Mortgage rates moved lower today, despite slightly weaker underlying bond markets.  This has been an ongoing phenomenon in recent days.  Bonds improve, implying lower mortgage rates, but lenders wait to drop rates until bond market improvement is vetted.   In the current case, yesterday's market gains remained relatively intact despite today's market losses, thus giving lenders the green light to pass the gains through to mortgage rate sheets.  

Although today's rates aren't appreciably lower than yesterday's, they're technically the best we've seen since June 28th.  More lenders are quoting top tier conventional 30yr fixed rates of 4.0% instead of 4.125%, and some of the aggressive lenders are back down to 3.875%.

If there's been an underlying reason for the hesitation on the part of lenders, the elephant in the room is tomorrow morning's announcement from the European Central Bank (ECB).  Granted, domestic events and monetary policy have a more direct effect on rates in the US, but global bond markets are interconnected.  Any major shock in the EU will be felt in US bond markets, and consequently, mortgage rates.  Some investors are concerned the ECB will allude to plans to taper its bond purchases.  While no official plans are likely to be announced tomorrow, the "clues" offered by ECB President Mario Draghi could cause volatility in rates, for better or worse.