Yanina Wickmayer made the most of a fast start to defeat Yulia Putintseva and book her place in the Citi Open final.
The seventh seed raced out to a 4-0 lead in the first set and never looked back, eventually claiming a 6-4, 6-2 victory in sweltering conditions in Washington.
While Wickmayer surrendered one of her early breaks in the opener, she would see out the set before early inroads in the second cemented her dominant position.
The Belgian will face the unseeded Lauren Davis in what will be her first final of the year.
Davis ended the dream run of wildcard Jessica Pegula who had downed top seed Sam Stosur on Friday after the Australian was forced to retire while trailing.
The 173rd-ranked Pegula couldn't get over the line on Saturday though, with Davis coming out on top 6-2, 6-3.