Tornado in Florida, July 20, 2024

Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
244 PM EDT Sat Jul 20 2024

...New DISCUSSION, MARINE, FIRE WEATHER...

.DISCUSSION...
Issued at 243 PM EDT Sat Jul 20 2024

Recent surface analysis shows the position of the Atlantic ridge
axis is across the central Florida peninsula and this will allow for
a more progressive west coast sea breeze across the Nature Coast as
it spreads further inland with the more southwesterly low level flow
there. Conversely, a more southeast flow particularly south of I-4
will keep the sea breeze collision closer to the western side of the
peninsula and as a result, scattered to numerous showers and storms
will develop late afternoon and evening with the greatest coverage
expected to be along/near the I-4 corridor around Polk/Sumter
counties southward into southwest Florida where activity there
should be a bit closer to the coast. In these areas, PoPs are in the
65%-80% range and areas a bit closer to the coast across west
central Florida will be peak around 40%-60%. Given the moist
atmospheric environment with PWATs around 2" or so and slow storm
motions to the N-NE, locally heavy rainfall and minor flooding will
be the main concern, particularly in poor drainage areas but
occasional generally sub-severe wind gusts will also be possible.
Otherwise, any of the convection that develops will follow the
typical diurnal trend and taper off by mid to late evening with the
loss of heating as temperatures fall to mid/upper 70s overnight.

There will be a slight shift northward of the Atlantic ridge axis
into Sunday as ridging aloft builds in from the east and this will
support southeasterly flow for most of the region. Climatologically,
this pattern would generally favor a sea breeze collision along the
western side of the peninsula, which of course would typically
result in highest precipitation coverage during late afternoon and
evening hours. While another round of convection is expected to
occur tomorrow, one limiting factor that is expected to decrease the
overall coverage will be the addition of dust from the Saharan
Air Layer (SAL). Although some minor concentrations of this dust
is already evident across portions of the peninsula on satellite
imagery, there are currently higher concentrations moving
northwestward across the Bahamas and portions the Caribbean and
this area of dust will advect across our area overnight into
Sunday. The effects of this can be easily seen in PWAT forecast
data for Sunday as models show a ribbon of lower values spreading
across central Florida during the late afternoon and evening,
which should have at least some impact on overall precipitation
coverage as the drier air mass will move through during peak
heating hours. That said, it won't be a completely dry day by any
means as the sea breeze collision along the Florida west coast
will support at least some scattered activity with the best rain
chances expected to occur in two separate regions with the first
being southwest FL and the other being the Nature Coast. In
between these two regions, there will be a corridor of lower
PWATs associated with the SAL so some minor decrease in overall
coverage could occur but again, not dry by any means.

As the new work week begins, there will be a surge in tropical
moisture with widespread PWATs over 2 inches as a tropical waves
passes through. This will yield likely PoPs on Monday and Tuesday
with a continued southeasterly flow regime as Atlantic high
pressure continues to dominate. By the middle of the week, there
may be another round of dust from the SAL that pivots through with
models showing at least some lowering of PWAT values but once
again, it doesn't appear this dust will be enough to completely
remove precipitation chances as additional diurnal sea breeze
showers and storms are expected to continue but coverage may
decrease somewhat. However, by the end of the week, it appears
that deeper moisture will quickly spread back into the region as a
Tropical Upper Tropospheric Trough (TUTT) moves across the
Bahamas late week and eventually towards the Florida peninsula.
While the timing, location, and strength of this feature still
remains uncertain at this time, additional upper support and
moisture could yield elevated rain chances late in the week and
into next weekend.

&&

.AVIATION...
(18Z TAFS)
Issued at 144 PM EDT Sat Jul 20 2024

Convection has begun this afternoon as the sea breeze pushes
inland and precipitation coverage will increase by this evening as
the sea breeze collision occurs. As a result, VCTS has been added
to all terminals through around 22Z-00Z this evening and TEMPOs
for KLAL and SWFL terminals where highest precipitation coverage
is expected to occur. This activity may result in brief IFR
restrictions but otherwise VFR conditions will prevail outside of
any convection. Rain chances will linger through around 02Z before
eventually tapering off overnight with mostly SE winds into
Sunday morning before the sea breeze allows winds to shift onshore
by Sunday afternoon.

&&

.MARINE...
Issued at 243 PM EDT Sat Jul 20 2024

Atlantic high pressure ridge axis is expected to remain in the
region with fairly typical summertime conditions through the
remainder of the weekend and into next week as afternoon into
evening seabreeze thunderstorms develop daily. Winds will
primarily be out of the southeast but will shift onshore each day
as the sea breeze develops with wind speeds generally expected to
be 10 kts or less. No headlines are expected but winds and seas
will be higher in the vicinity of any thunderstorm activity.

&&

.FIRE WEATHER...
Issued at 243 PM EDT Sat Jul 20 2024

Showers and thunderstorms are expected each day through the
remainder of the weekend and into next week as deep moisture
interacts with the sea breeze. However, no fire weather concerns
are expected as minimum relative humidity values remain well
above critical levels and wind speeds generally remain 10 mph or
less.

&&

.PRELIMINARY POINT TEMPS/POPS...
TPA  78  93  78  93 /  30  60  30  70
FMY  76  95  77  92 /  30  70  30  70
GIF  76  96  77  95 /  50  50  10  70
SRQ  77  95  77  93 /  40  60  30  70
BKV  73  95  74  95 /  30  70  30  70
SPG  82  94  82  93 /  30  50  40  70

&&

Sea Breeze Thunderstorm Regime For Sunday: 6
Sea Breeze Thunderstorm Regime For Monday: 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.

&&

DISCUSSION/AVIATION/MARINE/FIRE WEATHER...Giarratana
DECISION SUPPORT...Hubbard
UPPER AIR/CLIMATE...Hubbard