Mortgage rates were unchanged today, despite the potential for volatility surround the Fed's rate announcement.  No one expected the Fed to hike rates at this meeting, but there was a risk they could shake things up via the release of their updated forecasts or during Fed Chair Yellen's press conference.  As it turned out, all of the above was "rate-friendly," at least as far as bond markets are concerned.

Mortgage rates are primarily driven by trading levels in MBS (mortgage-backed-securities), which tend to follow slightly less dramatic versions of the same path seen in US Treasuries--especially the 10yr.  To be sure, today's Fed events were of great benefit to Treasuries, and moderate benefit to MBS, but there are  some caveats by the time we consider actual rates on lender rate sheets.  Reason being, those rates are WORSE, in many cases.  

The biggest caveat is yesterday's market movement.  Bonds were consistently weaker after hitting the best levels in several years in the morning.  But many mortgage lenders held-off raising rates yesterday.  This meant today started at a disadvantage in cases where lenders didn't raise rates yesterday.  Today's best moments just barely made it to yesterday morning's territory, and that was only after the Fed news hit.  

Bottom line: we started out weaker (read: slightly higher rates) versus yesterday and a handful of lenders revised rates lower this afternoon, bringing them back in line with yesterday morning.  If markets don't move overnight, most lenders would be back in line with yesterday morning's levels.