Mortgage rates moved just a bit lower today, bringing them to their best levels in exactly 1 week.  Most borrowers will see little-to-no difference between yesterday and today's loan quotes with the exception, perhaps, of a modest reduction in upfront costs.  That means 4.25% remains intact as the most prevalent conventional 30yr fixed rate on top tier scenarios. 

Bond markets (and thus, rates) responded favorably today to a series of weaker economic reports.  In general, weaker economic data tends to help bonds and hurt stocks.  Some of the positivity was also motivated by the calendar as certain traders are required to hold a certain mix of bonds by the end of any given month.  In other words, some investors were buying bonds because they wanted to and other were buying because they had to.

From here, the potential for volatility increases as data and events get even more serious through the end of the week.  There are several important reports tomorrow as well as an updated policy statement from the Fed.  Although there's essentially no chance that the Fed will hike rates at this meeting, investors will nonetheless look for clues about the Fed's thinking based on subtle changes in the text of the statement.