10yr yields just moved up to the highest levels of the day (up 2.8bps at 2.256), and Fannie 3.5s are down 6/32nds at 102-29.  This as much as an eighth of a point lower than some rate sheet print times and thus puts some of the early/aggressive lenders in a position to consider negative reprices.

NOTE: there is illiquidity between MBS bid and ask prices again this morning (read this primer to understand the phenomenon).  As such, not every big drop in MBS prices will be truly indicative of the pace of weakness.  If it looks like MBS fell off a small cliff, confirm the drama by looking at Treasuries.  If there's no concurrent spike in Treasuries, you're likely witnessing bid/ask illiquidity in MBS.