Flash Flooding Across the South

Heavy rain that caused major flash flooding across parts of Texas continues to move east across the Gulf Coast and Southeast states. As it moves out of areas soaked by remnants of Hurricane Patricia a week ago and into areas where the soil is drier, the flood threat will diminish somewhat.

As much as 13 inches of rain in upper coastal Texas spawned major flash flooding across Houston and nearby communities Saturday. Flash floods in central and southeast Texas have killed at least four people since Friday and closed countless roads and flooded homes.

(MORE: Latest on Deadly Flooding in South)

Gulf Moisture Feeds Heavy Rain Threat

A plume of moisture feed a storm system over the Deep South with a slow-moving frontal boundary as the focus for much of the rain.

With bands of rain and thunderstorms streaming along the front, some areas near the front picked up locally heavy rainfall.

Through Monday night, the flow of moisture continued as the frontal boundary slide east across Florida, Georgia and the Carolinas. 

Aside from the heavy rain and flash flooding threats, there was also a few isolated severe thunderstorms, thanks in part to some modest instability and favorable low level wind fields.

Flooding and Rainfall Reports

The official daily rainfall total on Friday for Austin Bergstrom International Airport (ABIA) was 14.99 inches, according to the San Antonio National Weather Service office. This shattered the all-time daily rainfall record for the Bergstrom site, including its years as Bergstrom Air Force Base, since it began keeping weather records in 1942. The previous one-day record at Bergstrom was 8.70 inches on Nov. 23, 1974.

Friday's rainfall was also greater than any previous 15-day period on record for the airport site. Combined with rains from the Oct. 22-25 storm and additional rainfall Saturday, ABIA picked up 23.82 inches of rain in the last 10 days of October.

As only a trace of rain had fallen in October prior to the 22nd, the monthly total for October 2015 is also 23.82 inches, establishing a new all-time record rainfall for any month at Bergstrom. The previous record was 15.59 inches in June 1981.

The total at ABIA narrowly missed tying the wettest calendar day at any observation site in the city's history. That occurred when 15.00 inches fell in downtown Austin on September 9, 1921.

The Lower Colorado River Authority (LCRA) gauge along Onion Creek at U.S. 183, very close to ABIA, recorded 13.40 inches of rain in just 3 hours Friday morning.

Onion Creek subsequently climbed to a crest of 39.12 feet, which is more than 22 feet above flood stage and second only to its all-time crest of 40.2 feet set on Halloween in 2013. The two crests, almost exactly two years apart, are the only two that outrank the September 1921 flood at this gauge, whose records date back at least 146 years.

Upstream, Onion Creek shattered its previous record crest at Driftwood of 25.1 feet during the devastating flash floods of Oct. 17, 1998.

Other rainfall and river gauge reports included:

• Houston: Hobby Airport set a daily rainfall record Saturday with 5.30 inches of rain. Parts of Harris County saw more than 12 inches of rain.
• Lake Mexia, Texas: Lake levels rose to 4 feet above normal pool, prompting evacuations of some residents near the lake.
• Brownsville, Texas: 4.71 inches of rain in roughly 1 hour and 45 minutes through 12:39 p.m. CDT Friday.
• San Marcos, Texas: The Blanco River rose 34 feet from Friday morning to the afternoon, cresting just under one-half a foot lower than its destructive Memorial Day flood crest.
• Wimberley, Texas: The Blanco River crested just over 13.5 feet above flood stage just before midday Friday, nearly matching the Halloween 2013 crest, but over 18 feet lower than the historic May flood event.

MORE ON WEATHER.COM: Texas Flooding, Damage (PHOTOS)