textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 1248 PM CDT Fri May 22 2026

Key Messages:

* Isolated showers and thunderstorms could impact the Western Ranchlands this evening as convection fires off the Sierra Madre.

* A Flood Watch is in effect until Monday morning. There is a chance of isolated to scattered flash flooding in areas that receive heavier rainfall on Saturday and Sunday.

* Warm and humid conditions are expected through next weekend with Minor (level 1 of 4) and Moderate (level 2 of 4) Heat Risks expected to impact the area. * A moderate risk of rip currents continues through Saturday afternoon.

DISCUSSION

Issued at 1248 PM CDT Fri May 22 2026

A deeply moist atmospheric profile remains in place throughout the weekend, due to a combination of ample Gulf surface moisture and Pacific moisture aloft, which is being carried into Deep South Texas across Mexico due to persistent westerly 500 mb flow. Resultantly, abnormally high PWAT values (between 1.6 and 2.2 inches) are expected over the region, with the highest values being observed on Saturday. Shortwave activity is also expected over the next few days, which will make the atmosphere unsettled and prone for convection to form. Since the atmospheric profile is so moist, convection that forms this weekend will be persistent and efficient rainmakers, which could result in high precipitation amounts and possibly isolated to scattered flash flooding across portions of Deep South Texas. A Flood Watch is in effect until Monday morning.

The remainder of the afternoon today is expected to be relatively dry and rain free, but convection is expected to form off the Sierra Madres after sunset which could bring a few showers and thunderstorms to the western portion of the CWA during the evening hours. Overall, PoPs are expected to remain relatively low overnight (less then 30 percent), before increasing to 50 to 70 percent tomorrow, as more widespread convection is expected to form with the main shortwave disturbance. The higher PoPs will shift to the eastern counties on Sunday as the main disturbance moves slightly to the east.

The Weather Prediction Center currently has all of Deep South Texas in a Slight Risk (level 2 of 4) for excessive rainfall on Saturday, and the Coastal Counties under a Marginal Risk (level 1 of 4) for Sunday. Current probabilistic guidance for Saturday indicates a 15 to 25% risk that rainfall could exceed flash flood guidance. While areas further north (closer to Corpus and Houston) are expected to receive the heaviest rainfall, given these probabilities, it is therefore possible that Saturday's excessive rainfall risk could trend upward if guidance can agree better on where the areas of heaviest precipitation will occur, or if the heaviest expected rainfall trends more southward.

Most of the rain received this weekend is expected to be beneficial. It is most likely that the majority of areas will receive between 0.5-1.5 inches between now and Monday morning. However, it is possible that some localized areas could receive up to 6 inches where locally heavy rainfall occurs. Areas that will be prone to isolated flash flooding are places where an excess of rain falls over a short period of time (2- 3 inches an hour), or if training showers and storms happen to form, with several showers going over a single area in succession. Right now, the highest precip totals and therefore highest chances of excessive rainfall are expected over the eastern portion of the Northern Ranchlands. However, isolated to scattered flash flooding could still happen anywhere in Deep South Texas and it would be difficult to pinpoint precisely where isolated flash flooding will occur, as shower development will be scattered and random. Therefore, all flood- prone areas should be prepared for the possibility this weekend, despite most areas only expected to actually receive beneficial rain.

Low rain chances continue into Monday as the atmosphere remains somewhat disturbed, with the main chances (20-30%) in the Western Ranchlands as more Sierra Madre convection is expected to form. Conditions dry out Tuesday, but moderate rain chances (30-60%) return for Wednesday and linger (20-30%) for Thursday before becoming dry again for next weekend. Temperatures will remain warm and humid through the next week, with Mild (level 1 of 4) and Moderate (level 2 of 4) Heat Risks throughout the week.

In addition, a moderate risk of life-threatening rip currents are expected to impact area beaches through at least Saturday afternoon.

AVIATION

(18Z TAFS) Issued at 1248 PM CDT Fri May 22 2026

VFR conditions are expected at all airports with light to moderate southeasterly winds. Overcast conditions are expected to develop this evening, and there is a small possibility that MVFR conditions could briefly develop tonight, but confidence was not high enough to include it in the TAF product.

MARINE

Issued at 1248 PM CDT Fri May 22 2026

Favorable conditions are expected this weekend into next week with light to moderate southeasterly winds and low (2 to 4 feet) wave heights. Conditions could briefly deteriorate in the immediate vicinity of any showers and thunderstorms that form offshore, particularly over the weekend.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 79 91 77 90 / 10 50 60 70 HARLINGEN 76 90 74 90 / 10 60 70 70 MCALLEN 77 91 75 91 / 20 70 70 50 RIO GRANDE CITY 75 90 73 91 / 30 50 60 30 SOUTH PADRE ISLAND 80 85 79 84 / 20 40 60 60 BAYVIEW/PORT ISABEL 78 89 76 89 / 10 50 60 70

BRO WATCHES/WARNINGS/ADVISORIES

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

GM...None.