Keeping an eye on the 6 month yield count. If it can break resistance, it may accelerate and catch all the talking heads off guard of course. If short term yields rise (and particularly rapidly) what will this do to the Fed's balance sheet? Their massive leverage will break rather easily if one can imagine.
In my opinion, this resistance line is the only thing keeping the Fed's neck above treading water. It is no coincidence that the resistance line runs back toward when they started really ramping up the first QE. Resistance breaks, and the Fed's balance sheet will break.