textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 645 AM CDT Sun Jun 21 2026

- Additional heavy rain is possible during the early to late night hours tonight and WPC keeps nearly all of deep south Texas within a Slight Risk (Level 2 of 4) of possible scattered flash flooding from excessive and heavy rainfall until Sunday morning.

- Dry conditions resume Sunday and elevated moisture content leads to moderate to major heat risks (levels 2 and 3 of 4) through Tuesday, with SPSs possible for heat indices of 108-111 F.

- A moderate risk of life-threatening rip currents continues through Sunday afternoon, likely to persist and/or escalate to a high risk into the beginning of this upcoming week.

DISCUSSION

Issued at 1019 PM CDT Sat Jun 20 2026

The weak mid-level low, which has worked with instability and impressively high PWAT values to result in numerous SPSs for strong thunderstorms as well as several flash flood warnings and flood advisories over deep south Texas within the past 24-36 hours, remains in place over southern Texas and northeastern Mexico through tonight. At this time, all that is left of the active convection from today is an area of mostly light stratiform rain over the southern half of Hidalgo County. According to the latest SPC mesoanalysis and the RAP, there is still no capping inversion over deep south Texas and the GFS and HRRR continue to indicate the potential for showers and thunderstorms over the next 6 hours or so, with a low to medium (20-50%) chance of rain along/east of US-281 into the pre-dawn hours. As PWATs continue to range around 2.0 to 2.5 tonight, WPC maintains a Slight Risk of possible scattered flash flooding from excessive and heavy rainfall across all of deep south Texas tonight, with the exception of the barrier islands and extreme northwestern Zapata County, which are within a Marginal Risk of possible isolated flash flooding. By the pre-dawn to dawn hours Sunday morning, most of the convection is anticipated to diminish, reducing PoPs to a low (15-30%) chance by sunrise and dropping further throughout Sunday morning.

Throughout the day on Sunday and into Sunday night, high pressure aloft over the Baja Peninsula expands eastward to the Gulf and shifts/weakens the low pressure aloft southward, increasing subsidence and causing PWAT values to plummet to as low as around 1.35 in. by Monday morning, which is much drier than the average of around 1.7-1.8 in. for this time of year. Meanwhile, a series of mid-level shortwaves and surface lows traversing the Plains result in a tightened pressure gradient, enhancing lower-level moisture from onshore southeasterly winds gusting to 25-30+ mph each afternoon through the beginning of this upcoming week. Therefore, despite seasonably hot temperatures, rising to the mid/upper 90s in the afternoons and minimizing in the mid/upper 70s to lower 80s overnight, heat indices are likely to rise to around 105-111 F Sunday through Tuesday. An SPS for heat indices of around 108-111 F is possible during this time as moderate heat risks persist, with major heat risks possible over the coastal counties on Monday. Minor to moderate heat risks resume on Wednesday as southeasterly winds weaken and PWATs remain low before potentially rising at the end of next week.

A moderate risk of life-threatening rip currents continues through Sunday afternoon, likely to persist and/or escalate to a high risk into the beginning of this upcoming week.

AVIATION

(12Z TAFS) Issued at 645 AM CDT Sun Jun 21 2026

Light southeast winds and a mix of VFR/MVFR ceilings prevail across Deep South Texas early this morning. Southeast winds are forecast to increase and become moderate to gusty later this morning into the afternoon. VFR conditions will return around mid morning and continue through much of the period. MVFR ceilings may return late in the period.

MARINE

Issued at 1019 PM CDT Sat Jun 20 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 to southerly winds and moderate (4-6 ft) seas. A Small Craft Advisory is not out of the question Sunday night into Monday as winds peak to fresh to strong. Following, moderate to fresh winds resume Tuesday, with periods of SCEC possible through next weekend, when winds could re-enhance. Winds may ease just a bit into the middle of next week before picking back up towards and over the weekend. A low to medium (20-40%) chance of rain continues tonight, dropping to less than 10% throughout Sunday.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 93 83 95 82 / 20 0 0 0 HARLINGEN 94 80 96 80 / 20 0 0 0 MCALLEN 95 81 98 81 / 10 0 0 0 RIO GRANDE CITY 95 79 98 79 / 10 10 0 0 SOUTH PADRE ISLAND 89 84 90 84 / 20 0 0 0 BAYVIEW/PORT ISABEL 92 82 94 82 / 20 0 0 0

BRO WATCHES/WARNINGS/ADVISORIES

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