MBS have added another tick (0.03) to the day's previous highs as bonds rally in the afternoon.  The passing of the week's Treasury supply is one major consideration, but even then, Treasuries have been rallying all day.  The rally began right at the 8:20am CME open suggesting domestic traders set out with the intention of buying today. 

That said, the afternoon is seeing some extra love as corporate bond hedges are being bought back.  (what does that mean?).  10s now down more than 6bps at .603. 2.5 UMBS up 6 ticks on the day at 104-03 (+.19 at 104.09).