899
FXUS64 KBRO 271943
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
243 PM CDT Mon May 27 2024

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

.SHORT TERM...
(Tonight through Tuesday night)
Issued at 242 PM CDT Mon May 27 2024

Key Messages:

* Marginal Severe Weather Risk western portions this evening
* Elevated heat index values will be back Tuesday afternoon

Western sections of the CWA are in a marginal risk of severe weather
outlook through tonight. The eastern half of the CWA is in a general
thunderstorm outlook. Some convection has developed to the west over
the Sierra Madre Oriental Range and may drift towards the Rio Grande
Plains and Upper/Mid Valley with the flow aloft this afternoon as a
weak, destabilizing short wave trough moves through the extant H5
ridge. Models depict ample CAPE and moderately steep lapse rates to
the west, so if any deeper cells develop and can maintain integrity,
there could be a large hail and damaging wind threat. These cells
will likely remain unorganized and isolated in nature, however. For
Tuesday night, the CWA is in a general tstorm outlook supporting a
slightly diminished threat.

Overnight temps will remain warm, in the upper 70s to lower 80s,
with heat index values ranging from the upper 70s across the
Ranchlands to the lower 90s for the Lower RGV. As the erstwhile mid-
level ridge erodes to the north and its center slips subtly to the
west in the short term, the heat will ease up a bit. For Tuesday,
most inland temperatures will still hit or exceed the century mark,
supporting heat index readings above heat advisory criteria (111 to
115 degrees) for a few hours. Low temperatures Tuesday night may
drop a degree or so, but heat index values will still mirror those
of tonight, ranging from the upper 70s to the lower 90s, or at least
in that neighborhood by dawn`s first light.

Since winds have relaxed a bit, wave heights are also decreasing and
the rip current risk will likely drop to moderate on Tuesday.

&&

.LONG TERM...
(Wednesday through next Monday)
Issued at 242 PM CDT Mon May 27 2024

Key Messages:

*Above normal high and low temperatures
*Very little rain chances

The mid-level ridge continues to be the dominant feature for the long
term forecast period even though it does move a bit to the south-
southwest by Thursday. This will allow for the heat to continue to
be the biggest talking point in this forecast discussion. The high
temperatures for the long term forecast period are expected to be in
the range of upper 90s along the coast and the barrier island, to
the triple digits for the rest of Deep South Texas and the Rio
Grande Valley. However, with the onshore flow at the surface
bringing in plenty of humidity to the region, the temperatures will
feel hotter than that. With heat indices in the range of 105-114
each day. However, some days within the long term forecast period
are rather questionable on if a Heat Advisory is needed or not.
While the heat indices will be meeting that criteria, it is a
question of if the heat indices will be that high for an extended
period of time or if there will be enough spatial coverage for it as
well. As of the latest model guidance, Friday and Saturday look to
be the mostly likely for needing a Heat Advisory the inland portions
of the area. On the other hand, the rest of the long term forecast
period indicates that a Special Weather Statement about the heat
indices might be enough. Further shifts will have to continue to
monitor this developing situation and see how the models continue to
trend.

To add on to this situation, the overnight low temperatures are also
expected to be above normal as well. Nightly low temperatures are
expected to be in the range of upper 70s to low 80s. At the same
time, the humidity at night will result in heat indices at night
being in the range of upper 70s in the Northern Ranchlands, to upper
80s in the Lower Rio Grande Valley.

By Friday, the pressure gradient over the region is expected to
strengthen as a thermal low pressure over Mexico interacts with a
building high pressure over northeast Mexico, which could result in
a Wind Advisory for Cameron, Willacy, and Kenedy counties on that
day.

Finally, the rain chances for the long term forecast are still quite
low, but they are not zero. It is possible that some convection
could fire up along the Sierra Madre and then move into the Northern
Ranchlands. However, any showers or thunderstorms that do so will be
moving into an unfavorable environment as the middle and upper
levels of the atmosphere are still dry aloft and stable thanks to
the mid-level ridge.

&&

.AVIATION...
(18Z TAFS)
Issued at 1207 PM CDT Mon May 27 2024

MVFR conditions at the TAF sites now due to ceilings, but pesky
haze is also slightly limiting visibility. There is a large CU
field covering an area inclusive of the TAF sites, as well as a
weak sea breeze developing along the coast. Southeast winds are
light to moderate, slightly weaker than previous days. Ceilings
will develop and descend to MVFR this evening, as they have in
recent evenings. Fog/haze will again set up late tonight through
late Tuesday morning or early afternoon, with slight visibility
restriction. Though a few showers/thunderstorms will be possible
tonight to the west, the confidence in storms approaching the TAF
sites still appears low, though some guidance does still mention
it.

&&

.MARINE...
Issued at 242 PM CDT Mon May 27 2024

Now through Tuesday night...With slightly weaker winds compared
to previously, moderate southeast breezes and moderate wave
heights will prevail in the short term. High pressure across the
Gulf will provide the driving force for the seasonal winds.

Wednesday through Next Monday...Moderate southeasterly winds and
moderate seas are likely through next Monday. 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  for a majority of the day. Small Craft Advisories
become more likely by Friday and last through the rest of the
period.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             81  95  81  95 /  10  10  10  10
HARLINGEN               78  99  78  98 /  20  10  10  10
MCALLEN                 81 101  80 100 /  20  10  10  10
RIO GRANDE CITY         80 101  78 101 /  40  10  20  10
SOUTH PADRE ISLAND      82  86  82  87 /  10  10  10  10
BAYVIEW/PORT ISABEL     80  92  80  93 /  10  10  10  10

&&

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

     Heat Advisory until 8 PM CDT this evening for TXZ351-354-355.

     High Rip Current Risk until 7 PM CDT this evening for TXZ451-454-
     455.

GM...None.
&&

$$

SHORT TERM...54-BHM
LONG TERM....64-Katz
AVIATION...54-BHM