY OF STRONG 1035MB CONTINENTAL HIGH
PRESSURE CENTERED OVER VIRGINIA. WEAK ISENTROPIC UPGLIDE BETWEEN THE
295-305K SURFACES OVER THE SOUTHERN HALF OF THE FL PENINSULA IS
PROVIDING ENOUGH LIFT TO SUPPORT THE OVERCAST CANOPY AND SCT LIGHT
SHOWERS/SPRINKLES SEEN ON REGIONAL RADARS TO THE SOUTH OF I-4.

REST OF TONIGHT...GFS/NAM/RAP ALL IN AGREEMENT SHOWING FURTHER
ENHANCEMENT AND NORTHWARD EXPANSION TO THE UPGLIDE REGIME...WITH A
GRADUAL MOISTENING / CONDENSATION PRESSURE DEFICIT REDUCTION TO THE
EFFECTED LAYERS. WITH THIS IN MIND WOULD EXPECT THE OVERCAST
CONDITIONS AND SHOWER CHANCES TO ALSO INCREASE AND SPREAD NORTHWARD
WITH TIME. ANY SHOWERS WILL STILL LIKELY BE VERY LIGHT AND NOT
ANTICIPATING MUCH RAINFALL ACCUMULATION...BUT POTENTIALLY ENOUGH TO
DAMPEN SOME OUTDOOR ACTIVITIES...ESPECIALLY SOUTH OF TAMPA BAY.
TEMPERATURES WILL ONLY SLOWLY FALL DURING THE OVERNIGHT...AND DO NOT
EXPECT MUCH OF A SWING BETWEEN NOW AND SUNRISE IN MOST LOCATIONS.

SATURDAY...
UPPER LEVEL ENERGY WILL BEGIN TO EJECT OUT OVER THE GULF OF MEXICO
THROUGH THE DAY. A SURFACE REFLECTION WARM FRONTAL FEATURE IS
EXPECTED TO ORGANIZE AND EXTEND EASTWARD TO THE SOUTHERN
PENINSULA...AND THEN BEGIN LIFTING SLOWLY NORTHWARD THROUGH THE DAY.
LATEST GUIDANCE RUNS ARE BECOMING SLOWER WITH THE NORTHWARD
ADVANCEMENT OF THIS WARM FRONT...AND THE FIRST DAY OF THE WEEKEND IS
LOOKING MORE CLOUDY AND SHOWERY FOR THE MAJORITY OF THE AREA WITH
TIME. STEADY AND PERSISTENT UPGLIDE AND A MOIST LOWER 10-15KFT OF
THE ATMOSPHERE SHOULD SUPPORT OFF AND ON LIGHT SHOWERS. THE
POTENTIAL FOR SOME HEAVIER SHOWERS SHOULD BEGIN SATURDAY AFTERNOON
ACROSS THE SOUTHERN HALF OF THE AREA THROUGH A COMBINATION OF
UPGLIDE AND A FEW HUNDRED J/KG OF MIXED LAYER CAPE. HOWEVER...THE
SLOWER FRONTAL ADVANCEMENT MAY KNOCK SOME OF THIS POTENTIAL LOWER
LEVEL CAPE DOWN IN FUTURE MODEL RUNS. EITHER WAY...SHOWALTER INDICES
ARE AROUND ZERO FOR MUCH OF THE AREA SATURDAY AFTERNOON...
INDICATING AT LEAST SOME POTENTIAL FOR ELEVATED
INSTABILITY/CONVECTION. HAVE EXPANDED THE AREA OF ISOLATED THUNDER
IN THE GRIDS NORTHWARD INTO THE NATURE COAST TO COINCIDE WITH THESE
SHOWALTER INDICES. CURRENT HIGH TEMPERATURE GRID IS LIKELY MORE
REPRESENTATIVE OF THE EARLIER FRONTAL PASSAGE FOR THE SOUTHERN ZONES
EXPECTED WITH PREVIOUS MODEL RUNS. IF THE SLOWER TREND ENDS UP
VERIFYING...THEN LOWER 80S SOUTH OF TAMPA BAY...MAY BE A BIT
OPTIMISTIC. WILL NOT MAKE TO MANY SIGNIFICANT CHANGES FOR NOW AND
ALLOW THE OVERNIGHT SHIFT TO EVALUATE IF THE SLOWER TREND AND HENCE
COOLER TEMPERATURES STILL LOOK VALID.

&&

.LONG TERM /SATURDAY NIGHT-FRIDAY/...
MODEL SOLUTIONS ARE IN FAIRLY GOOD AGREEMENT THROUGH THE LONG TERM
PERIOD. DURING SATURDAY NIGHT AND SUNDAY A MID/UPPER LEVEL TROUGH
WILL BE MOVING ACROSS THE LOWER MISSISSIPPI VALLEY AND INTO THE
TENNESSEE AND OHIO VALLEYS WITH SOME SHORTWAVE ENERGY TRAILING SOUTH
INTO THE GULF OF MEXICO. THIS WILL DRIVE THE DEVELOPING WARM FRONT
NORTHWARD THROUGH THE REGION SATURDAY NIGHT...WHILE A WEAKENING COLD
FRONT MOVES INTO THE SOUTHEAST STATES. THE WARM FRONT WILL THEN
REMAIN JUST NORTH OF THE FORECAST AREA ON SUNDAY. THE BEST RAIN
CHANCES WILL REMAIN OVER THE NATURE COAST WHERE THE DEEPEST MOISTURE
AND BEST FORCING FOR ASCENT WILL RESIDE. QUITE A WARM AND MOIST
AIRMASS WILL BE MOVING INTO THE REGION SATURDAY NIGHT AND
SUNDAY...SO WILL MENTION BOTH SHOWERS AND THUNDERSTORMS IN THE
FORECAST. ADDITIONALLY...THE STORM PREDICTION CENTER HAS NATURE
COAST LOCATIONS OUTLOOKED FOR A SLIGHT RISK OF SEVERE THUNDERSTORMS
SATURDAY NIGHT AND SUNDAY. AT THIS POINT IT APPEARS THAT THE MAIN
THREAT WILL BE ISOLATED TORNADOES AND DAMAGING WINDS SATURDAY NIGHT
AND THEN DAMAGING WIND POTENTIAL ON SUNDAY.

EARLY NEXT WEEK A DEEPENING TROUGH WILL DEVELOP OVER THE CENTRAL
U.S. AND MOVE EASTWARD INTO THE EASTERN STATES DURING MIDWEEK.
THIS WILL HELP TO DRIVE THE COLD FRONT OVER THE SOUTHEAST STATES
INTO THE REGION DURING TUESDAY AND EXITING THE AREA BY WEDNESDAY.
FOR MONDAY AND MONDAY NIGHT SOUTH TO SOUTHWEST WINDS WILL CONTINUE
TO BRING MOISTURE NORTHWARD WITH A CHANCE OF SHOWERS AND
THUNDERSTORMS...ESPECIALLY ACROSS THE NATURE COAST CLOSEST TO THE
SLOW MOVING COLD FRONT/TROUGH. DURING TUESDAY AND TUESDAY NIGHT THE
FRONT WILL MOVE SOUTHWARD THROUGH THE REGION AND WITH PLENTY OF
MOISTURE IN PLACE WE SHOULD SEE SCATTERED TO NUMEROUS SHOWERS AND A
FEW THUNDERSTORMS. A FEW SHOWERS MAY LINGER WEDNESDAY AS THE
MID/UPPER LEVEL TROUGH AXIS SWINGS ACROSS AREA...OTHERWISE SOME
COOLER AND DRIER AIR WILL RETURN.

TEMPERATURES THROUGH MONDAY NIGHT WILL GENERALLY BE ABOVE NORMAL
WITH DAYTIME HIGHS CLIMBING INTO THE UPPER 70S TO MID 80S AND LOWS
IN THE 60S TO LOWER 70S. ALONG WITH THE ABOVE NORMAL TEMPERATURES
WILL COME INCREASED HUMIDITY WITH DEW POINTS CLIMBING BACK INTO THE
60S AND LOWER 70S. FOR TUESDAY AND TUESDAY TEMPERATURES WILL BE NEAR
TO A FEW DEGREES BELOW NORMAL WITH HIGHS IN THE UPPER 60S TO NEAR 80
DEGREES AND LOWS IN THE UPPER 40S TO AROUND 60. FOR WEDNESDAY
THROUGH FRIDAY EXPECT BELOW NORMAL TEMPERATURES TO RETURN WITH
HIGHS MAINLY IN THE 60S AND LOWS MOSTLY IN THE 40S.

&&

.AVIATION...
SKIES ARE NOW OVERCAST ACROSS WEST-CENTRAL AND SOUTHWEST FLORIDA AND
WILL REMAIN SO FOR THE BULK OF THE TAF PERIOD. CEILINGS ARE STILL
ABOVE VFR CONDITIONS FOR ALL TERMINALS BUT WILL BE LOWERING THROUGH
THE OVERNIGHT HOURS...ALONG WITH SCT LIGHT SHOWERS AND SPRINKLES.
THE RAINFALL SHOULD NOT BE HEAVY ENOUGH FOR ANY VISIBILITY
RESTRICTIONS. LATE TONIGHT AND INTO THE DAY ON SATURDAY...A WARM
FRONT WILL LIFT INTO THE REGION PROVIDING GOOD CHANCES FOR PERIODS
OF MVFR CEILINGS FOR ALL TERMINAL. SHOWER COVERAGE IS ALSO LIKELY TO
INCREASE THROUGH THE DAY WITH BETTER CHANCES FOR A FEW HEAVY
DOWNPOURS BY THE AFTERNOON HOURS.

&&

.MARINE...
A TIGHT PRESSURE GRADIENT BETWEEN STRONG SURFACE HIGH PRESSURE TO
THE NORTH AND A STALLED FRONTAL BOUNDARY OVER SOUTHERN FLORIDA
CONTINUES TO PRODUCE GUSTY EAST NORTHEAST WINDS ACROSS THE COASTAL
WATERS. CONDITIONS WILL REACH SMALL CRAFT ADVISORY LEVEL OVER THE
OUTER WATERS. WINDS WILL REMAIN GUSTY WITH SMALL CRAFT EXERCISE
CAUTION CONDITIONS ACROSS ALL COASTAL WATERS THROUGH THE WEEKEND.
THE WINDS WILL VEER TO THE SOUTH SOUTHEAST AND RAIN CHANCES WILL
INCREASE ON SATURDAY AND SUNDAY AS AN AREA OF LOW PRESSURE MOVES
NORTH OF THE AREA. THE COLD FRONT ASSOCIATED WITH THIS LOW IS
EXPECTED TO MOVE THROUGH THE COASTAL WATERS LATE MONDAY INTO
TUESDAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
TPA  62  79  68  81 /  30  40  50  30
FMY  65  82  70  85 /  40  40  30  30
GIF  62  77  67  83 /  30  40  50  40
SRQ  62  82  70  83 /  30  40  40  30
BKV  57  77  70  82 /  20  40  60  50
SPG  63  78  69  81 /  30  40  50  30

&&

.TBW WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GULF WATERS...SMALL CRAFT ADVISORY UNTIL 1 AM EST SATURDAY FOR
     BONITA BEACH TO ENGLEWOOD OUT 20 TO 60 NM-ENGLEWOOD TO
     TARPON SPRINGS OUT 20 TO 60 NM-TARPON SPRINGS TO
     SUWANNEE RIVER OUT 20 TO 60 NM.

&&

$$

UPDATE/AVIATION...MROCZKA
LONG TERM/DECISION SUPPORT SERVICES...21/JELSEMA
MARINE...11/MCKAUGHAN




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