Severe Thunderstorm Warning 29, NWS Brownsville, TX

Area Forecast Discussion
National Weather Service Brownsville TX
320 PM CDT Mon May 13 2024

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

.SHORT TERM...
(Tonight through Tuesday night)
Issued at 315 PM CDT Mon May 13 2024

Key Messages:

-Hot temperatures today with a Heat Advisory until 7 PM.

-Strong to severe storms will be possible later tonight.

First up, let's talk heat. Southerly flow and 850mb temperatures of
23C-25C will allow for temperatures this afternoon to reach mid 90s.
The hot temperatures combined with high humidity will make "feels
like" reach the triple digits. We currently have a Heat Advisory out
until 7 PM CDT for inland Kenedy, inland Willacy, inland Cameron and
Hidalgo counties. Heat indices could reach 114 degrees. A weak cold
front will move through Deep South Texas on Tuesday which will help
keep temperatures a few degrees cooler. With that said, its still
going to be hot with highs in the 90s for most of the region.
Humidity levels will not be quite as high, so while heat indices are
still expected to reach the triple digits (mainly along the river)
we are not looking at Heat Advisory conditions for Tuesday.

Now, let's talk rain and thunderstorms. We had a round of scattered
rain showers and thunderstorms this morning which have all moved out
of the area. As we head into later this afternoon into this evening
we could get another round of thunderstorms. This activity has the
potential to be more robust, thanks to building instability through
this afternoon. CAMs models are beginning to come into better
agreement with a line of thunderstorms over the CRP CWA and moving
southeast through the afternoon and begin to push into the northern
Ranchlands as early as 22z. These storms will continue to move
southeast through the evening. Some of this activity may be strong
to severe. Main threats will be large hail, with CAPE values across
the CWA exceeding 3000 J/kg and lapse rates around 7.5C, and high
wind gusts in excess of 60 mph. Brief heavy rainfall and frequent
cloud to ground lighting will also be possible with this activity.
The SPC has portions of Kenedy, Brooks and Jim Hogg counties in a
SLIGHT risk for severe weather (2 out 5) and the remainder of the
CWA in a MARGINAL risk (1 out of 5) of severe weather. This activity
should move out of the region by around midnight.

&&

.LONG TERM...
(Wednesday through next Monday)
Issued at 315 PM CDT Mon May 13 2024

The upper-level flow over South Texas looks to be generally south
westerly for the start of the long term period. An upper level
trough looks to move through the region Friday and Saturday,
making way for an upper-level ridge to build into the area near
the end of the period. A couple of shortwaves moving through the
upper-level flow could enhance forcing over Deep South Texas
Wednesday, Thursday, and Friday Afternoons.

At the surface, easterly winds are expected to shift
southeasterly Wednesday, transporting additional moisture and
warmer air to the region. A surface low looks to develop over
North Texas on Friday, with a cold front stretching southwesterly
across Central Texas. This cold front is expected to drop
southeast through the day Friday, possibly reaching Deep South
Texas Friday afternoon. This cold front looks to be fairly weak by
the time it reaches Deep South Texas, and will likely only reduce
temperatures a couple of degrees.

Winds look to briefly shift northeasterly behind the front Friday
evening, before shifting back to the southeast by Saturday
afternoon, allowing warmer air and additional moisture to mover
into the area through the remainder of the period.

Rain chances through the period have trended downwards with the
latest guidance runs. The best chance for rain looks to be Friday,
ahead of the cold front, but that is only about a 10-20% chance.

The primary threat looks to be heat, with heat index values
forecast to reach 111-115 Thursday and Friday afternoons for the
eastern two thirds of the CWA. Heat Advisories will likely be
needed both days. Additional heat advisories may be needed for the
eastern counties Saturday and Sunday, though conditions look to
be more borderline.

&&

.AVIATION...
(18Z TAFS)
Issued at 1220 PM CDT Mon May 13 2024

VFR conditions will prevail at HRL and MFE this afternoon with
MVFR at BRO. Later this evening we are expecting a line of showers
and thunderstorms to move through the region. The best timing for
this activity will be between 00z and 06z. At this time MVFR and
potentially brief periods of IFR are possible at MFE, HRL and BRO.
Along with the lowered visibilities the strongest storms will be
capable of wind gusts in excess of 40kts, and 1 inch or greater
hail. Activity will move out overnight with MVFR ceiling
prevailing overnight.

&&

.MARINE...
Issued at 315 PM CDT Mon May 13 2024

Tonight through Tuesday night..Generally favorable conditions
are expected on the waters off the lower Texas coast through much of
the forecast. The caveat will be later this afternoon into tonight
as a line of strong to possibly severe thunderstorms moves moves
southeast. This activity could produce large hail and strong winds
will lead to localized hazardous marine conditions. The best timing
for the potential for severe weather will be from 22z to 00z.
Showers and storms exit the region by daybreak with a cold front
moving southward through the day on Tuesday.

Wednesday through next Monday...High pressure across the Gulf will
generally keep winds and seas light to moderate through the
period. The exception looks to be Wednesday and Thursday
afternoons, where an upper-level shortwave looks to enhance
surface low pressure over northern Mexico, strengthening pressure
gradients along the coast, and briefly increasing wind speeds.
Small Craft Should Exercise Caution headlines will likely be
needed both afternoons.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             78  92  76  91 /  20  10   0  10
HARLINGEN               75  92  73  93 /  20  10   0  10
MCALLEN                 77  96  76  95 /  20  10   0  10
RIO GRANDE CITY         75  97  74  96 /  10  10   0  10
SOUTH PADRE ISLAND      79  84  78  84 /  20  10   0   0
BAYVIEW/PORT ISABEL     77  87  75  89 /  20  10   0   0

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Heat Advisory until 7 PM CDT this evening for TXZ251-253>255-353.

GM...None.
&&

SHORT TERM...68-McGinnis
LONG TERM....60-BE
AVIATION...68

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