With the past five sessions having been green for MBS, today affords them the opportunity to do something they haven't done since the end of March 2013.  That was the last time production coupon MBS (the stuff that's most relevant to lender rate sheets at the time) saw 6 consecutive 'up' days, though they came very close just last month.

If there's a good day to attempt such things, today may be it, considering that it's month-end.  That's important because month-end isn't just another time on the calendar for bond markets, but an actual cyclical motivation to make certain trades.  To make a long story short, some trades simply have to be made before the month is out in order for certain portfolios to adhere to published benchmarks. 

If it's easier, think of it like you would children who are required to clean up the toys they were just playing with before moving on to the next activity.  The important thing to know about month-end is that trends can emerge that suggest supply/demand imbalances, and this particularly strong week may be just such a suggestion.  While I've not been above citing geopolitical risk in Ukraine as a contributing factor in this bond market positivity, those sorts of flights-to-safety are typically accompanied by a similar move lower in equities.  This time around, bonds have simply been walking away from equities, and not in much of a flighty fashion:

Banding together in an attempt to overcome (or perhaps to reinforce) the tradeflow-based movement is a fairly substantial set of economic data today.  There's a GDP reading, which is probably a 2nd tier market mover at the moment at 8:30am.  Standing more of a chance to inspire movement is the Chicago PMI report at 9:45am (though keep in mind that markets will start moving at 9:42am if it's a wild one).  Consumer Sentiment and Pending Home Sales round out the morning at 9:55 and 10am respectively, with only the latter having much of a chance to do anything that Chicago PMI isn't already doing.