There has been a good amount of correlation between stock prices and bond yields heading into the end of the month/quarter.  This is not an uncommon occurrence as money managers rebalance portfolios and adjust holdings based on various indices.  This time around, with Monday falling on the end of the month, there has been a good amount of rebalancing activity this week, with much of it coming through yesterday.  It ended up creating a bit of momentum, and momentum can "stop-out" trading positions (meaning that yields fell enough that those who'd been betting on higher yields were forced to 'cover' or buy bonds). 

Today, we're seeing a gravitation back to what we can assume is a more middle-of-the-road month/quarter-end target, somewhere just on the weak side of yesterday's range.  With MBS down only an eighth of a point, the moves aren't severe, but may be enough for negative reprices from a few lenders this morning.

The morning's economic data was generally uneventful, but markets did seem to be waiting for Consumer Sentiment, and the "risk-on" trade (bond yields higher) was waiting to make sure the data didn't come in much lower than forecast.  It didn't.  So risk is on, relatively.  Every bout of selling pressure has been met with decent support so far today though, so the afternoon is still anyone's game.