textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 633 PM CDT Sat Apr 18 2026

Key Messages:

* A cold front is expected Saturday night into Sunday morning which will bring moderate to high (60-90%) chances for rain through Tuesday morning. There is a moderate (40-50%) percent chance of rain Tuesday and Tuesday night.

* Most areas should receive between 1 and 2 inches of rain, but some areas could see locally heavier amounts of 3 to 4 inches. Isolated flash flooding is possible in low-lying or poor drainage areas that receive heavier rainfall.

* Temperatures will fall 15-30 degrees into Sunday morning. * A high risk of rip currents is expected over the weekend with elevated surf and minor coastal flooding near high tide cycles. High Surf and Coastal Flood Advisories have been issued for Sunday morning starting at 11z.

* A Small Craft Advisory is in effect starting at 06z Sunday through 03z Monday.

DISCUSSION

Issued at 1239 PM CDT Sat Apr 18 2026

Conditions will be warm and dry for the rest of the afternoon until showers and perhaps a few thunderstorms start moving into Deep South Texas around 0z this evening ahead of an approaching frontal system. The front is expected to reach all the way through the region overnight into Sunday, with a coastal low developing just offshore. The coastal low is expected to hang around a few days, with the frontal boundary lifting back north and stalling over the Lower Rio Grande Valley by Monday. This will support moderate to high precipitation chances from this evening through Tuesday.

Rain chances are highest tonight as the front makes its way through the region, with chances ranging between 60 to 85%. Despite trending slightly lower that previous guidance suggested, Sunday's rain chances are still moderate to high (60 to 70%). This continues through Monday night, until chances start to decrease on Tuesday and Tuesday night (40 to 50%) as the frontal boundary and the coastal low start to diminish. Conditions should dry out again by Wednesday and remain dry through the remainder of the week.

Most likely rainfall amounts from this system should range between 1 and 2 inches for most places, with some areas receiving closer to 3 to 4 inches in areas of locally heavier rainfall. Due to the unusually moist atmospheric profile, the Weather Prediction Center has the entire region under a marginal (level 1 of 4) risk of excessive rainfall for Sunday, and parts of Willacy, Brooks, and Kenedy Counties for Monday. Though most rain is expected to be beneficial, there is be a small (5%) chance for nuisance and isolated flash flooding in low-lying and poor-drainage areas.

After the frontal passage, temperatures will stay unseasonably cool Sunday and Monday before warming back to seasonal levels by Tuesday. Most areas west of I-69C will stay below 70 degrees for Sunday, but areas closer to the coast will see daytime highs in the mid-70s. Overnight lows Sunday night will be in the upper 50s/lower 60s. A warming trend will commence Monday as the frontal boundary retreats to the north, and temperatures should reach seasonal levels again by Tuesday. By the end of next week, temperatures will be unseasonably warm again with dry conditions.

Hazardous coastal conditions are also expected with this cold front, including life-threatening rip currents and elevated surf, as well as some potential beach run-up near high tide cycles, as astronomical tides begin to increase over the weekend. For this reason, a High Surf Advisory and a Coastal Flood Advisory have been issued starting at 11z tomorrow.

AVIATION

(00Z TAFS) Issued at 633 PM CDT Sat Apr 18 2026

Moderate to gusty southeast winds with a mix of low to mid level clouds prevail across Deep South Texas early this evening. BRO radar currently indicates a line of light to moderate SHRA associated with a cold front near HBV to 67R. VFR conditions are expected ahead of the front at all RGV terminals. FROPA is forecast around 03Z at MFE and near 06Z for BRO. Winds will shift to the north with ceilings lowering to MVFR to IFR in the wake of the front. Light rain with a few thunderstorms will be possible along and ahead of the cold front. Periods of light to moderate RA/-DZ and BR will develop overnight into Sunday. MVFR ceilings and/or visibilities may lower to IFR/LIFR Sunday morning into the afternoon.

MARINE

Issued at 1239 PM CDT Sat Apr 18 2026

Due to a tightened pressure gradient, SCEC conditions are ongoing in the Bay and the Gulf waters and are expected to slightly improve this evening before Small Craft Advisory conditions are expected to develop again by 06z Sunday morning as a cold front passes through the area. A Small Craft Advisory is now in effect starting at 06z overnight and should last until Sunday evening. Once conditions improve, SCEC conditions are still possible through Monday night and intermittently throughout the week.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 66 75 66 78 / 70 70 80 70 HARLINGEN 63 73 62 78 / 60 70 70 70 MCALLEN 63 70 62 77 / 80 70 80 60 RIO GRANDE CITY 59 66 58 74 / 80 70 70 60 SOUTH PADRE ISLAND 71 75 70 76 / 70 70 80 70 BAYVIEW/PORT ISABEL 66 75 65 79 / 60 70 70 70

BRO WATCHES/WARNINGS/ADVISORIES

TX...Coastal Flood Advisory from 6 AM to 1 PM CDT Sunday for TXZ451- 454-455.

High Surf Advisory from 6 AM to 7 PM CDT Sunday for TXZ451-454- 455.

GM...Small Craft Advisory from 1 AM to 10 PM CDT Sunday for GMZ130- 132-135-150-155-170-175.