A tropical wave, or trough of low pressure, has been slowly moving westward across the Gulf Coast since this past weekend. On Monday, the National Hurricane Center outlined a small area of the northern Gulf Coast where they thought there was the chance for tropical development (20%), but as of this morning that chance is now down to zero due to much of the low pressure moving inland into Louisiana today.
Despite this being a weak tropical cyclone, the impacts will be the same: heavy rain and localized flooding. Flash flooding will be a threat across southern Louisiana and southeastern Texas this Tuesday into Tuesday night as some locations receive over 3 inches today and tonight alone.
If you look at the radar loop, you’ll notice a spin to the precipitation thanks to the trough and upper-level low. This spin will allow for rounds of scattered showers and thunderstorms to pivot through southern Mississippi, much of Louisiana, the ArkLaTex, and southeastern Texas today. Since the best moisture supply is over the Gulf of Mexico, the best risk for any heavy downpours will be along the immediate coast.
The trough will continue to trek to the west, bringing the impacts to more of Texas on Wednesday. While occasional, spotty storms remain a risk along the Louisiana coastline, the main activity will become centered over eastern parts of Texas as a potential steady rain, lasting several hours, affects cities like Houston, Corpus Christi, and Austin. This comes after a wet June, so the ground is saturated. If any additional heavy rain occurs, that could trigger some flooding. This flooding will remain very localized, however. In terms of rainfall Wednesday into Wednesday night, some towns will exceed over 3 inches. The best chance for this heavy rain will be between Houston and Beaumont.
By Thursday, the trough will begin to track into Mexico. Before then, however, scattered showers and storms will be possible in the Rio Grande Valley, especially in the morning hours. Conditions will then improve across Texas by the afternoon. Beyond then, the typical hit or miss storms will remain possible across the Gulf Coast states, but the risk for flooding will be lower.
Meanwhile back to the east, we’ll be tracking a second upper-level disturbance, which will move into the Southeast coast on Wednesday, or the Fourth of July. This will bring an enhancement in convection to the Georgia and Carolina coasts Wednesday into Wednesday night. Unlike the diurnal storms when they develop midday and are very hit or miss, these storms will be more organized and a bit more widespread. Thankfully, the day overall will be dry other than the one or two rounds of rain that move in.
This disturbance will then weaken late-week as it also moves west. Again, the typical summertime thunderstorms will remain possible across much of the Southeast. The most widespread of this activity, however, will be along the Gulf Coast.