Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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FXUS62 KTBW 161827
AFDTBW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
227 PM EDT TUE SEP 16 2014

...SOME LOCALLY HEAVY RAINFALL POSSIBLE TONIGHT AND WEDNESDAY...

.SHORT TERM (TONIGHT - WEDNESDAY)...
A DEEPENING UPPER TROUGH OVER THE EASTERN U.S. WITH A DIVERGENT FLOW
ALOFT COVERING THE SOUTHEASTERN U.S. AND FLORIDA WILL HELP TO INDUCE
WEAK LOW PRESSURE ALONG A SOUTHWARD SAGGING FRONTAL BOUNDARY OFF THE
SOUTHEAST U.S. COAST TONIGHT. AS THE LOW DEVELOPS AND MOVE SLOWLY
NORTHEAST OVER THE OPEN ATLANTIC SOUTHEAST OF THE MID ATLANTIC COAST
IT WILL DRAG THE TRAILING FRONTAL BOUNDARY SOUTH INTO THE NORTHERN
PENINSULA LATE TONIGHT...THEN INTO WEST CENTRAL FLORIDA DURING THE
DAY ON WEDNESDAY.

ABUNDANT MOISTURE (PW`S AOA 2 INCHES) POOLING ALONG AND AHEAD OF THE
FRONT COMBINED WITH LOW LEVEL FRONTAL CONVERGENCE...UPPER LEVEL
DIVERGENCE...AND WEAK UPPER LEVEL IMPULSES MOVING ACROSS THE REGION
WITHIN THE CYCLONIC FLOW ALOFT WILL ALL SUPPORT INCREASING RAIN
CHANCES ACROSS THE FORECAST AREA TONIGHT THROUGH WEDNESDAY WITH
SCATTERED TO NUMEROUS SHOWERS AND STORMS EXPECTED...ALONG WITH THE
POTENTIAL FOR SOME LOCALLY HEAVY RAINFALL AMOUNTS...ESPECIALLY IN
AREAS WHERE THE TRAINING OF SHOWERS AND STORMS OCCUR.

CONSIDERABLE CLOUD COVER AND INCREASING RAIN CHANCES WILL KEEP
TEMPERATURES NEAR SEASONAL NORMS WITH LOWS TONIGHT IN THE LOWER TO
MID 70S...WITH DAYTIME HIGHS ON WEDNESDAY IN THE MID TO UPPER 80S.

.LONG TERM (WEDNESDAY NIGHT - TUESDAY)...
THE LONG TERM FORECAST PERIOD WILL BEGIN WITH AN UPPER LEVEL
LONGWAVE PATTERN CONSISTING OF RIDGING OVER THE INTER- MOUNTAIN
WEST AND DOWNSTREAM TROUGHING OVER THE EASTERN CONUS. AS THE WEEK
PROGRESSES AND WE HEAD INTO THE UPCOMING WEEKEND...THE RIDGE AXIS
WILL MIGRATE EASTWARD AND SLOWLY DEAMPLIFY THE EASTERN TROUGH.
HOWEVER...GLOBAL MODELS ARE STUBBORN AND KEEP AT LEAST SOME PIECE
OF UPPER LEVEL ENERGY OVER THE FLORIDA PENINSULA. THE GFS IS MORE
ORGANIZED AND STRUCTURED WITH ITS ENERGY BEGIN A DEFINED PART OF
LEFTOVER TROUGHING ALONG THE EASTERN SEABOARD...WHILE THE ECMWF
SHOWS MORE FRACTURED...OR ENERGY LEFT BEHIND FROM THE THEN
DEPARTED TROUGH.

EITHER WAY...THE FORECAST FOR THE LATER HALF OF THE WEEK IS LOOKING
LIKE IT WILL BE A MESSY PATTERN. THIS IS NOT TO SAY THAT THE WEATHER
ITSELF WILL BE OVERLY INCLEMENT...BUT RATHER THAT FORECAST DETAILS
WILL BE MORE DIFFICULT TO COME BY...AND THEREFORE FORECAST
CONFIDENCE IS A BIT LOWER THAN AVERAGE (ESPECIALLY BEYOND FRIDAY).

FOR THURSDAY...THE FL PENINSULA IS FIRMLY UNDERNEATH THE UPPER TROUGH
WITH DEEP LAYER CYCLONIC FLOW. ANOTHER WEAK SURFACE FRONT WILL BE
MIGRATING ACROSS THE REGION...BUT AGAIN DOES NOT LOOK LIKE MUCH IN
THE WAY OF COOLER AIR WILL BE ARRIVING INTO THE REGION. A LARGE AREA
OF CONTINENTAL HIGH PRESSURE WILL BECOME ESTABLISHED OVER THE
NORTHEAST PORTION OF THE COUNTRY AND RIDGE ALL THE WAY DOWN THE
EASTERN SEABOARD INTO NORTHERN FLORIDA IN THE WAKE OF THE FRONTAL
PASSAGE.

WITHOUT A DEFINED FRONTAL PASSAGE TO CLEAR OUT THE AVAILABLE
MOISTURE...AND WILL LEFTOVER ENERGY ALOFT THROUGH MUCH OF THE
PERIOD...WILL HAVE TO KEEP SHOWER CHANCES IN THE FORECAST EACH DAY.
TOUGH TO SAY WHICH DAYS WILL SEE THE MOST SHOWER ACTIVITY AT THIS
POINT DUE TO THE ILL-DEFINED NATURE OF THE PATTERN...AND DIFFERENCES
BETWEEN THE ENSEMBLE MEMBERS THEMSELVES AS TO THE EXACT EVOLUTION OF
THE UPPER TROUGH. WITHOUT ANY ABNORMAL HEIGHTS...OR CLOUDY/WASHOUT
DAYS EXPECTED...WILL KEEP TEMPERATURES NEAR CLIMO THROUGH THE
UPCOMING WEEKEND AND FOR NOW KEEP SHOWER CHANCES CONSERVATIVE.
HOPEFULLY A MORE DEFINED PATTERN BETWEEN THE MEMBERS WILL EMERGE IN
THE NEXT DAY OR TWO.

&&

.AVIATION...
DEVELOPING SHRA/TSRA MAY BRING BRIEF MVFR/IFR CONDITIONS TO THE
TERMINALS DURING THE TAF FORECAST PERIOD AND HAVE HANDLED WITH
VCTS FOR NOW WITH POSSIBLE BRIEF TEMPO GROUPS BEING ADDED TO ANY
AMENDMENTS AS NEEDED. OUTSIDE OF THE CONVECTION VFR WILL PREVAIL.
WEST WINDS IN THE 6 TO 8 KNOT RANGE IS EXPECTED WITH HIGHER GUSTS
IN THE VICINITY OF TSRA.

&&

.MARINE...
INTERACTION BETWEEN HIGH PRESSURE OVER SOUTHERN FLORIDA AND A
FRONTAL BOUNDARY EXTENDING ACROSS NORTHERN FLORIDA AND THE NORTHERN
GULF OF MEXICO WILL PRODUCE A WESTERLY WIND FLOW THROUGH WEDNESDAY.
NUMEROUS THUNDERSTORMS AND RAIN SHOWERS ASSOCIATED WITH THIS FRONT
CAN BE EXPECTED OVER THE NORTHERN WATERS TODAY AND MOVING SOUTHWARD
LATER TODAY AND ON WEDNESDAY. GUSTY WINDS...HEAVY RAINFALL AND
DANGEROUS CLOUD TO WATER LIGHTNING CAN BE EXPECTED WITH THESE
STORMS. CONDITIONS WILL IMPROVE ON THURSDAY WITH DECREASING NORTH
NORTHWEST WINDS...THEN VEERING AROUND TO THE EAST ON FRIDAY. A MORE
TYPICAL SUMMERTIME PATTERN WILL SETUP ON THE WEEKEND WITH AFTERNOON
AND EVENING STORMS OVER THE COASTAL WATERS.

&&

.FIRE WEATHER...
AMPLE MOISTURE AND RAIN CHANCES WILL KEEP HUMIDITY VALUES WELL
ABOVE CRITICAL LEVELS THE REMAINDER OF THE WEEK WITH NO FIRE WEATHER
ISSUES EXPECTED.

&&

.PRELIMINARY POINT TEMPS/POPS...
TPA  75  88  75  90 /  70  60  30  20
FMY  75  88  73  90 /  30  70  50  40
GIF  73  87  72  90 /  70  60  30  30
SRQ  75  86  76  90 /  60  70  40  20
BKV  71  88  68  90 /  70  50  20  20
SPG  78  87  77  89 /  70  60  30  20

&&

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

$$

SHORT TERM/AVIATION/FIRE WEATHER...57/MCMICHAEL
LONG TERM...14/MROCZKA
MARINE...74/WYNN
DECISION SUPPORT...63/JILLSON




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