textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 135 PM CDT Mon Jun 15 2026

* Heavy Rain with the potential for significant to catastrophic flash flooding is likely for Deep South Texas the rest of today through Wednesday, with rainfall rates between 2 to 5 inches an hour possible. A Flood Watch is in effect into Thursday morning.

* Most areas should expect to receive between 5-10 inches of rain between now and Thursday morning, with some localized areas receiving 12+ inches. Avoid unnecessary travel, as flooding conditions can escalate quickly.

* The National Hurricane Center has increased chances of development off the Texas Coast from 30% to 50% for the next 7 days as today and tomorrow's convection moves offshore.

* Heat Risk continues through the remainder of the week. The worst day will be Thursday, with Major (level 3 of 4) Heat Risk Expected and Heat Advisories likely needed. Some areas could also reach Heat Advisory criteria Wednesday afternoon.

* A Moderate Risk of Rip Currents will continue through tomorrow. This risk could potentially increase throughout the week.

DISCUSSION

Issued at 135 PM CDT Mon Jun 15 2026

Heavy rain with the potential for catastrophic flash flooding is highly possible in the Rio Grande Valley and Deep South Texas over the next few days. Avoid unnecessary travel today through Wednesday if possible, as roadways can become quickly flooded in areas where heavy rainfall occurs (as has already been observed in portions of the central Rio Grande Valley this morning).

The Weather Prediction Center has all of Deep South Texas under a Moderate Risk (level 3 of 4) of excessive rainfall for the remainder of today into this evening, and keeps the Moderate Risk for the eastern portion of the CWA tomorrow. The Western portion of the CWA is under a Slight (level 2 of 4) Risk of excessive rainfall tomorrow, and the Coastal Counties remain under a Slight Risk of Excessive rainfall on Wednesday. Rainfall rates of anywhere between 2 to 5 inches per hour are possible with these showers and thunderstorms, and we are likely to see areas of training convection (ie, the same areas receiving multiple rounds of heavy rain) due to the overrunning nature of the convective setup.

A very slow-moving cold front remains draped over Central Texas this afternoon, and the air remains richly saturated with very high PWATs expected (over 2.5 inches in some areas), due to a combination of upper level tropical moisture from Pacific storm remnants and rich surface moisture being advected from a warm Gulf. In addition, there is the presence of a mid to upper level low that is expected to move directly across the area over the next few days along with a surface trough, which will add to the instability and the rain potential. Southerly surface flow is expected to overrun the front and surface trough, which should create areas of widespread training rainfall over Deep South Texas over the next few days.

Rain chances will remain high to very high (80 to 100%) through tomorrow evening before the threat begins to slowly move offshore. Rain chances will decrease to low to moderate (30-60%) tomorrow night into Wednesday but the flooding potential will still persist due to over-saturated soil. A Flood Watch Remains in effect into Thursday morning.

The most likely rainfall amounts between now and Thursday morning will be between 5 to 10 inches, with some isolated areas receiving up to 12 inches. There is ongoing convection which has already caused flooding issues in the middle Rio Grande Valley, with some areas near Weslaco and Progreso already receiving up to 4 to 6 inches this morning. Heavier convection is expected to develop later this evening in the Western Ranchland counties and slowly spread eastward overnight into tomorrow and tomorrow evening. Areas that already received rainfall today will be particularly prone to flash flooding, as the ground is already highly saturated (with some areas still having standing water) in these areas due to this morning's convection.

The National Hurricane Center has also increased the chances of tropical development just off the Texas Coast from 30% to 50% for the next 7 days. Confidence is increasing that inland convection that moves offshore over the next few days could briefly develop into a tropical system as an inland trough moves offshore. There is a 40% chance of formation in the next 48 hours, and a 50% chance of formation over the next 7 days. If this chance materializes, we could see potential development offshore as soon as Wednesday into Thursday, most likely impacting areas to our north and east, but exact impacts and locations are still unknown at this time. This will continue to be monitored.

Heat Risk will be a little less pronouced during ongoing convection tomorrow, though still a bit of a concern. However, Major Heat Risk (level 3 of 4) will be possible on Thursday as the rain begins to move eastward and skies become more sunny. Some areas could reach Heat Advisory criteria as soon as Wednesday afternoon (which will mostly be Moderate, with some small pockets of Major Heat Risk). This Heat Risk concern continues through the weekend, though Thursday appears the be the most impactful day.

A moderate risk of life-threatening rip currents is also expected at area beaches through tomorrow. This could increase later this week, along with beach hazards depending how inland convection behaves once it moves over the Gulf.

AVIATION

(18Z TAFS) Issued at 135 PM CDT Mon Jun 15 2026

Conditions are expected to deteriorate throughout the day as spotty shower and storm development continues. Intermittent VFR to MVFR ceilings are expected throughout the afternoon and early evening before ceilings should stay MVFR by 02-03z and decrease to IFR overnight between 09-12z. Winds should be light to moderate and southeasterly through the entire TAF period with showers giving way to heavier rain by tomorrow morning.

MARINE

Issued at 135 PM CDT Mon Jun 15 2026

Conditions will become increasingly adverse tonight into tomorrow as low presure moves over the area. Small Craft Advisories could be needed tomorrow afternoon, and could be also needed intermittently through Friday as the trough moves offshore, increasing the pressure gradient and wave heights. Conditions could slightly improve for the weekend, but Small Craft Exercise Caution may still be needed through the weekend.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 79 85 77 92 / 70 90 60 40 HARLINGEN 76 83 74 92 / 80 90 60 30 MCALLEN 77 83 77 94 / 100 90 40 20 RIO GRANDE CITY 75 84 74 94 / 90 90 30 10 SOUTH PADRE ISLAND 81 85 80 89 / 70 80 70 40 BAYVIEW/PORT ISABEL 78 85 76 92 / 70 90 70 40

BRO WATCHES/WARNINGS/ADVISORIES

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

GM...None.