textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 1218 AM CDT Fri May 8 2026

Key Messages:

* There is a Marginal Risk (Level 1/5) of isolated severe thunderstorms and a Marginal Risk (Level 1/4) of isolated flash flooding Friday afternoon/evening across the Rio Grande Plains, Northern Ranchlands and the Upper RGV.

* These risks are conditional, but should severe thunderstorms develop, there is at least a 5% probability of large (1+ inch) hail, damaging winds (60+ mph) and excessive rainfall.

* A moderate risk of rip currents continues through Friday afternoon.

* Minor to Moderate (Levels 1/4 and 2/4) Heat Risks Friday through Sunday improve to a Minor Heat Risk on Monday and onward behind a weak cold front arriving late Sunday night or Monday morning.

DISCUSSION

Issued at 1027 PM CDT Thu May 7 2026

Another day, another complex and constantly evolving forecast in regards to unsettled weather expectations across Deep South Texas tonight through Saturday, resulting from increasing forcing and embedded impulses ahead of a cut-off upper level low/trough moving eastward across northern Mexico. Observations as well as satellite and radar imagery this afternoon and evening have revealed a stalled boundary south of the border providing convergence and lift for deep and strong to severe thunderstorms over the Sierra Madre, weakening as they move northeastward and into the capping inversion in place over our region. Yet, light to moderate rain, occasionally heavy, has made it into the Rio Grande Plains, western portions of the Northern Ranchlands and the Upper RGV so far. Throughout this time, hourly updates of the HRRR have adjusted well to best reflect instability and radar, projecting for Sierra Madre convection to gradually decrease from north to south overnight, thus decreasing rain chances further northwest while increasing southeastward into late tonight and Friday morning, with the best chances generally along/west of I-69 E. At this point in time, we anticipate for any thunderstorms making it to the border to be sub-severe due to the capping inversion though there could be lightning at times closer to the Rio Grande. Overnight lows in the 70s are expected.

How long showers and cloud cover persist Friday morning, how far north lower level southeasterly winds push the frontal boundary as a warm front and the degree of destabilization that follows will most likely determine the potential and intensity of convection developing over the Sierra Madre Friday afternoon and whether or not it makes it into the CWA in the late afternoon or evening hours as the trough-associated large scale ascent increases. At this time, SPC places a Marginal Risk (Level 1 of 5) of isolated severe thunderstorms and WPC maintains a Marginal Risk (Level 1/4) of flash flooding across the Rio Grande Plains, the Upper RGV and most of the Northern Ranchlands. Due to the reasons provided above, this remains a conditional risk since it is possible that cloud cover lingers into Friday and more stable air prevents stronger storms from developing. However, if instability and frontal lift return in time to develop deep and strong to isolated severe convection, then there would be at least a 5% probability of large (1+ inch) hail, damaging winds (60+ mph) and excessive rainfall across these areas later in the day. In short, there is a low to medium (20-40%) chance of rain during the daytime along/east of US-281 on Friday, increasing late Friday afternoon to as much as a low to medium (30-60%) chance along/west of US-281 Friday evening. Following, a low to medium (20-40%) chance of rain continues into Saturday afternoon before diminishing overnight as the trough exits and weakens over the Gulf. Most of Deep South Texas can expect around 0.2-0.5 of an inch of rain through Saturday afternoon, while areas in and near the Rio Grande Plains could receive up to an inch of rain, or more.

Temperatures rise Friday afternoon into the upper 80s/lower 90s. A Minor Heat Risk, with heat indices around 95-100 F, is likely along/west of I-69 E while points further east experience a Moderate Heat Risk as afternoon apparent temperatures peak around 100-105 F. The return of southeasterly winds increase temperatures by a few degrees over the weekend, with Minor to Moderate Heat Risks (indices of 95-105 F) continuing through Sunday. Surface high pressure pushes a weak cold front into our region late Sunday night or early Monday morning. This will do little to cool temperatures, but temperatures in the 80s/90s and drier air are likely to result in a Minor Heat Risk on Monday into the middle of next week, featuring only a slight warming trend.

A moderate risk of rip currents continues through Friday afternoon.

AVIATION

(06Z TAFS) Issued at 1218 AM CDT Fri May 8 2026

While a mixture of IFR and MVFR conditions are expected for the next several hours, by sunrise conditions should be more MVFR with the increasing ceilings. While some chances for showers and an isolated thunderstorm could occur within the next several hours, by sunrise those chances decrease again. By late morning or early afternoon, the ceilings should rise even further allowing for VFR conditions. However, cloud cover is still expected to linger over the region. Light southeasterly winds are expected through the period.

MARINE

Issued at 1027 PM CDT Thu May 7 2026

Gentle to moderate northeasterly winds and moderate (3-5 ft) seas tonight become southeasterly with slight to moderate (2-4 ft) seas on Friday. A weak cold front arrives either late Sunday night or Monday morning, resulting in moderate northeasterly winds and moderate seas on Monday, gradually returning to gentle to moderate southeasterly winds and slight to moderate seas by the middle of next week. Chances of rain gradually increase to a low (15-30%) overnight tonight into Friday morning and then increase again to a low to medium (20-40%) chance on Saturday. Drier conditions resume Saturday night.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 91 77 90 77 / 30 10 20 0 HARLINGEN 91 74 90 73 / 30 10 30 0 MCALLEN 91 75 91 75 / 40 20 30 0 RIO GRANDE CITY 89 74 90 74 / 20 40 40 0 SOUTH PADRE ISLAND 83 78 83 78 / 30 10 20 0 BAYVIEW/PORT ISABEL 89 76 88 76 / 30 10 30 0

BRO WATCHES/WARNINGS/ADVISORIES

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