NHC: Alberto now a tropical depression, heavy rain and flooding continue in South Texas

Millions of people along the southern coast of Texas were under severe weather advisories as officials warned of high storm surge, torrential rain and possible tornadoes as Tropical Storm Alberto barreled over northern Mexico. Here's what we know.

NHC reclassifies Alberto as tropical depression

Tropical Storm Alberto has transitioned into Tropical Depression Alberto, according to the latest update by the National Hurricane Center. The decreased wind speeds characteristic of tropical depressions signal a turning point in the system's aggression.

Read more: What's the difference between a tropical storm and tropical depression?

Alberto brings heavy rainfall, flooding to South Texas

The first named storm in the 2024 Atlantic hurricane season made landfall in Mexico, near the U.S. border, sometime between 4 a.m. and 7 a.m. local time, according to the National Hurricane Center. Along with sustained winds near 45 mph, the storm is forecast to dump up to 20 inches across parts of northeast Mexico with nearly a foot of rain expected throughout southern Texas.

Such high rainfall totals will likely produce "considerable flash flooding and urban flooding" as well as possible mudslides across northern Mexico, the NHC said.

As a tropical depression Alberto's strength is diminishing, though it could still produce life-threatening weather conditions.

Alberto began drenching southern Texas on Wednesday, triggering widespread coastal flooding that left Surfside Beach, a city along the Texas Gulf Coast south of Houston, under several feet of water. The storm also lashed Mexico with heavy rain, and caused the deaths of at least three minors, Nuevo Leon state Governor Samuel Garcia told local media without providing details.

Across southern Texas, the combination of storm surge and high tide is raising alarms on Thursday as floodwaters could reach up to 4 feet along the coast. The deepest waters will breach the shore along the Texas coast just to the north of Mexico, where the surge will be accompanied by large and dangerous waves, according to NHC.

Life-threatening surf and rip current conditions are among the central threats for the Gulf Coast of Texas through Friday. In deep South Texas, multiple counties were under a tornado watch as forecasters warned that a possible tornado or two could spin up through the morning.

All tropical storm watches and warnings have been discontinued all the U.S. Gulf Coast, and heavy rain and gusty winds are beginning to subside for South Texas.

Across the Coastal Bend of Texas, the National Weather Service reported a few gusts of wind above 50 mph and rainfall totals of about 2 to 7 inches.

"Between 4-8 inches of rain can fall across a widespread area from south of Houston to far northeastern Mexico from Monday to Thursday night, while rainfall totals as high as 8-12 inches can occur over South Texas and the higher elevations of northern Mexico," according to AccuWeather.

People are also reading: Storm tracker: See latest details, possible path as tropical storm warning issued in Texas

Alberto makes landfall in Mexico

Tropical Depression Alberto made landfall in Mexico early Thursday morning and began moving farther inland. A tropical storm warning was then issued for a portion of the northeastern Mexico coast.

Here's a quick breakdown of conditions, as of 10 a.m. Thursday:

• Location: about 280 miles southeast of Brownsville, Texas

• Maximum sustained winds: 35 mph

• Movement: west at 18 mph

• Pressure: 999 MB

Governor issues disaster declaration

Texas governor Greg Abbott issued a disaster proclamation for 51 counties Wednesday evening, as winds and flooding from the tropical storm continue hitting the state's coast. He also activated three platoons of the Texas National Guard, including more than 40 personnel, 20 vehicles and Chinook helicopters.

Watches and warnings in Texas

NHC has issued a tropical storm warning for the Texas coast from San Luis Pass southward to the mouth of the Rio Grande. A warning was also issued for the northeastern coast of Mexico south of the mouth of the Rio Grande to Tecolutla.

Track Tropical Depression Alberto

Tropical Depression Alberto becomes first named storm of the season

On Wednesday the NHC named the system in the Gulf, making it the first named storm of the 2024 Atlantic hurricane season.

― USA TODAY reporters Christopher Cann and Cheryl McCloud contributed to this report.

This article originally appeared on Austin American-Statesman: Tropical Depression Alberto 2024: Heavy rains, flooding in Texas