textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 227 PM CDT Sat May 23 2026

Key Messages:

- A Flood Watch is in effect until Monday morning. There is a chance of isolated to scattered flash flooding in areas that receive heavier rainfall through Sunday.

- The Storm Prediction Center as all of Deep South Texas under a Marginal Risk (level 1 of 5) for severe weather through Sunday morning. - A moderate risk of rip currents continues through Sunday evening.

DISCUSSION

Issued at 227 PM CDT Sat May 23 2026

An unsettled and active weather pattern will remain in place through the middle of next week across Deep South Texas as embedded disturbances continue to traverse the westerly to northwesterly flow aloft. There is a potential for strong to severe thunderstorms and locally heavy rainfall, but the exact timing of any convection and rainfall amounts remain uncertain.

This afternoon/evening and Tonight: Deep South Texas will remain under the influence of an upper level shortwave traversing the state, providing ample forcing for ascent. Additionally, forecast model soundings and the 12Z BRO sounding indicate a deep moisture profile, with PWATs upwards of 1.9 inches. Despite this mornings convection stabilizing the atmosphere early this afternoon, there should be some destabilization once again later this afternoon, especially over northern Mexico and our far western counties. In combination with forcing for ascent, convection may develop late this afternoon and evening. High resolution guidance has not been handling this setup the best, but given the current environment - MLCAPE values around 2000-3000 J/kg, 0-6km wind shear around 35-40 knots, mid level lapse rates around 6-7 C/km, and PWATs upwards of 1.9-2 inches - may support additional shower and thunderstorm development and attempt to make their way towards the Gulf. The main threat with any severe thunderstorms that develop will be capable of damaging wind gusts. Additionally, the environment is favorable for efficient rain-producing showers and thunderstorms, with rain rates of 2-2.5/hr. This may result in localized flash flooding issues, especially across portions of the region that received heavy rainfall this morning. A Flood Watch remains in effect through Monday morning.

The best forcing for ascent will shift to the north and northeast as the shortwave translates towards the Southern Plans by Sunday, but isolated showers and thunderstorms may develop especially during the late morning to late afternoon hours as diurnal instability increases. Rain chances range from around 20-50%, with the best chances along and east of US-281. The rest of the week, including Memorial Day, remain unsettled with low to medium chances for showers and thunderstorms. There is still uncertainty among guidance on the timing of embedded disturbances and an approaching upper level trough from the western US. However, the environment will be favorable for strong to severe thunderstorms and locally heavy rainfall.

AVIATION

(18Z TAFS) Issued at 227 PM CDT Sat May 23 2026

The main aviation concern is the potential for strong to severe convection this afternoon and overnight across the region as a shortwave interacts with favorable moisture content and instability.Additional rounds of showers and thunderstorms may develop overnight and into early Sunday morning. The main threats with any strong to severe thunderstorms are damaging wind gusts, small hail, locally heavy rain, and lightning. Additionally, brief MVFR/IFR ceilings and visibility will likely occur within any convection. There remains uncertainty in the timing of convection at the airports, which may result in amendments throughout the forecast period.

MARINE

Issued at 227 PM CDT Sat May 23 2026

Generally favorable winds and seas are expected to persist through the forecast period. However, near daily chances for showers and thunderstorms will continue into the middle of next week. Saturday and Sunday will likely feature the highest rain/storm chances, around 40-70%. These storms may produce heavy rainfall, frequent lightning, strong winds, and locally higher seas.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 77 90 75 89 / 40 50 20 30 HARLINGEN 73 89 71 88 / 30 40 10 30 MCALLEN 75 90 74 90 / 30 30 20 30 RIO GRANDE CITY 72 90 72 90 / 20 20 30 20 SOUTH PADRE ISLAND 79 84 78 83 / 40 40 20 20 BAYVIEW/PORT ISABEL 76 88 75 87 / 30 40 20 20

BRO WATCHES/WARNINGS/ADVISORIES

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

GM...None.