410
FXUS64 KBRO 182032
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
332 PM CDT Tue Jun 18 2024

...New SHORT TERM, LONG TERM, MARINE...

.SHORT TERM...
(Tonight through Wednesday night)
Issued at 329 PM CDT Tue Jun 18 2024

The short term forecast period will continue to focus on a
developing tropical cyclone over the Southwestern Gulf of Mexico
(over the Bay of Campeche). Deteriorating weather conditions are
expected to take shape through the short term period or through
Wednesday night. There are two main threats associated with this
system that we will talk about. One is the Heavy Rain and Flood
Threat. The other is the Winds and Marine/Beach Hazards or
threats.

Heavy Rain and Flood Threat:

The latest radar and satellite observations show isolated to
scattered showers over the region this afternoon. This activity
coincides with max sfc based differential heating in addition to the
continued influx of deep tropical moisture. As we progress through
tonight and into Wednesday, the risk/chance for rain and
thunderstorms will increase. The main uncertainty at this point is
where exactly the rain bands from this tropical system sets up.
Latest forecast models have become slightly more bullish on bringing
some of the heavier rain bands south through the day on
Wednesday. Showers and thunderstorms will come in waves given the
tropical nature of this event. The influx of moisture in the days
ahead will almost serve or act like an Atmospheric River (AR) from
the Gulf of Mexico into South/Southeast Texas. With precipitable
water (PWAT) values sampled between 2-2.5 inches, increasing on
the order of +3 to +4 STDEVs above normal, and the integrated
water vapor transport (IVT) values on the order of +1 to +3 STDEVs
above normal, rainfall rates are expected to be very efficient.
That said, flooding is expected especially across flood prone
areas (i.e. urban, poor drainage, low-lying areas). Hence, a Flood
Watch remains in effect for all of Deep South Texas and the Rio
Grande Valley from 1 AM CDT tonight to 1 PM CDT Thursday. Motorist
should place to leave early to their destinations, slow down, and
do not drive on any roads that become flooded.

While the rain threat associated with this tropical system could
become hazardous, it will also be very much beneficial for the
region. This coming rainfall will address the D0 (Abnormally Dry)
and D1 (Moderate Drought) over the region. Area dams and reservoirs
will also see improved water levels. Lastly, the year to date
deficit across our ASOS/Climate sites will flip from a deficit to a
surplus. Following this rain event, grasses are also expected to
greenup.

Winds and Marine/Beach Hazards:

The second threat/hazard aspect from this tropical system will be
the winds and marine/beach hazards. Winds from this tropical system
are expected to increase out of the northeast with gusts on
Wednesday ranging between 30-45 mph (highest near/along the coast).
Additionally, increased ocean swells have and will continue to
increase wave heights. Hence, we`ve updated the Coast Flood Watch
to a Coast Flood Warning. Additionally, we have a High Surf
Advisory and a High Risk for rip currents in effect.

&&

.LONG TERM...
(Thursday through next Tuesday)
Issued at 329 PM CDT Tue Jun 18 2024

Periods of showers and thunderstorms will persist through
Thursday and possibly into Friday before finally waning as the
aforementioned tropical system weakens and moves away. Reprieve
from the rain will be rather brief as forecast models and
ensembles are signaling another storm system tracking over the SW
Gulf of Mexico. This system similar to this first system could
bring another round over rain and thunderstorms to the region next
week. Will continue to monitor trends and provide more details in
the days ahead.

&&

.AVIATION...
(18Z TAFS)
Issued at 1251 PM CDT Tue Jun 18 2024

Through 18z Wednesday....

Aviation IDSS Key Messages:

* Isolated showers to become more numerous this afternoon; some
  embedded thunder is possible

* Rain/thunder threat increases tonight and continues through
  Wednesday

* IFR, possibly LIFR cigs/vsbys are possible under any
  thunderstorms that do develop

VFR conditions are taking place at all of the terminals under a FEW-
BKN deck of cumulus and stratocumulus clouds per the latest GOES-16
satellite imagery, with cloud bases between 3,000-6,000 feet AGL and
unrestricted visibilities.

The main concern during the 18z TAF cycle will be the increased
chances for showers and thunderstorms. According to the latest
radar, satellite and model observations, isolated showers and maybe
some embedded thunder are expected to become more scattered about
the area this afternoon as sfc daytime heating and influx of deep
tropical moisture from a developing tropical system to our south
increases. The main uncertainty is whether these showers make it
to any of the terminals this afternoon as they are very much hit
or miss given the isolated to scattered nature. Given the
situation, have VCSH in the TAFs for this afternoon into this
evening.

Through tonight and into Wednesday morning, showers and
thunderstorms are expected to become more numerous across the area
as the core of the tropical entity moves closer to land. However,
the main uncertainty is where exactly the rain bands set up. That
said, have Prob30 groups in the TAFs for now. Any showers or storms
that move over a terminal will have the capabilities of reducing
cigs/vis down to IFR and maybe even LIFR under the most intense
rainfall. Otherwise, expect for VFR conditions to prevail.

Winds will continue out of the east 15-25 kts with gusts as high as
35 kts or so through the TAF period. Winds will become strongest
towards the latter parts of the 18z TAF period in response to the
tropical system.

&&

.MARINE...
Issued at 329 PM CDT Tue Jun 18 2024

A tropical disturbance in the Southern Gulf of Mexico is expected to
move slowly northward then westward, making landfall in Mexico.
A large wind field extending to the north of this system will
support high seas as well as the potential for Tropical Storm Force
winds. A Tropical Storm Warning remains in place for the Laguna
Madre and Coastal Gulf waters. Winds and seas are expected to
improve over the weekend, with light to moderate winds and moderate
seas continuing through the remainder of the period.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             80  86  82  89 /  90 100 100 100
HARLINGEN               77  86  80  89 /  90 100 100 100
MCALLEN                 79  84  79  89 /  70 100 100 100
RIO GRANDE CITY         78  81  79  86 /  50 100 100  90
SOUTH PADRE ISLAND      81  86  84  86 /  90 100 100 100
BAYVIEW/PORT ISABEL     79  86  82  89 /  90 100 100 100

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Tropical Storm Warning for TXZ351-354-355-451-454-455.

     Flood Watch from 1 AM CDT Wednesday through Thursday afternoon
     for TXZ248>255-351-353>355-451-454-455.

     Coastal Flood Warning from 1 AM Wednesday to 1 PM CDT Thursday
     for TXZ351-354-355-451-454-455.

     High Rip Current Risk through Wednesday evening for TXZ451-454-
     455.

     High Surf Advisory until 7 PM CDT Wednesday for TXZ451-454-455.

GM...Tropical Storm Warning for GMZ130-132-135-150-155-170-175.

&&

$$

SHORT TERM...23-Evbuoma
LONG TERM....23-Evbuoma
AVIATION...23-Evbuoma