Special Weather Statement, NWS Brownsville, TX

Area Forecast Discussion
National Weather Service Brownsville TX
1225 AM CDT Tue May 19 2026

...New AVIATION...

.KEY MESSAGES...
Updated at 1217 AM CDT Tue May 19 2026

Key Messages:

* Day-to-day or near day-to-day chances for showers and
  thunderstorms is expected through next weekend and possibly beyond
  amid a major shift in the weather pattern.

* Strong to severe thunderstorms along with heavy rainfall and
  localized flooding is possible through next weekend.

* Hot and humid conditions will take place once again on Tuesday;
  maximum heat indices between 105-111F degrees will result in
  widespread Major (Level 3 of 4) Heat Risk.

* A Small Craft Advisory remains in effect till 9 AM CDT Tuesday; a
  High Risk for Rip Currents is also in effect through at least
  Tuesday evening.

&&

.DISCUSSION...
Issued at 1106 PM CDT Mon May 18 2026

Hot temperatures featuring Moderate (Level 2 of 4) to Major (Level 3
of 4) Heat Risk through Tuesday (possibly into Wednesday), and an
increasingly unsettled weather pattern punctuating a significant
pattern change from dry to wet remains to be the two main weather
headlines through the forecast period.

...ACTIVE/WET WEATHER DEVELOPS THIS WEEK; MULTIPLE ROUNDS OF STRONG
TO SEVERE THUNDERSTORMS AND HEAVY RAINFALL IS POSSIBLE...

Global computer and AI/ML models/ensembles continue to advertise a
significant pattern change from dry to wet beginning this week. A
split-flow 500 mb pattern featuring what will become an increasingly
active and persistent southwest flow aloft sub-tropical jet or
southern branch jet stream is in place. This will serve as a conduit
for multiple impulses/perturbations tracking over the region over
the next several days. Later in the week through next weekend, there
are signs that mid-upper troughing along with multiple
impulses/perturbations will undercut high pressure/ridging aloft.

Closer to the sfc, a frontal boundary will sag southward across the
U.S. before stalling and meandering to our north across the southern
Plains. A better than normal jet structure will be in place through
this week. Additionally, southerly flow near the sfc will yield a
pool of deep tropical moisture helping to increase the atmospheric
water content over the region through the week ahead. This is
justified with sample maximum precipitable water (PWAT) values
between 1.80-2.50 inches, some 1-3 STDEVs above normal and above the
90th percentile of sounding climatology for mid to late May.
Furthermore, high instability values will be present through this
week with steep mid level lapse rates between 6.5-8.0 C/km, SBCAPE
values between 2,000-4,000 J/kg, MLCAPE values between 1,000- 2,000
J/kg, a moderately to very unstable atmosphere with Showalter values
ranging between -2 and -6.

All in all, the combination of a favorable mid-upper level 500 mb
steering pattern, favorable jet stream dynamics, high atmospheric
moisture content, and high instability will support a noticeable
change to a wetter/active weather pattern this week and possibly
beyond. This includes incessant day-to-day or near day-to-day
chances for showers and thunderstorms through this week, and maybe
through the remainder of May. The best chances for rain this week
will be later in the week into next weekend. Strong to severe
thunderstorms are possible given the atmospheric and forcing
ingredients highlighted above. The Storm Prediction Center (SPC)
continues to have the northwestern half of our area under a
Marginal Risk (Level 1 of 5) for severe thunderstorms on Tuesday.
This includes all of Zapata and Jim Hogg Counties, and most of
Brooks and Starr Counties in it's latest SWODY2.

Given the high atmospheric moisture content available, heavy
rainfall and instances of flooding is possible through the week,
especially later in the week. This is especially true for slow
moving thunderstorms that repeatedly track over the same areas. The
Weather Prediction Center (WPC) continues to have the entire
forecast area or all of Deep South Texas under a Marginal Risk
(Level 1 of 4) for Excessive Rainfall in it's Day 4 (Thursday) and
Day 5 (Friday) ERO.

Through tonight, a thundershower or two is possible. Latest radar
scans reveal a blossoming thunderstorm moving northeast off the
slopes of the Sierra Madre with batches of showers further to the
north and west. Will have to monitor trends through tonight. For
now, we have low (20%) chance PoPs across much of the area. Should
the thunderstorm to our southwest off the Sierra madre hold
together, we may need to bump PoPs later tonight. For Tuesday night
into Wednesday morning, several hi-res CAM guidances continue to
advertise a squall line of strong to severe thunderstorms or MCS
originating from central Texas and advancing southward through Deep
South Texas late Tuesday into Wednesday between midnight and 9 AM
Wednesday morning. Currently, we have low-medium (20-50%) chances
for showers and thunderstorms across the region late Tuesday night
into Wednesday morning. This may need bumping up depending on things
evolve. Again the Storm Prediction Center (SPC) has a Marginal Risk
for severe thunderstorms Tuesday night into Wednesday, currently
favoring Zapata, Jim Hogg, Starr, and Brooks Counties.

Wednesday night through the early parts of next week, additional
precipitation chances exists. During this timeframe, we could see
another one or two squall lines or MCSs with a heavy rainfall threat
move through Deep South Texas and the Rio Grande Valley. Wednesday
night-Thursday night, we have 30-70% chances for showers and
thunderstorms over the region. Friday night through Saturday night,
we have widespread categorical chances ranging between 50-75%.
Sunday through Monday, there's a 40-60% chance for showers and
thunderstorms across the region. Finally, Monday night through
Tuesday night, there will be low chances ranging between 20-30%.

Through Saturday, quantitative precipitation forecasts (QPF) or
rainfall amounts are expected to range between 1-2 inches with
locally higher amounts across Deep South Texas and the Rio Grande
Valley. The rain to come will certainly prove to be beneficial,
helping to further improve the D1 (Moderate) to D2 (Severe) Drought
status across the region.

...ANOTHER HOT DAY EXPECTED ON TUESDAY WITH WIDESPREAD MAJOR HEAT
RISK...

The other weather headline through Tuesday will be the heat! Global
forecast models/ensembles continue to depict a sharp 588-591 dam sub-
tropical heat ridge over the region. This feature will result in
another day of hotter than normal temperatures on Tuesday, and maybe
even extending into Wednesday. Similar to today, forecast high
temperatures for Tuesday are expected to be in the mid 90s to lower
100s with the hottest temps west of IH-69C/US-281. Dewpoints in the
mid 70s will result in max heat indices or apparent temperature
values climbing to between 105-111F degrees on Tuesday. These values
will once again yield Moderate (Level 2 of 4) to Major (Level 3 of
4) Heat Risk. Cloud over will be a factor in these temperatures
being realized.

By Wednesday, the aforementioned heat ridge relaxes which should
result in a slightly cooler day. Shower and thunderstorm chances
Tuesday night into Wednesday as well as cloud cover could also play
a role in the slightly lower temperatures from Monday and Tuesday.
Nonetheless, it will be another warmer than normal day with high
temperatures in the low to mid 90s. With heat indices ranging
between 100-108F degrees, Heat Risk scores will be mainly fall in
the Moderate (Level 2 of 4) category over the region on Wednesday.

Thursday through next Tuesday, high temperatures will range between
the upper 80s to lower 90s. This largely will be attributed to the
shower and thunderstorm chances during this timeframe. Tonight
through Tuesday night, overnight lows are progged to be in the upper
70s to lower 80s. Wednesday night through next Sunday night,
overnight lows are expected to be mainly in the 70s.

&&

.AVIATION...
(06Z TAFS)
Issued at 1217 AM CDT Tue May 19 2026

An unsettled pattern will bring primarily MVFR overnight, with
some light to moderate showers possible through 12Z. Ceilings
briefly lift to VFR during the afternoon before MVFR returns
around sunset. Gusty southeasterly winds will prevail into
tomorrow, gusting around 25 kts.

At the very tail end of the current TAF cycle, there is a low
(less than 30%) chance of showers and thunderstorms at all sites,
with most likely timing after 06-09Z Wednesday.

&&

.MARINE...
Issued at 1106 PM CDT Mon May 18 2026

A Small Craft Advisory remains in effect till 9 AM CDT Tuesday due
to residual elevated wave heights. Outside of the threat for showers
and thunderstorms, Tuesday through Wednesday, adverse (Small Craft
Exercise Caution) conditions are likely. Again, outside of the
threat for showers and thunderstorms Wednesday night through next
Monday, marine conditions are expected to improve with moderate seas
and low to moderate winds.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             94  81  93  80 /  10  10  20   0
HARLINGEN               96  79  94  77 /  10  20  20   0
MCALLEN                 97  80  95  79 /  10  20  20  20
RIO GRANDE CITY         99  78  95  76 /  10  30  30  50
SOUTH PADRE ISLAND      86  81  85  81 /  10  10  20   0
BAYVIEW/PORT ISABEL     92  81  91  79 /  10  10  20   0

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk through this evening for TXZ451-454-455.

GM...Small Craft Advisory until 9 AM CDT this morning for GMZ130-132-
     135-150-155-170-175.

&&

SHORT TERM...23
LONG TERM....23
AVIATION...69-HK

Special Weather Statement
National Weather Service Brownsville TX
1226 AM CDT Tue May 19 2026

TXZ248-190615-
Zapata TX-
1226 AM CDT Tue May 19 2026

...STRONG THUNDERSTORMS WILL IMPACT NORTHERN ZAPATA COUNTY THROUGH
115 AM CDT...

At 1225 AM CDT, Doppler radar was tracking a cluster of strong
thunderstorms 9 miles southeast of El Cenizo, or 17 miles north of
San Ygnacio, moving southeast at 40 mph.

HAZARD...Wind gusts up to 50 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

Locations impacted include...
Bustamante.

This includes US Highway 83 between mile markers 738 and 746.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 2732 9937 2727 9933 2727 9896 2724 9895
      2697 9908 2712 9943 2713 9943 2715 9944
      2716 9943 2721 9943 2722 9944 2725 9944
      2727 9945
TIME...MOT...LOC 0525Z 295DEG 35KT 2728 9936

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH

Caceres

Special Weather Statement
National Weather Service Brownsville TX
121 AM CDT Tue May 19 2026

TXZ248>250-190700-
Brooks TX-Jim Hogg TX-Zapata TX-
121 AM CDT Tue May 19 2026

...STRONG THUNDERSTORMS WILL IMPACT NORTHERN JIM HOGG...NORTHWESTERN
BROOKS AND NORTHEASTERN ZAPATA COUNTIES THROUGH 200 AM CDT...

At 121 AM CDT, Doppler radar was tracking a cluster of strong
thunderstorms near South Fork Estates, or 7 miles west of
Hebbronville, moving southeast at 30 mph.

HAZARD...Wind gusts up to 50 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

Locations impacted include...
Hebbronville, Las Lomitas, Gruy Stadium, Randado, Thompsonville, Jim
Hogg County Airport, Hebbronville High School, South Fork Estates,
and Hebbronville Border Patrol Station.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 2734 9855 2734 9852 2727 9852 2726 9832
      2693 9867 2717 9909 2727 9898 2727 9880
      2735 9880 2735 9879 2736 9863 2734 9862
      2734 9859 2736 9859 2736 9855
TIME...MOT...LOC 0621Z 293DEG 27KT 2730 9879

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH

Caceres