The potential for tropical activity along the lower Texas Gulf Coast has increased slightly compared to earlier today. The National Hurricane Center now gives Invest 98L a 50/50 chance of developing into a tropical depression or a weak tropical storm before making landfall on the Texas-Mexico border tomorrow (Friday evening). Regardless of its classification, the associated hazards are expected to remain largely the same. Heavy rainfall and the risk of localized flooding will be the primary concerns stemming from this system.
There is still considerable uncertainty in this forecast period, as the majority of weather models do not predict any development of this system. However, the overall satellite presentation has improved today. The hurricane hunters conducted a flight through the system this afternoon and found it to be poorly organized, consisting essentially of a cluster of thunderstorms. Nonetheless, very warm waters and a lack of wind shear may promote the chance of it becoming a weak tropical system on Friday as it moves northwest toward the Rio Grande Valley. Even if the system becomes more organized, the threat of significant coastal flooding and damaging winds remains quite low. Dangerous rip currents are likely along the entire Texas Gulf Coast this weekend.
Flash flood outlook for south Texas showing isolated (green) to scattered (yellow) flood risk near coastal areas, with forecast tied to Invest 98L approaching from the Gulf.
Scattered to numerous thunderstorms are expected on Friday across much of the Texas Gulf Coast and into adjacent inland areas. The highest likelihood of numerous showers and possibly heavy rain will be along the lower Texas Gulf Coast and in the Rio Grande Valley. This threat will persist into Friday night and Saturday morning. Storms may produce gusty winds, dangerous cloud-to-ground lightning, and hourly rainfall rates of up to four inches as extremely high moisture levels move inland from the Gulf. The possibility of brief tornadoes cannot be ruled out. Isolated flooding is also a concern, particularly in the Rio Grande Valley, including areas like McAllen and Brownsville.
If the system becomes more organized tomorrow, the threat of heavier rainfall could increase in Deep South Texas in the Rio Grande Valley on Friday night. On Saturday, much of the rainfall will depend on the eventual development of the system. If it does not develop significantly, we may only see scattered showers and storms on Saturday from the Hill Country and Brazos Valley through Southeast Texas and the Golden Triangle. Given the low confidence in this forecast, we encourage everyone to check back for updates tomorrow.