Across South Central, Central, Eastern & Northeastern TX: There will be a lot of heavy rain and other effects in southeast, eastern, and central Texas because of an interesting trend. In the south, where the moisture is deeper in the air, this will increase the chance of floods and make it harder to get around. At the same time, there will be convective action with showers all over the area. There is more information about the weather and the area below.
Forecast as a Whole: A trough with a negative tilt is expected to move eastward across the south-central U.S. This will bring very heavy Gulf moisture to parts of northeastern Texas, the east coast, and the central and eastern parts of Texas. On Sunday morning, dew points will start to rise significantly. By Monday evening, they should hit the mid to possibly high 60s, which is more than enough.
Since the lift is happening, it will be mostly cloudy across the region on Sunday before it starts to rain heavily. This, along with a low-level jet steering the system and letting a southwest flow get stronger in the air, will make it possible for it to rain very heavily. This makes floods more likely all over the area, but especially in south-central Texas.
Across TX Timing & Impact: Around Sunday afternoon, rain will start to fall in central, southern, south-central, eastern, and northeastern Texas. They will cover more ground starting in the west and going northeast across the area. Then, as more moisture moves into the area, heavy rain with thunderstorms will first hit southern Texas from Sunday night into Monday morning. It will cover a larger area as it moves through the rest of the region.
It looks like the places around Houston and the southern and central parts of Texas are getting the most heavy rain. The heavy rain will keep coming down, but by Monday night, it will be spread out more. Then, on Tuesday, another strong pulse will come through, bringing more moderate to heavy rain to the area, this time mostly in eastern Texas. Any leftover moisture will lead to more scattered showers through Wednesday. After that, the moisture and impulses will move east into the southeastern U.S.