From Fed Chair Janet Yellen: The Federal Reserve’s Monetary Policy Toolkit: Past, Present, and Future. Excerpt:

Looking ahead, the FOMC expects moderate growth in real gross domestic product (GDP), additional strengthening in the labor market, and inflation rising to 2 percent over the next few years. Based on this economic outlook, the FOMC continues to anticipate that gradual increases in the federal funds rate will be appropriate over time to achieve and sustain employment and inflation near our statutory objectives. Indeed, in light of the continued solid performance of the labor market and our outlook for economic activity and inflation, I believe the case for an increase in the federal funds rate has strengthened in recent months. Of course, our decisions always depend on the degree to which incoming data continues to confirm the Committee’s outlook.

And, as ever, the economic outlook is uncertain, and so monetary policy is not on a preset course. Our ability to predict how the federal funds rate will evolve over time is quite limited because monetary policy will need to respond to whatever disturbances may buffet the economy. In addition, the level of short-term interest rates consistent with the dual mandate varies over time in response to shifts in underlying economic conditions that are often evident only in hindsight. For these reasons, the range of reasonably likely outcomes for the federal funds rate is quite wide
emphasis added