009
FXUS64 KBRO 241748 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1248 PM CDT Tue Sep 24 2024

...New AVIATION...

.SHORT TERM...
(Today through Wednesday)
Issued at 346 AM CDT Tue Sep 24 2024

An elongated mid-level ridge is expected to remain in place over
Deep South Texas and the Rio Grande Valley today. A 500mb trough/low
will dig southward into the Middle Mississippi River Valley on
Wednesday and push the associated cold front into south Texas. In
addition, Potential Tropical Cyclone Nine should strengthen to a
tropical depression or storm as it enters the eastern Gulf of
Mexico.

Above normal temperatures will continue through the short term.
Highs today and Wednesday are expected to be in the low to mid 90s,
except for the 80s along the coast. Heat indices should range
between 100 to 107. This is still below the criteria for a Special
Weather Statement for elevated heat indices and Heat Advisory. The
low temperatures for tonight will fall into the 70s, except around
80 for the beaches.

Lastly, while the rip current risk is low today through Wednesday.
Wave run up along the beaches could reduce the available beach space
down. While not expecting to need Coastal Flood Advisory at this
point. A Coastal Flood Statement may be needed around high tide,
which is at 2:03 AM Wednesday.

&&

.LONG TERM...
(Wednesday night through Monday)
Issued at 346 AM CDT Tue Sep 24 2024

By Wednesday night, the NHC forecasts PTC 9 to have strengthened
to a hurricane and entered the Eastern Gulf. As the tropical
system approaches Florida, it will interact with an upper-level
closed low over the Southeastern US. This interaction will shift
the closed low to the southwest, into the ArkLaTex region. At the
surface, a cold front associated with this system will drop south,
moving through the CWA Wednesday night into Thursday morning.
PWAT values between 1.5 and 2 inches and CAPE values around 1000
J/kg ahead of the front could support some isolated to scattered
showers and thunderstorms Wednesday night and early Thursday
morning.

Behind the front, a drier airmass and northwesterly flow to
westerly flow aloft will keep rain chances near zero through the
remainder of the period. High temperatures behind the front arent
expected to change much. The highs will be slightly lower
Thursday afternoon, topping out in the upper 80s to low 90s, then
quickly returning to the low to mid 90s over the weekend. Low
temperatures will fall into the mid to upper 60s Thursday night,
then gradually return to the low to mid 70s over the weekend.

The combination of the frontal passage and the arrival of long
period swell from the tropical system in the Eastern Gulf will
result in increased wave heights and adverse beach conditions
Thursday and Friday. Enhanced rip current risk and minor coastal
flooding will be possible at beaches along the Lower Texas Coast.

&&

.AVIATION...
(18Z TAFS)
Issued at 1248 PM CDT Tue Sep 24 2024

Scattered showers have prevailed across the Lower Texas Gulf
waters, but the typical "jump" along the sea breeze has been slow
to go. Convective-allowing models as well as global models have
been rather bearish for this afternoon...and with limited forcing
underneath the upper level ridge this makes sense. So...given low
confidence have elected to roll a VCSH for all terminals until the
sea breeze passes and stabilizes things. This would be around 2-3
PM in Brownsville and by 4 PM in Harlingen. Added to McAllen as
well and maintained through sunset.

Otherwise...light winds becoming east around 10 knots post-sea
breeze this afternoon before laying to to near calm by mid
evening, with skies clearing except for few-scattered MVFR
cumulus near Brownsville.

As for Wednesday...incoming models are also more bearish on rain
chances even though energy arrives from the north via an upper-
level trough dipping into the lower/mid Mississippi Valley with
associated shear axis running from Louisiana through south Texas
by midday. This, combined with any early morning showers sneaking
onshore, may be enough to trigger isolated activity for
Brownsville/Harlngen after 9 or 10 AM. For now, called it VCSH
with periodic MVFR ceilings through 1 PM., with McAllen scattered
for now.

&&

.MARINE...
Issued at 346 AM CDT Tue Sep 24 2024

Today through Wednesday...Favorable conditions are expected to
prevail along the Lower Texas Coast through the period. A weak
pressure gradient will support light to moderate onshore flow and
low to moderate seas. Isolated showers and thunderstorms are
possible through the period and could result in locally elevated
winds and seas.

Wednesday night through Monday...The NHC forecasts PTC 9 to
strengthen to a hurricane as it enters the Eastern Gulf by
Wednesday night. Swell from this system will likely arrive
Thursday, and combined with the passage of a cold front Wednesday
night, this will lead to enhanced seas. Small Craft Should
Exercise Caution headlines or Small Craft Advisories may be needed
for the Gulf waters Thursday and Friday as wave heights look to
reach 6-7 feet. Seas are expected to subside over the weekend,
with favorable marine conditions prevailing through the remainder
of the period.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             91  77  91  74 /  40  20  40  20
HARLINGEN               91  74  91  72 /  40  10  40  10
MCALLEN                 95  78  95  74 /  30  10  30  20
RIO GRANDE CITY         94  76  94  73 /  20  10  30  20
SOUTH PADRE ISLAND      88  81  87  79 /  40  20  40  30
BAYVIEW/PORT ISABEL     89  76  89  74 /  40  40  30  20

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$


AVIATION Update...52-Goldsmith