496
FXUS62 KTBW 050040
AFDTBW

Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
840 PM EDT Thu Sep 4 2025

...New UPDATE, AVIATION...

.UPDATE...
Issued at 835 PM EDT Thu Sep 4 2025

Quiet evening currently as afternoon and early evening convection
has largely diminished, with lingering partly cloudy skies over
the Nature Coast, and mostly cloudy skies over WC/SWFL as W/SW
flow aloft and associated mid/upper cloudiness overspreads the
peninsula north of a weak surface trough extending from the SE
Gulf across S FL into the W Atlantic. Slightly stronger E/NE
boundary layer flow expected over the peninsula on Friday will
favor a bit more Atlantic moisture advecting west across the area
and rain chances, with highest chances across SWFL extending into
parts of WCFL from mid afternoon through early evening before
diminishing. Forecast generally remains on track this evening
requiring no changes.

&&

.SHORT TERM...
(Rest of today and tonight)
Issued at 138 PM EDT Thu Sep 4 2025

An upper-level low is situated over Ontario, Canada with a longwave
trough axis stretching all the way south into the southern Gulf.
This trough axis has a slight negative tilt to it. At the base of
the trough, a disorganized area of low pressure (and thus a
trough axis) is dominating weather conditions in the eastern Gulf.
Satellite imagery shows an impressive and nearly continuous
outflow boundary that extends from just north of the Yucatan
Peninsula back to the FL Keys. This may be the remnants of the
frontal boundary that is now washed out.

In response to these features, some drier air has continued over the
northern half of the Florida peninsula. The 12Z sounding showed a
pronounced dry layer in the 550-400mb layer. However, that has since
eroded as the trough axis over the Gulf of Mexico lifts northward
somewhat. As this has taken place, convection has increased across
southern and central offshore waters, and westerly flow aloft has
carried more cloud cover over the western half of the Florida
peninsula. Thus, recent ACARS soundings from around 16Z now show
that the mid-level dry layer has largely eroded, and the overall
column moisture has increased. This setup points to a potentially
active afternoon.

The open question for the afternoon and into the evening is really
what - if any - impact this will have on convective development this
afternoon. Most of the CAMs remain fairly aggressive with
convection from the Tampa Bay Area southward. However, the cloud
cover is slowing daytime heating. Most locations have yet to reach
the 90s, even as mid-afternoon approaches. While subtle, this may
be enough to suppress activity somewhat. The rain chances for the
remainder of the day have been nudged downward in response.

&&

.LONG TERM...
(Friday through next Wednesday)
Issued at 138 PM EDT Thu Sep 4 2025

With a strong ridge parked over the Western CONUS, the longwave
trough will remain pretty well situated across the E CONUS for the
days to come. This favors maintenance of the status quo for the next
few days. The Nature Coast is favored to remain in the drier, more
stable air while SWFL remains in the humid airmass with more
frequent thunderstorms. The Tampa Bay Area and Central Florida
remain in the transition zone between both - and thus will be
favored to see some storms, but overall lower coverage than SWFL.

There are some nuances, though. With subtropical ridging trying to
build back westward, this will gradually erode the trough`s
influence across Florida. It also favors more of an easterly flow in
the days to come - favoring later timing for storms that do form.
If the sun is able to come out and the west coast sea breeze
develops, this would favor a higher concentration of storms across
the interior.

By early next week, however, a trough digs along the Pacific coast,
forcing the development of a strong ridge over the Plains, and thus
another trough over the FL peninsula. With some shortwave
perturbations propagating through the flow, this favors increasing
coverage and frequency of convection from Monday afternoon onward.
Regardless of the exact outcome, conditions will continue to feel
like late summer through the period as warm and - at the very
least - a shallow layer of moisture keeps conditions feeling
pretty close to normal for this time of year.

&&

.AVIATION...
(00Z TAFS)
Issued at 738 PM EDT Thu Sep 4 2025

Mainly VFR expected through cycle. Afternoon showers and storms
developing with chance of MVFR/LCL IFR conditions mainly from mid
afternoon through early evening. Winds light overnight then
generally easterly remainder of the cycle, with the potential for
a brief period of onshore flow in the afternoon preceding
interior convection pushing west across W FL terminals.

&&

.MARINE...
Issued at 138 PM EDT Thu Sep 4 2025

Showers and storms will continue to develop over the southern and
central waters as a weak area of low pressure remains off the FL
West Coast. As the weekend approaches, rain chances and winds begin
to decrease across coastal waters, but not completely as the flow
shifts to an easterly direction. Thunderstorms will still be
possible, especially in the evening as thunderstorms drift back
off the coast. Outside of thunderstorms, winds remain below 15
knots, keeping seas light overall through the period.

&&

.FIRE WEATHER...
Issued at 138 PM EDT Thu Sep 4 2025

While there has been some drier air aloft, especially across the
Nature Coast, low-level moisture remains sufficient to keep RH
values above critical thresholds. Additionally, some shower and
thunderstorm activity remains likely each day, especially across
central and SWFL. Fire weather concerns remain low.

&&

.PRELIMINARY POINT TEMPS/POPS...
TPA  77  92  78  91 /  20  60  20  60
FMY  76  90  76  90 /  60  70  40  70
GIF  76  92  76  92 /  20  60  10  70
SRQ  74  91  75  90 /  40  70  30  60
BKV  72  93  73  92 /  10  50  10  50
SPG  77  90  77  89 /  30  60  30  50

&&

Sea Breeze Thunderstorm Regime For Friday: 2
Sea Breeze Thunderstorm Regime For Saturday: 6

For additional information on sea breeze regimes, go to:
     https://www.weather.gov/tbw/ThunderstormClimatology

&&

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

&&

$$

UPDATE/AVIATION...Hurt
SHORT TERM/LONG TERM/MARINE/FIRE WEATHER...Flannery
DECISION SUPPORT...Oglesby
UPPER AIR/CLIMATE...Giarratana