558
FXUS64 KBRO 281956
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
256 PM CDT Tue May 28 2024

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

.SHORT TERM...
(Tonight through Wednesday night)
Issued at 255 PM CDT Tue May 28 2024

Key Messages:

- Heat Advisory in effect through 8 PM.

- Slight risk (level 2 of 5) for severe thunderstorms late this
evening and tonight.

The influence of the mid/upper level ridge will still be present
through the short term period, but won`t be quite as strong as it
was over the weekend. This will place Deep South Texas in a more
favorable region for unsettled weather (as we saw with last night`s
storms) through tomorrow as a shortwave tracks over South Texas. The
latest radar and satellite imagery depict partly to mostly sunny
skies and rain-free conditions across all of Deep South Texas this
afternoon. Meanwhile, an MCS continues to track into Southeast Texas
after barreling across North Texas early this morning, sending an
outflow boundary toward South Texas. A few showers and thunderstorms
have developed off of the boundary, but there should be an uptick in
coverage as the boundary translates south and encounters a favorable
environment for convective initiation. In the meantime, hot and
humid conditions will persist across Deep South Texas, with heat
indices approaching 111-115 degrees through the early evening hours.

In addition to monitoring any convective development along/ahead of
the aforementioned outflow boundary, we`ll also need to keep an eye
on convection developing along the Sierra Madre late this afternoon
into the early evening hours. Well established low level southerly
flow has maintained high precipitable water values across the
region, with BRO`s 12Z sounding observing a PWAT of 1.75 inches.
Similarly, high res guidance maintains similar or slightly higher
values tonight into tomorrow. Forecast model soundings indicate the
presence of 7-8 C/km mid level lapse rates, MUCAPE values around
2000-3500 J/kg, and bulk shear values around 30-40 knots. All in
all, a favorable environment that would support the development of
severe thunderstorms with a threat for large hail and damaging winds
late this evening and overnight. Initial thoughts are that any
convection will reach the Rio Grande Plains after 9-11PM, and track
further east toward the I-69 corridor closer to 2-4AM.

There is still some uncertainty on the development of any severe
thunderstorms tonight, mainly across areas closer to the coast as
the environment is slightly less favorable. This will result in a
weakening trend as the convection tracks closer to the Gulf waters.
Most of the high res guidance is favoring a solution with convection
developing off of the Sierra Madre rather than any convection along
the outflow boundary, but it is still something to keep an eye on in
the evening hours.

Low precipitation chances (around 20%) will exist on Wednesday as
the shortwave continues to track toward the Mid Texas Coast.
Otherwise, another warm day with highs in the upper 90s to around
100 degrees with heat indices ranging from around 105 to 114 degrees
during the afternoon hours. A Heat Advisory may be needed for
portions of the region, but the potential for isolated to scattered
showers and thunderstorms may keep temperatures lower than forecast.
Otherwise, low in the mid 70s to low 80s are expected tonight and
Wednesday night.

&&

.LONG TERM...
(Thursday through next Tuesday)
Issued at 255 PM CDT Tue May 28 2024

Key Messages:

-Above normal high and low temperatures

-Very little rain chances

The mid-level ridge continues to be the driving force for the
weather for Deep South Texas and the Rio Grande Valley. While the
center of the ridge will shift between south of the Baja Peninsula to
Central Mexico. This pattern will put the region into a hot and
mostly rain free pattern. Temperatures are expected to be above
normal with Heat Advisories being needed for almost every day during
the long term forecast period. While the heat indices are expected
to be in the range of 105 to 114 through the long term forecast
period. Friday seems to be a very borderline day on if a Heat
Advisory will be needed. Will need to further shifts to continue to
monitor how the models handle the heat indices leading up to Friday.
Otherwise, Heat Advisories are likely for the inland counties within
the CWA.

As for the rain chances, while some convection is likely to develop
along the Sierra Madre, the questions remains on if those showers
and thunderstorms will be able to make into Deep South Texas and the
Rio Grande Valley. Models continue to show that the middle and upper
levels of the atmosphere are expected to be dry. Along with the mid-
level ridge, the atmosphere does not appear to be very favorable for
showers and thunderstorms. However, cannot rule out a rouge isolated
shower or thunderstorm making its way into the region.

Finally, an enhanced pressure gradient will see the surface winds
pick up over the region that could result in a Wind Advisory for
Cameron, Willacy, and Kenedy counties possibly Saturday through
Monday.


&&

.AVIATION...
(18Z TAFS)
Issued at 1246 PM CDT Tue May 28 2024

Satellite imagery and observations depicts SCT to BKN VFR
ceilings this afternoon across the region. MVFR ceilings will
develop once again after 01-02Z at BRO and HRL, and closer to 04Z
at MFE. Convection is expected to develop late this evening near
the Sierra Madre Mountains and track east toward the terminals
after 06-0Z at MFE and closer to 09-11Z at HRL and BRO. There is
still some uncertainty in the development of any thunderstorms and
whether they reach as far east as HRL and BRO. With this TAF
issuance, opted to add in VCTS For MFE from 07-11Z, but leave HRL
and BRO precip-free. Adjustments to timing at MFE and inclusion
of VCTS/TSRA at HRL and BRO will need to be monitored closely.

&&

.MARINE...
Issued at 255 PM CDT Tue May 28 2024

Now through Wednesday night...Generally favorable marine
conditions are expected as light to moderate southeast winds and
low to moderate seas prevail. There may be a brief period of Small
Craft Exercise Caution conditions Wednesday afternoon, mainly
along the Laguna Madre, due to occasional higher wind gusts. Low
rain chances will exist tonight and tomorrow.

Thursday through Next Tuesday...Moderate southeasterly winds and
moderate seas are likely through next Tuesday. With a thermal low
over Mexico and high pressure over the Gulf of Mexico, the pressure
gradient is going to be enhanced, which will result in Small Craft
Exercise Caution. Small Craft Advisories become more likely by
Friday and last through the rest of the period.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             80  96  81  95 /  20  20  10  10
HARLINGEN               78  97  79  98 /  30  20  10  10
MCALLEN                 79 100  80 100 /  30  20  10  10
RIO GRANDE CITY         78 100  79 101 /  40  20  20  10
SOUTH PADRE ISLAND      81  87  82  87 /  20  20  10  10
BAYVIEW/PORT ISABEL     80  93  80  93 /  20  20  10  10

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Heat Advisory until 8 PM CDT this evening for TXZ248>255-351-
     353>355.

GM...None.
&&

$$

SHORT TERM...22-Garcia
LONG TERM....64-Katz
AVIATION...22-Garcia