Mortgage rates shot higher today at their fastest pace of the year today after Fed forecasts suggested members saw the Fed Funds Rate rising sooner and by more than expected.  To be very clear, the Fed Funds Rate is NOT directly tied to mortgage rates, but it can often be the case that expectations of a hike coincide with with mortgage rates moving higher as well.
That was indeed the case today, and the problem was compounded by the fact that markets were surprised by the changes in the forecast.  Instead, the focus had been on how the Fed might evolve the language in its policy statement.  That language did change, but it wasn't outside market expectations by any means.
The surprise in the forecast had to do with 6 Fed members who had previously predicted rates staying the lowest among their peers.  Those 6 members all adjusted their forecasts higher by .25 on average for where they see the Fed Funds Rate at the end of 2015.  There was also a shift in the number of voters preferring a rate hike in 2015 (+1)  vs 2016 (-1). 
Taken together, this was enough of a surprise for financial markets to react somewhat severely in the context of the recent narrow range (it's not severe compared to 2013-style volatility or the bigger picture range in 2014).  Adjusted for changes in closing costs, rates rose an equivalent of 0.10% today for most lenders.  That takes 4.375% out of the running as a prevalently quoted conforming 30yr Fixed rate for the best-qualified borrowers (best-execution) and leaves that honor solely in the hands of 4.5%.