textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 617 AM CDT Tue Jun 16 2026

- Scattered to numerous flash floods are possible overnight into Tuesday, some may be significant. Heavy Rain with the potential for significant flash flooding is likely for Deep South Texas tonight through Wednesday, with rainfall rates between 2 to 4 inches an hour possible. A Flood Watch remains in effect through Thursday morning.

- There is a Moderate (level 3 of 4) Risk of Excessive Rainfall across all of Deep South Texas overnight. There is a Slight (level 2 of 4) to Moderate (level 3 of 4) Risk of Excessive Rainfall across the area Tuesday and Tuesday night. A Marginal to Slight Risk of Excessive Rainfall continues across the eastern portions of Deep South Texas, mainly along and east of US 281/I-69C, Wednesday and Wednesday night. - Heat Risk continues through the remainder of the week and into the weekend. A Moderate to Major (levels 2-3 of 4) Heat Risk is forecast Thursday and Friday. Heat Advisories may be needed Wednesday becoming more likely Thursday and Friday.

- The National Hurricane Center continues a medium chance (50%) of tropical development over the northwestern Gulf over the next 7 days.

DISCUSSION

Issued at 1049 PM CDT Mon Jun 15 2026

Heavy rainfall with the potential for significant flash flooding is likely across the Rio Grande Valley and Deep South Texas overnight into Tuesday. The potential for isolated to scattered flash flooding will continue through early Thursday. A low pressure system over Mexico will move northeast over Deep South Texas and interact with deep tropical moisture. This will create a favorable environment for slow-moving heavy showers and thunderstorms with rainfall rates of 2 to 4 inches per hour possible overnight into early Tuesday. This evening's 0Z Brownsville sounding indicated a PWAT value of 2.24 inches.

Latest Brownsville radar indicates a few clusters of showers and thunderstorms moving north to northeast across the CWA. Moreover, widespread light to moderate showers with some embedded thunderstorms continue across other portions of Deep South Texas. Some of the latest CAMS, particularly the RAP/HRRR, suggests that the current activity will continue to move northeast or east off or along the Lower Texas Coast with additional development across the area Tuesday afternoon.

Rain chances are forecast to remain high (80-90%) overnight given the high moisture content and lift in place. High (80-90%) rain chances continue most of Tuesday with rain chances (30-60%) decreasing from west to east late Tuesday afternoon. Low to medium (10 to 40%) rain chances Tuesday evening, mainly near the coast, continue to decrease through the night into Wednesday as the 500mb trough axis swings eastward. A few lingering showers and thunderstorms will be possible on Wednesday, mainly along the coast. Otherwise, rain-free conditions return across the region on Wednesday.

The weak surface trough/low currently over northeastern Mexico may re-emerge over the northwest Gulf late Tuesday into Wednesday. The National Hurricane Center has a 50% chance for tropical development through day 7. Any development at that point would likely have minimal impact on Deep South Texas. However, some increased swell along the coast is possible, which could result in minor coastal flooding and increased rip current risk.

The increased cloud cover and rain chances will lead to slightly lower daytime temperatures through midweek. Drier weather returns on Thursday as high humidity continues. There is a Moderate to Major (levels 2-3 of 4) Heat Risk Thursday and Friday with a Moderate Heat Risk this weekend. Heat Advisories may be needed Thursday and Friday.

AVIATION

(12Z TAFS) Issued at 617 AM CDT Tue Jun 16 2026

Major convection is ending across the region, leaving -RA behind. However, a TEMPO remains in the TAFs for the afternoon hours in the event convection develops again. Drier weather should settle into the region tonight. Light to moderate winds and mostly cloudy skies will also occur.

MARINE

Issued at 1049 PM CDT Mon Jun 15 2026

Slightly adverse to adverse marine conditions are forecast tonight into Tuesday as low pressure over the area. Small Craft Exercise Caution conditions are expected on the Gulf waters tonight and on the Laguna Madre on Tuesday. Showers and thunderstorms will continue along the Lower Texas Coast and the Gulf waters tonight through mid to late week. Adverse to hazardous conditions could return Wednesday into Friday night as low pressure moves off Texas Coast. Small Craft Advisories or Small Craft Should Exercise Caution headlines will likely be needed.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 84 77 94 83 / 90 40 20 0 HARLINGEN 83 74 93 79 / 90 30 20 0 MCALLEN 84 77 94 81 / 90 20 10 0 RIO GRANDE CITY 85 74 95 78 / 90 10 0 0 SOUTH PADRE ISLAND 85 79 90 84 / 90 40 30 0 BAYVIEW/PORT ISABEL 84 76 93 81 / 100 40 30 0

BRO WATCHES/WARNINGS/ADVISORIES

TX...Flood Watch through Wednesday morning for TXZ248>255-351-353>355- 451-454-455.

GM...None.