Update AFD Area Forecast Discussion — Sat Apr 4, 2026 4:06 PM

AFDBRO

Area Forecast Discussion...CORRECTED
National Weather Service Brownsville TX
258 PM CDT Sat Apr 4 2026

...New DISCUSSION, MARINE...

.KEY MESSAGES...
Updated at 212 PM CDT Sat Apr 4 2026

Key Messages:

 * Cold front passes through Deep South Texas from northwest to
   southeast from late this afternoon/early this evening into the
   early/mid morning hours tomorrow, bringing showers and
   thunderstorms continuing through tomorrow night.

 * The Storm Prediction Center (SPC) has highlighted a Marginal
   Risk (Level 1/5) of isolated severe thunderstorms along/west
   of US-281, with the primary concerns being large hail and
   damaging winds.

 * The Weather Prediction Center (WPC) includes all of our County
   Warning Area (CWA) within a Marginal Risk (Level 1/4) of
   isolated flash flooding for tonight and tomorrow.

 * 1 to 3 inches of rain are likely tonight through Sunday night,
   with the highest chances across the Rio Grande Plains and
   Upper RGV, where rainfall totals may exceed 3 inches.

 * A medium risk of rip currents continues through tomorrow
   afternoon and marine/coastal conditions are likely to become
   adverse tomorrow and into the beginning parts of next week.

&&

.DISCUSSION...
Issued at 212 PM CDT Sat Apr 4 2026

The main driver of the impending unsettled weather is a cut-off low
and potent surface low pressure system moving eastward across the
Upper Midwest, extending a cold front southwestward, moving into
South Texas throughout this afternoon. Ahead of the front, lower
level southeasterly flow maintains moisture and warm air advection
into the region today, with temperatures maximizing in the
mid/upper 90s, which adds to the instability across the CWA, with
SBCAPE values ranging from around 1,000-2,500+ J/Kg into the early
evening hours, per the RAP. Meanwhile, instability aloft enhances
ahead of a mid-level disturbance approaching from the west,
increasing MUCAPE to upwards of 1,000 J/Kg, likely surpassing
2,000 J/Kg along/west of US-281, where thermodynamic profiles
further suggest mid-level lapse rates of 6.5 deg C/Km and inverted
Vs despite weaker shear; as the front arrives into the northern
and western portions of the CWA later this afternoon or early
evening, moisture pooling combines with instability and enhancing
frontal lift to result in scattered to numerous showers and
thunderstorms. In consideration of the convective parameters
discussed above, CAMs continue to suggest a growing likelihood of
embedded isolated strong to severe thunderstorms this evening and
into the early nighttime hours tonight along and west of US-281,
where SPC has included a Marginal Risk (level 1/5) for isolated
large hail and damaging wind gusts in excess of 60 mph. The severe
risk is likely to steadily drop off through the overnight hours
as instability and mid-level lapse rates decrease. If the front
arrives earlier and/or pushes through faster within this time
frame, the chance of severe thunderstorms could be maximized
whereas a later and slower arrival could delay and/or minimize
severe potential. CAMs still indicate a lower chance of embedded
isolated strong storms, with the potential for small hail and
stronger gusts, east of US-281 and into Lower RGV into the late
night and early morning hours tomorrow.

Along with the potential for strong to severe thunderstorms is the
expected heavy rain spreading east-southeastward across the
remainder of Deep South Texas overnight tonight as rain chances
increase to as much as a medium to likely (60-80%) chance late
tonight through most of Sunday night. WPC includes all of our region
within a Marginal Risk (level 1/4) for isolated flash flooding for
tonight and tomorrow; CAMs are in agreement with the most torrential
rainfall shifting from northwest to southeast from late this
afternoon or early evening into tomorrow morning ahead of and along
the frontal boundary, with the most prolific rainfall rates
occurring further west. Yet, as the mid-level disturbance passes
through late tonight and into tomorrow, further rounds and/or
training of moderate to heavy rainfall is likely. Further west,
the sudden onset of heavy rain and rapid runoff draws attention to
a more critical risk of flask flooding, particularly in the
hillier regions of Zapata and Starr County, which was impacted
severely by flooding rains last month. Further east and across the
more flat and populated areas, the greater concern is for
hydroplaning and minor nuisance flooding of low-lying areas along
with isolated instances of flash flooding. By Monday morning, most
of the region is likely to have received near at least 1 inch of
rain, with 2-3 inches across western portions of the Northern
Ranchlands, the Rio Grande Plains and Upper RGV. At this time, the
NBM still indicates a 30-40% chance of at least 2 inches of rain
along/east of US-281 and a 40-70% chance further west, highest
across western portions of the Northern Ranchlands, Rio Grande
Plains and the Upper RGV, where there is a 15-30% chance of totals
surpassing 3 inches by Monday morning.

Following, chances of rain gradually decrease across much of Deep
South Texas on Monday, though coastal troughing and additional
weaker mid-level disturbances could keep a low (15-30%) chance of
rain across portions of the RGV and near/along the immediate
coastline into Wednesday. Additional shortwaves aloft may bring
further low (15-30%) chances of rain across the region into the
later parts of next week as well, though confidence is low to medium
at this time. Temperatures gradually increase from the 60s/70s
tomorrow and Monday back to the 80s by Wednesday as clouds decrease
and southeasterly winds return. Overnight lows also warm from the
50s tomorrow night and Monday night back to the 60s by Wednesday
night.

A medium risk of rip currents continues through tomorrow afternoon
and coastal conditions are likely to become adverse tomorrow and
into the beginning parts of next week.

&&

.AVIATION...
(18Z TAFS)
Issued at 1236 PM CDT Sat Apr 4 2026

VFR conditions with scattered high clouds and breezy south-
southeasterly winds of around 10-15 knots, are expected to
continue through late this afternoon, with gusts up to 20-25
knots, occasionally higher, likely. Later this afternoon or this
evening, showers and thunderstorms develop ahead of and along a
cold front, expected to pass through all terminals and shift
winds out of the north to northeast by mid-morning tomorrow, noted
in the PROB 30s. As the convection arrives, there is the potential
for isolated strong to severe thunderstorms, bringing a low chance
of large hail and very strong wind gusts in excess of 55 knots,
with the greatest probability being at KMFE during the evening to
early nighttime hours. Overnight, convection spreads east to KHRL
and then KBRO, where there remains the potential for moderate to
strong wind gusts and possibly small hail. Along with these risks
is the likelihood for MVFR or IFR ceilings, or lower, as the
convection moves through with not much recovery following into the
daytime tomorrow.

&&

.MARINE...
Issued at 212 PM CDT Sat Apr 4 2026

Moderate easterly to southeasterly winds and moderate (3-4 ft) seas
continue into the early nighttime hours, when a cold front arrives,
passing through into the morning hours tomorrow, bringing fresh to
strong northerly to northeasterly winds and moderate (6-7 ft) seas,
persisting into Monday; a Small Craft Advisory goes into effect
for all Lower Texas coastal waters from 7 AM Sunday until 1 PM
Monday afternoon. Winds gradually ease throughout the remainder of
Monday afternoon with gentle to moderate northeasterly winds
becoming easterly on Wednesday and southeasterly on Thursday.
Small Craft Exercise Caution conditions are possible again later
next week as a pressure gradient tightens and results in moderate
to fresh southeasterly winds and moderate seas.

As the front arrives tonight, there is the possibility of isolated
strong thunderstorms into tomorrow morning, with the potential for
small hail and stronger wind gusts as chances of rain increase to as
much as a medium to likely (60-80%) chance tomorrow. Following, a
low (15-30%) chance of rain lingers into much of next week as a
result of warm advection showers and additional disturbances
aloft.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             70  76  59  69 /  70  90  90  60
HARLINGEN               64  74  55  71 /  70  90  80  50
MCALLEN                 66  72  59  70 /  80  90  80  40
RIO GRANDE CITY         60  68  55  66 /  90  90  80  40
SOUTH PADRE ISLAND      71  75  64  70 /  70  90  90  70
BAYVIEW/PORT ISABEL     67  77  59  71 /  70  90  90  60

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$