textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 1242 AM CDT Sat Jun 20 2026

- Slightly cooler, but still dangerous, heat indices and moderate to major heat risks (levels 2 and 3 of 4) continue into the beginning of next week, with SPSs for heat indices of 108 to 111 F still possible, especially on Sunday and Monday.

- WPC includes the southeastern and eastern portions of Jim Hogg and Starr counties and all areas eastward within a Marginal Risk (level 1 of 4) of possible isolated flash flooding as well as a Slight Risk (level 2 of 4) of possible scattered flash flooding for areas further west tonight in addition to a Marginal Risk of isolated flash flooding for all of deep south Texas on Saturday.

- Drier conditions resume on Sunday along with seasonably hot temperatures and minor (level 1 of 4) to moderate heat risks by Wednesday as afternoon heat indices cool slightly to around 100-110 F.

- A medium risk of life-threatening rip currents continues through Saturday afternoon.

DISCUSSION

Issued at 1055 PM CDT Fri Jun 19 2026

We'll start off by focusing on the heat, which has been extreme over the last several days. Although temperatures are likely to remain seasonably hot in comparison to this past Wednesday and Thursday, maximizing and minimizing in the mid/upper 90s and upper 70s/lower 80s, respectively, relative humidity values remain very moist into the beginning of next week, with widespread moderate heat risks likely through Tuesday. Therefore, SPSs for heat indices of 108-111 F are certainly possible, especially on Sunday and Monday when clouds clear and major heat risks expand over portions of the coastal counties. A Heat Advisory is not fully out of the question as well. The potential for an SPS on Saturday is still up in the air at this time and will be dependent on how convection tonight plays out; an SPS may be issued either late tonight or Saturday morning. Otherwise, afternoon heat indices generally trend cooler by the middle of next week, ranging from 100 to 110 F.

Now for the weather pattern: a weak mid/upper level shortwave and trough extending into northeastern Mexico and south Texas, wedged between a high pressure aloft over the eastern Pacific and over the Gulf, have led to a broken line of showers and thunderstorms slowly moving eastward over Zapata and into the Upper RGV and Northern Ranchlands, producing heavy rain. A few stronger thunderstorms have led to SPSs over the Corpus Christi CWA as well as portions of Zapata and Jim Hogg counties this evening, for strong winds up to 40 mph and the potential for pea-size hail, resulting from better forcing aloft. The Latest HRRR runs continue this activity further east before largely dissipating late tonight as it approaches the US- 281 corridor. Yet, there is still a chance, though low confidence, that convection could keep developing further east and south overnight; low to medium (30-60%) chances of rain further north and west decrease overnight, though expand to a low (15-30%) chance across most of deep south Texas by Saturday morning. Due to high PWATs (> 2.0 in.)in place, heavy rain is likely to continue for much of tonight. Therefore, WPC has expanded the Slight Risk of possible scattered flash flooding tonight to as far east as the northern and western half of Jim Hogg and the far western portions of Starr counties as well as a Marginal Risk of possible isolated flash flooding eastward to the coast.

On Saturday, a plume of deep, tropical moisture moves over the CWA, surging PWATs to 2.0-2.5 in., with pockets of 2.7+, possible. Although weaker bulk shear values are anticipated, lowering heights, weakened subsidence aloft could help to generate scattered pop-up showers and thunderstorms, all capable of producing heavy rain; WPC highlights a Marginal Risk of possible isolated flash flooding across all of deep south Texas on Saturday from excessive and heavy rainfall. Still dependent on how convection evolves overnight, outflow boundaries could generate more numerous convection along/east of US-281, where there is a low to medium (30-50%) chance of rain and slightly lower elsewhere (20-40%). Chances of rain gradually diminish east to west throughout Saturday evening.

High pressure aloft takes over by Sunday, leading to drier conditions, with chances of rain below 10% through next Friday.

A moderate risk of life-threatening rip currents continues through Saturday afternoon.

AVIATION

(06Z TAFS) Issued at 1242 AM CDT Sat Jun 20 2026

Light southeast to south winds and VFR ceilings prevail across much of Deep South Texas early this morning. A mix of VFR/MVFR conditions will likely continue overnight with full VFR conditions expected to return mid to late morning. There is a low to medium (20-40%) chance of isolated to scattered showers and thunderstorms. The latest CAM models, especially the HRRR, suggest that some showers and thunderstorms may develop mid to late morning. Brief MVFR conditions will be possible in and around any convection. Light southeast to south winds overnight are forecast to increase and become moderate in the afternoon. MVFR conditions may return late in the period.

MARINE

Issued at 1055 PM CDT Fri Jun 19 2026

Small Craft Exercise Caution (SCEC) conditions are likely to continue through at least Monday night as a tightened pressure gradient results in moderate to fresh, occasionally strong, southeasterly winds and moderate (4-6 ft) seas. Winds may ease just a bit into the middle of next week before picking back up towards and over the weekend. Aside from a low (15-30%) chance of showers and thunderstorms late tonight, continuing through Saturday night, dry conditions prevail.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 93 83 94 83 / 30 10 10 0 HARLINGEN 93 80 95 80 / 40 20 0 0 MCALLEN 94 82 96 82 / 40 30 10 0 RIO GRANDE CITY 94 79 98 80 / 40 30 10 0 SOUTH PADRE ISLAND 88 84 89 84 / 30 10 10 0 BAYVIEW/PORT ISABEL 91 82 93 82 / 30 10 10 0

BRO WATCHES/WARNINGS/ADVISORIES

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