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FXUS64 KBRO 230548 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1248 AM CDT Mon Sep 23 2024

...New AVIATION...

.SHORT TERM...
(Tonight through Monday night)
Issued at 214 PM CDT Sun Sep 22 2024

Mid-level ridge continues to a major player in the short term
forecast for Deep South Texas and the Rio Grande Valley through
the short term forecast period. As the ridge will start to drift
off towards the east more by Monday, a weak mid-level trough will
start to move into the eastern part of Texas. With daytime heating
and a small increase in PWAT values, there is a slightly greater
chance for isolated showers and thunderstorms to occur over the
eastern most counties along with the sea breeze during the
afternoon tomorrow.

As for the temperatures, highs are expect to be generally in the
low to mid 90s. The heat indices are expected to be around 105,
which is below the criteria for a Special Weather Statement for
elevated heat indices and Heat Advisory. The low temperatures are
expected to be in the 70s.

&&

.LONG TERM...
(Tuesday through next Sunday)
Issued at 214 PM CDT Sun Sep 22 2024

Deep mid-level troughing over the North Central Plains, the right
(east) side of an omega block over the Western CONUS, will stand
in counterpoint to modest, east to west elongated ridging over the
Gulf and South Texas at the beginning of the long term (Tue). A
tropical system will concurrently be taking shape over the NW
Caribbean (see the marine discussion below for more detail).

Deep South Texas and the Gulf of Mexico will see mainly seasonal
but nonetheless somewhat unsettled weather during the initial
phase of the long term. Convection over the Gulf of Mexico will be
a staple, but daytime sea breezes will feed off ample available
moisture and will spread over the CWA with isolated to scattered
showers and tstorms Tuesday through Wednesday and early Thursday.
Efficient precipitation processes may result at times in brief
heavy rainfall, with the threat of mainly isolated, nuisance type
flooding. We forecast modest accumulation below flash flood
guidance through Thursday.

The mid-level low will drop south into the Southern High Plains
by Wednesday and Thursday, pulling drier air across West Texas
toward the lower RGV behind a cool front. The front may be strong
enough to push through the CWA to the Gulf Thursday afternoon, all
but ending any significant rain chances for the remainder of the
long term. Meanwhile, the mid-level low itself and the northward
moving tropical system appear to do a dance with each other Friday
and Saturday, interacting and somehow combining over the lower to
mid Mississippi Valley. That scenario leaves deep South Texas
more or less out of the main action and takes us to the end of the
current long term.

Through the early long term, temperatures will trend slightly above
normal with a good mix of clouds and sun and light to moderate
winds. High temps will be mainly in the lower to mid 90s with lows
in the lower to mid 70s. By Wednesday (the best day for rain) east
to southeast winds will start to back to north and northeast as they
will be influenced by low pressure to the north instead of Gulf high
pressure. Some drying will occur on Thursday, followed by fewer
clouds next Friday through Sunday as the drying continues. Overnight
low temps starting Thursday night will trend down slightly - toward
more normal values due to the drier air. Rip current risk may
increase mid to late week as larger, longer period swells make their
way west across the Gulf toward the lower Texas coast.

&&

.AVIATION...
-- Changed Discussion --
(06Z TAFS)
Issued at 1249 AM CDT Mon Sep 23 2024

Another quiet weather day is on tap for landings/takeoffs for
this Monday...with perhaps a slight uptick in the potential for
isolated early afternoon showers or even a rogue thunderstorm as
mid level moisture gets a slight boost across the lower Valley.
Confidence is low at this point as dry air is pretty stout above
the usual cumulus/stratocumulus deck at the lifting condensation
level which rises from high MVFR through low VFR. Across the
mid/upper Valley (McAllen/Miller area) the very dry air layer
holds through at least 4 PM. For now...have left Brownsville out
of mentionable rain but included a VCSH for Harlingen as the sea
breeze may coincide with the slight uptick in moisture.

As for clouds...heating/moisture percolation should pop the usual
cumulus by 9 or 10 AM in the lower Valley and a little later for
McAllen. Added periodic broken conditions based on Sunday`s
observations but mostly in low VFR conditions. Should see some
isolated congestus but that`s about it. By late afternoon in the
lower Valley and just after sunset in McAllen, skies should clear
once again.

As for winds...guidance a touch low following the afternoon sea
breeze enhancement and based on Sunday have nudged speeds up a few
knots before laying down to light by or just after sunset.
-- End Changed Discussion --

&&

.MARINE...
Issued at 214 PM CDT Sun Sep 22 2024

Tonight through Monday Night...Favorable marine conditions are
expected to persist through Monday night. Light to moderate
onshore flow and low to moderate seas will continue through the
period. Isolated showers and thunderstorms are possible and could
result in locally elevated winds and seas.

Tuesday through Friday night...we expect light to moderate east
to southeast winds and low to moderate seas through Tuesday night.
East to southeast winds will back to north and northeast on
Wednesday and will subsequently become moderate to fresh over the
Gulf of Mexico waters on Thursday. Small craft should exercise
caution to low end small craft advisory conditions will be
possible on Thursday through Friday night on the Gulf, mainly from
building seas. Isolated to scattered showers and thunderstorms
will develop from time to time through Thursday or Thursday night.

A broad area of low pressure is over the NW Caribbean Sea and
adjacent parts of Central America. Environmental conditions appear
favorable for gradual development of this system during the next
several days. A tropical depression will likely form while the
system moves slowly north across the northwestern Caribbean Sea
and Gulf of Mexico through the end of the week. There is a high
chance (80%) of tropical cyclone formation in the next seven days.
Regardless of development, winds and seas will start increasing
across the SE Gulf early this week.

&&

.PRELIMINARY POINT TEMPS/POPS...
-- Changed Discussion --
BROWNSVILLE             77  90  76  91 /  30  60  20  60
HARLINGEN               74  92  74  91 /  10  60  10  60
MCALLEN                 77  96  77  94 /  10  40  20  50
RIO GRANDE CITY         74  94  75  93 /  10  30  20  50
SOUTH PADRE ISLAND      80  87  81  87 /  40  50  30  50
BAYVIEW/PORT ISABEL     77  89  76  88 /  20  50  20  50
-- End Changed Discussion --

&&

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

$$


AVIATION Update...52-Goldsmith