Today could be viewed at least 2 ways if you're a fan of low rates.  On one hand, you might despair to see that rates are continuing higher after bouncing at the lows of the year last Friday.  On the other hand, you might take some heart in the fact that today's selling was less severe than yesterday's.  Neither approach is necessarily wrong.  

In today's video (for MBS Live members), I discussed in greater detail why we could easily see a bit more selling in the coming days.  Whether or not that selling is already in the process of slowing down remains to be seen.  

As for today's motivation, it's interesting and complex.  Bonds could justify more weakness simply because this is a "correction" the the recent rally, but they received an additional push from a big glut of corporate bond issuance--not to mention the scheduled Treasury issuance over the first 3 days of the week.  

10yr yields tested (and broke, sorta...) above 2.16%--a key technical level in recent weeks.  Holding above tomorrow would imply a showdown with 2.22%.  MBS have taken less damage than Treasuries, with Fannie 3.5 coupons down only 2/32nds as we approach the final trades (it looks like more on charts due to "the roll"--the change over from September to October coupons, where the latter were always trading at slightly lower prices).