Discription of Events: Happened yesterday, November 1 2018,on a rainy day at 5.40 pm, near Rudy lane at Windy Hills, Brownsboro Road. As I was driving, this person switched lanes without signaling and came in front of me just less than 5 feet away. I was left with no option rather than bumping at him/her which never happened. Due to heavy rain I was worried of applying breaks but luckily it was at a junction where there was a left lane so I managed to reach the third lane. I escaped narrowly as there was no vehicle in that left lane. Pretty sure there would have been a big crash leading to multi-car collision if the third lane wasnt there. People like them should pay more attention first to put the signal and then give ample time for the vehicle at the rear end to notice and then merge. Extra attention on a wet day. You would have escaped but the person behind you must have had a serious/ fatal accident. Further the chances of my vehicle colliding with vehicles in the opposite side would have been likely then many more lives would have been affected. PLEASE DRIVE CAREFULLY.