Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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FXUS62 KTBW 230813
AFDTBW

Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
413 AM EDT Wed Aug 23 2017

.SHORT TERM (Today - Thursday)...
Aloft - a somewhat fractured ridge stretches westward from northwest
Mexico...along the Gulf coast...to Atlantic waters off the southeast
U.S. On the south of this ridge a low was on the northeast corner of
the Yucatan Peninsula while an inverted trough/tropical wave was
between the southeast FL coast and the Bahamas. With time the ridge
weakens and separates as the low moves toward the lower Rio Grade
Vally and the trough slides north along eastern FL. Surface -
Atlantic high pressure extending along Latitude 30 North to the
upper TX coast gradually pulls back into the Atlantic...as the
surface reflection of the Yucatan upper low moves into the west-
central Gulf and the tropical wave shifts across southern FL then
eases northward while remaining disorganized.

The inverted trough/tropical wave will provide increasing moisture
and a prevailing easterly flow across the area. Model PWAT values
range from 1.5 to around 2 inches through tonight to 2  to 2.5
inches for Thu...from north to south. The pressure gradient will
be relaxed enough to allow sea breezes to shift the flow to
onshore in the afternoons...however staying close to the coast.
The additional moisture along with the trough/wave and the sea
breezes near the coast will support scattered to locally numerous
showers and thunderstorms this afternoon and again Thu...along
with some widespread coverage late Thu. The shower and storm
chances will be the highest in the south and trend down going
north. Temperatures run on the warm side of normal although highs
Thu may dip a degrees or two compared to today

.MID TERM/LONG TERM (Thursday Night-Tuesday)...
Tropical wave will linger in the vicinity of the Florida peninsula
Thursday night into Saturday then gets picked up by a trough moving
across the eastern U.S. Sunday as a cold front settles into the
southeast states. The exact location and timing of the wave
continues to vary between the global models, but in general we will
see deep moisture across the region through Saturday and this
combined with daytime heating and the sea breezes will lead to 50%
to 70% rain chances.

For Sunday through Tuesday the global models try to develop the wave
as it moves northeast off the southeast U.S. coast while taking the
remnants of Harvey northeast from Texas into the Lower Mississippi
Valley. The timing and location of these features continues to vary
a lot between the models and from model run to model run so for now
have gone with a blend which would bring some drier air south into
the region as northeast flow increases Sunday into Monday with PoPs
ranging from about 30 to 50 percent on these days. By Tuesday the
flow should back around to the south and southwest as whatever is
left of Harvey moves into the Lower Mississippi Valley and will
still have enough moisture across the area to see scattered showers
and thunderstorms. Similar to yesterdays thinking this scenario
could change substantially depending on the strength and location of
the features early next week.

Daytime high temperatures will be near to slightly below normal with
overnight lows near to slightly above normal through the period.

&&

.AVIATION...
23/06Z TAFs. Prevailing VFR expected through the TAF period...however
VCTS with FEW-SCT CB BTWN 18Z-03Z may provide brief MVFR/LCL IFR
late in the period. Light and variable/easterly winds for the rest
of tonight pick up some from the E or SE in the morning and
continue. Although TPA/PIE/SRQ may bay-sea breeze.

&&

.MARINE...
Relaxed pressure gradient remains in place as a tropical wave
moves into south FL and tracks north...deepening over southeast
U.S. coastal waters during the weekend as high pressure from the
north build int0 the eastern Gulf. Winds run 15 knots or less
expect locally higher near scattered to at times numerous
thunderstorms.

&&

.FIRE WEATHER...
A moist airmass will preclude any low humidity concerns and provide
daily showers and thunderstorms.

&&

.Preliminary Point Temps/PoPs...
TPA  93  79  91  78 /  40  30  70  40
FMY  90  76  89  77 /  70  30  70  50
GIF  93  76  92  75 /  50  20  60  30
SRQ  92  77  90  78 /  50  40  60  40
BKV  95  75  93  75 /  20  30  60  30
SPG  92  79  90  79 /  40  40  60  40

&&

.TBW WATCHES/WARNINGS/ADVISORIES...
FL...None.
Gulf waters...None.
&&

$$

SHORT TERM/AVIATION/MARINE/FIRE WEATHER...09/Rude
MID TERM/LONG TERM/DECISION SUPPORT...69/Close



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