Mortgage rates are based on mortgage-backed securities (MBS), which are essentially bonds.  Conventional wisdom holds that stocks and bonds supplement one another, and that as "money moves in" to one side of the market, it will move out of the other.  Conventional wisdom is super duper wrong!

If conventional wisdom held true today, we would have seen a very big move lower in rates.  The massive sell-off in stocks means there was a huge amount of cash looking for a new home.  While it's true that some of this cash did find its way into the bond market, the amount doesn't even begin to compare.  By the end of the day, the bonds most closely tied to mortgage rates had barely reentered positive territory. 

Due to the timing of the afternoon market volatility, many mortgage lenders were still showing higher rates compared to yesterday.  Others ended up releasing new rate sheets at the end of the day.  Unfortunately for those on the east coast, many of these reprices happened .

All of the above having been said, tomorrow could be interesting.  If this move in stocks behaves anything like February's example, today may have been a mere warm-up for what's to come.   If stocks continue to drop tomorrow, rates would likely see more benefit.  As far as today goes, the takeaway is that bonds/rates did everything they could to resist improving.  The bigger picture remains challenging.