See Gertrude Chavez-Dreyfuss, "Fed's Bullard says U.S. yield curve might invert by early 2019," Reuters, May 15, 2018, https://www.reuters.com/article/usa-fed-bullard-yieldcurve/update-1-feds-bullard-says-us -yield-curve-might-invert-by-early-2019-idUSL2N1SL10U. This, naturally, is not certain to happen, but has happened before.
9  overnight call rate of around 0.25 percent set as the guideline for money market operations), on July 14, 2006 (termination of zero interest rates; policy rate hike from 0 percent to around 0.25 percent), and on February 21, 2007 (policy rate hike from around 0.25 percent to around 0.5 percent), the yield curve flattened, that is, the term spread declined.