Mortgage rates moved slightly lower today despite moderate weakness in the bond market.  Typically, bond weakness results in rates moving higher, all other things being equal.  The most common reason for these sorts of discrepancies can be summed up with one simple word: TIMING.  

The bond market moves throughout the day.  Mortgage lenders, however, prefer to adjust rates only one time each morning, although they will issue mid-day reprices if the bond market is volatile enough.  In yesterday's case, bonds improved throughout the day, but not enough for the average lender to issue a mid-day reprice.  Even then, lenders don't tend to pass along all of the improvement implied by bond market gains all at once.  

Bottom line: lenders were still getting caught up with yesterday's bond market strength by the time they needed to issue today's first rates sheets.  Incidentally, the shoe is now on the other foot.  Bonds lost enough ground this afternoon to suggest mortgage rates should be back in line with yesterday's levels.  If bonds don't change much overnight, it wouldn't be a surprise to see the average lender move slightly higher in rate by tomorrow morning.