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Another person was confirmed dead following recent heavy rains, bringing the death toll to at least three in Texas this weekend. The latest is a 14-year-old boy whose lifeless body was found in a suburban Dallas storm drain on Monday.

At least 12 people were also reported missing after floodwaters swept homes, cars and people away in parts of Oklahoma and Texas over the weekend. Making the situation worse, a large area of damaging thunderstorms gathered strength in Central Texas on Monday afternoon, sweeping eastward with time toward Dallas and Oklahoma City.

Among the missing are three members of one family in Wimberley, Texas, according to KIII-TV.

See also: Drone video of bridge washed out by floods in Texas

The teen, Damien Blade, had been reported missing by his parents around 10 p.m. Sunday after one of his two dogs showed up to their home muddy and alone. Damien and his other dog were found dead by a police officer and a search dog. They both had apparently drowned.

A man in Milam County, Texas also died Monday. He died in his mobile home after a tornado landed nearby. Authorities have said at least one other person was killed in flooding on Sunday. A Texas high school senior, Alyssa Ramirez, died Saturday night after her car was caught in high water on her way home from prom. The 18-year-old was a cheerleader and homecoming queen at Devine High School, according to My San Antonio.

Texas Governor Greg Abbott declared states of disaster for 24 counties in Texas on Monday morning.

More rain is falling on Monday in some of the areas that were hardest hit by flooding over the weekend, such as the communities of Wimberley and San Marcos, Texas, where the Blanco River transformed from a gentle trickle to raging rapids in a matter of minutes on Sunday. Wimberley is located between San Antonio and Austin.

Here we go again! Tornado Watch until 6pm for the shaded area. Stay alert on this #MemorialDay! #dfwwx #ctxwx pic.twitter.com/ug6VY2ipPs — NWS Fort Worth (@NWSFortWorth) May 25, 2015

The severe thunderstorms that were racing toward Dallas, Tulsa and Oklahoma City on Monday, prompting an array of severe weather alerts, were part of what is known as a mesoscale convective system, arranged on Doppler radar in the shape of an bow from the intense winds that were pushing some of the storms out ahead of others. Such weather systems often feature powerful winds that can damage homes and down power lines.

The Storm Prediction Center in Norman, Oklahoma was predicting a "widespread destructive wind event" across the southern Plains on Monday afternoon into Monday night. With winds gusting near 100 miles per hour, storm complexes such as this one have been responsible for widespread power outages in the past, such as an event that plunged much of the Mid-Atlantic states into darkness for days in June 2012.

People look at one of several destroyed cabins on the banks of the Blanco River in Wimberley, Texas, Sunday May 24, 2015. Flooding in Texas and Oklahoma has led to numerous evacuations.

While the wind may be the big story on Monday, the flooding threat remains high and may last for weeks after historic amounts of water poured down on areas of Texas and Oklahoma that were still mired in a long-lasting drought just three weeks ago. Bulges of water are coursing down major rivers and streams, flooding more areas downstream.

Any new rainfall will only aggravate the flooding that is already occurring.

Hwy 71 has flooded due 2 Dam rupture in park. Please seek higher ground immediately! Water now moving into Tahitian. pic.twitter.com/lsAl7lNYBt — BastropCntyTexas OEM (@BastropCntyOEM) May 26, 2015

The Blanco River rose more than 33 feet in just 3 hours early Sunday morning in Wimberley, Texas, cresting at about 27 feet above flood stage and beating the all-time record crest from 1929 by about 7 feet, before the gauge stopped reporting data.

Lake Travis has picked up nearly 150,000 acre-feet of water in 2 days. Up to 60% capacity right now. #txwx #atxfloods pic.twitter.com/lDl5rIlR0N — Mike Johnson (@wall_cloud) May 26, 2015

After a surge of mud and water flooded their cottage in Wimberley, John and Valerie Nelson fled through waist-deep waters in darkness early Sunday with transformers sparking and trees crashing around them. The single-story house had been carefully rebuilt on stilts so that it would be able to withstand even the worst flooding.

"I'm absolutely dumbfounded," said Valerie Nelson, who has owned the property for about 50 years. "I didn't think the water would ever get that high."

Hundreds of trees along the Blanco were uprooted or snapped, and they collected in piles of debris that soared 20 feet high.

"We've got trees in the rafters," said Cherri Maley, the property manager of a house where the entire rear portion collapsed with the flooding, carrying away furniture.

"We had the refrigerator in a tree," she said. "I think it's a total loss."

.@KETK viewer submission of storm damage in Henderson, Texas. Yes, that's an uprooted tree through a house. #KETKWX pic.twitter.com/Zl53AAc6PY — Reagan Roy (@reaganroy) May 26, 2015

About 1,000 people were evacuated from an area near an earthen dam out of fear that the levee about 50 miles north of Houston could fail. The evacuation order was lifted after weather improved and crews shored up the dam at the Lewis Creek Reservoir. Residents were allowed back to their homes late Sunday.

Dallas faced more severe weather on Monday along with the threat of flooding from the Trinity River, which was expected to crest near 40 feet Monday and lap at the foundations of an industrial park. The Red and Wichita rivers also rose far above flood stage.

In Austin, a local animal shelter had to evacuate 60 dogs due to flooding. The Austin Animal Center, which has been inundated with lost and stray pets following recent storms, expects to be closed for two days.

We are closing for the next 2 days to due to flooding at TLAC. We will still be open for reclaims! http://t.co/R2MXLBdHnd #atxfloods — Austin Animal Center (@austinanimals) May 26, 2015

This May is already the wettest on record for several Plains cities, with days still to go and more rain on the way. So far this year, Oklahoma City has gotten 27.37 inches of rain. It got only 4.29 inches all of last year. Not only is it the wettest May on record there, but it is also the wettest month of any month in that city's history.

The deluges that have descended on the Plains in recent weeks — some accompanied by baseball-sized hail and tornadoes — have formed within a stuck weather regime that has featured a train of moisture moving north from the Gulf of Mexico into the Plains states; here, the moisture has encountered a steady parade of upper-level low-pressure areas and frontal systems moving out of the Southwest and Rockies. These weather systems have provided ample lift to force the warm, moist air to rise, cool and condense, thereby forming clouds and precipitation.

Map showing the tropical connection to the rainfall in the Southern Plains (arrows). Image: NOAA/ESRL

The recent weather pattern has some links to thunderstorm activity and winds in the equatorial tropical Pacific, where an El Niño event is gathering strength. Such events tend to bring wetter-than-average conditions to the southern tier of the U.S. Unfortunately for water-logged residents of Texas and Oklahoma as well as neighboring states, the wet weather pattern shows few signs of changing in the next few weeks.

In addition to El Niño, many climate studies have found that as the world warms in response to rising levels of manmade greenhouse gases, heavy precipitation events are becoming more frequent and intense. This is true in the South Central states, but it's most pronounced in the Northeast and Midwest.

Additional reporting by the Associated Press.