In this case, the moisture is associated with the former Hurricane Norma, the future Hurricane Otis, and a tropical moisture fetch that has ties to what the National Hurricane Center called Tropical Depression 21. Just as Norma broke up crossing Mexico into Texas, Otis, along a more southern route, will also fragment as it tracks from the southern Mexican shoreline of the Pacific Ocean to the Big Bend vicinity of the Rio Grande Valley on Thursday. Additional atmospheric moisture will be added by the southerly fetch that Otis and the “TD 21” remnants are entrained in.
What happens at some point between now and Halloween is that the aforementioned Arctic cold front will slow and link with this moist, unstable air. Otis will add energy and shear, possibly surviving as a mesolow on the slow-to-advance front. Most of the numerical models suggest that the central and eastern thirds of The Lone Star State will have chances for severe weather and (needed) heavy rainfall until the boundary sweeps through on October 30.
And then…colder air progresses to the Gulf an Atlantic coastlines. But only for a few days before the inevitable warm-up.