textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 1246 PM CDT Wed May 20 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.

* Storm Prediction Center has a marginal risk (level 1 of 5) for Zapata and the western portions of Starr and Jim Hogg. The rest of the region is in a general thunderstorm outlook.

* Weather Prediction Center has a marginal risk (level 1 of 4) for Zapata, most of Jim Hogg, northwestern Starr, and northwestern Brook counties for excessive rainfall.

DISCUSSION

Issued at 1246 PM CDT Wed May 20 2026

Even though an active line of showers and thunderstorms moved through the region this morning, there is a possibility that another round of showers and thunderstorms could move through the region tonight off of the Sierra Madre. Several CAMs shows that there is another system that could develop during the overnight hours. This could be another round of strong to severe thunderstorms for Deep South Texas and the Rio Grande Valley. It should be noted as of the time of writing, that SPC does have Zapata and the western portions of Starr and Jim Hogg in a marginal risk (level 1 of 5) for severe weather tonight, while the rest of the area is in a general thunderstorm outlook. This is just to highlight were the more likely area to be impacted by severe weather is, but does not limit it to that region. On top of this, WPC does have Zapata, most of Jim Hogg, northwestern Starr, and northwestern Brooks in a Marginal Risk (level 1 of 4) for excessive rainfall tonight.

The rest of the period can generally be summarized as on and off periods of rain. While some of these showers and thunderstorms could produce heavy rainfall and some localized flooding based on the environmental set up. Southwesterly flow aloft along with some shortwaves moving over the Sierra Madre, southeasterly flow at the surface to bring in moisture from the Gulf, and a frontal boundary stalled to the north. WPC does have Deep South Texas and the Rio Grande Valley in a marginal risk of excessive rainfall for days 2, 4, and 5 with days 2 and 4 having a slim part of northern Kenedy in a slight (level 2 of 4). Most likely rainfall amounts could be in the range of 2 to 2.5 inches for the Northern Ranchlands while areas in the Lower Valley could see 1 to 2 inches. However, there is a low chance (10%) that we could see rainfall totals near 3 to 4 inches for the Northern Ranchlands with 2 to 3 inches possible in the Lower Valley.

As for the temperatures, the high temperatures should generally be in the range of the upper 80s to lower 90s for the majority of the forecast period. While the lows are in the 70s.

AVIATION

(18Z TAFS) Issued at 1246 PM CDT Wed May 20 2026

VFR ceilings are expected for the majority of the afternoon and early evening hours, even though there will be some lingering clouds over the area. MVFR ceilings do return tonight as a low- level cloud deck moves over the area. PROB30 groups have been used to try to time possible showers and thunderstorms moving over the area as they could move west to east during the overnight hours. MFE is likely to see impacts shortly after midnight and it will take a few hours for HRL and then BRO to see those impacts as well. It is possible that heavy downpours from these storms reduce visibilities to LIFR at times. Light easterly wind are expected for the large portion of the TAF cycle at all TAF sites, although a few gusts up to 20 knots are possible at HRL.

MARINE

Issued at 1246 PM CDT Wed May 20 2026

Showers and thunderstorms over the Lower Texas Coast are expected to be the biggest hazard for forecast period. Rain chances remain near medium (50%) each day. Showers and thunderstorms will be capable of producing heavy downpours that will reduce visibilities and locally elevated winds and seas.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 78 89 78 92 / 40 50 30 10 HARLINGEN 75 88 75 92 / 40 50 20 20 MCALLEN 76 89 76 94 / 40 50 30 20 RIO GRANDE CITY 73 89 74 94 / 60 50 40 10 SOUTH PADRE ISLAND 79 84 80 86 / 30 50 30 10 BAYVIEW/PORT ISABEL 77 88 78 91 / 30 50 30 20

BRO WATCHES/WARNINGS/ADVISORIES

TX...None. GM...None.