Steamboat Springs City Council is holding a special meeting at 10 a.m. this Friday, Aug. 21, to formally discuss a potential ballot measure this fall that would ask voters in Steamboat — and virtually all other Yampa Valley municipalities — to pay a 0.5% sales tax to fund the Yampa Valley Regional Transportation Authority. The decision to hold the meeting was made after the RTA board’s regular meeting on Monday, Aug. 17, where board members rev…