942
FXUS64 KBRO 182327
AFDBRO

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

...New AVIATION...

.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...
(00Z TAFS)
Issued at 626 PM CDT Tue Jun 18 2024

Through 00z Thursday....

Aviation Weather Key Messages:

* Scattered to numerous showers and storms taper down this evening

* Rain/thunder threat increases again tonight and continues through
  Wednesday

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

VFR-MVFR conditions were taking place at the terminals this evening
with scattered to numerous rain showers over the region, per the
latest scans of the Doppler Radar.

After this first wave moves through, things should taper down with
VFR-MVFR conditions continuing through the rest of this evening.
Tonight, rain/thunder chances and coverage are expected to increase
with things peaking between the overnight hours into the afternoon
hours on Wednesday. During this time, there will be waves of showers
and storms occurring, with some capable of producing very heavy
rainfall. Any storms that do move over any of the terminals will
have the capabilities of reducing cigs/vis down to IFR or maybe even
LIFR levels. Things will gradually taper down Wednesday evening and
beyond the 00z period.

East-northeast winds 15-22 kts with gusts between 30-35 kts are
expected through the 00z TAF cycle.

&&

.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