Overnight trading was inconsequential for domestic bond markets with both Treasuries and MBS hitting New York hours very close to 'unchanged.'  Asian market hours saw very slight gains and European hours marked the onset of the selling pressure.  The weakness persisted through 10am, at which point domestic bond markets found their cues to hold ground.

MBS and Treasuries have been doing a lot of 'follow-the-leader' of late, where the leader could be anything from stock prices to German Bund yields to corporate bond issuance.  Indeed part of the more abrupt weakness between 8:30am and 9:00am this morning was in response to the early corporate bond announcements. 

Apart from the supply/demand justification, a more general consideration is the aforementioned "following."  Fresh off the corporate-related selling, Treasuries were also faced with higher stock prices and Bund yields.  Stocks ran into trouble right as they were reaching their near-term technical ceiling (which has been anything near 1990 in the S&P).  We might also keep an eye on the technical ceiling of 0.62 in German Bund yields, which has increasingly been at the scene when Treasuries have managed to bounce back from intraday weakness.  (In this same chart, you can also see the more aggressive pace of selling in Bunds, which likely put additional pressure on US bond markets).