Powell's 15-year reign as England boss came to an end on Tuesday following a disappointing showing at Euro 2013, where her side - finalists four years ago - finished bottom of their group.
The FA now has only four weeks to find a new manager ahead of a fresh qualification campaign for the 2015 World Cup that starts with home games against Belarus on 21 September and Turkey five days later.
Canada's English coach John Herdman is among the favourites to succeed Powell but Horne revealed a new head of performance will tasked with ensuring emerging talent can break through at the top level.
"We just decided there was a need for a fresh outlook," Horne told Sky Sports News.
"We've got two appointments we'll look to make now: a women's senior coach, with a focus just on running that team and working with those semi-professional athletes, but also a head of women's performance to make sure we're managing that talent pathway.
"So it's two new roles we'll look to recruit."
FA chairman Greg Dyke insisted the move to disperse with Powell's services was the right one.
"Hope's done a great job for women's football in this country and how it's developed over 15 years is important but every so often you do need a change," Dyke said.
"There's a period in which you're most effective and over time you become less effective and I think that was the decision."
Powell's former counterpart Roy Hodgson echoed Dyke's sentiments but credited the work she had done during her time in charge.
"Hope has done a good job for women's football in this country," he said.
"If you look at what's happened over 15 years it's enormous, the change. But every so often you have to make changes."