Big Sell Off After a Nice Rally. Blame The Fed Either Way? Today was one of the rare breed where both stocks and bonds made massive moves without any indisputable, overt, new justification.  It was a gradual, methodical move by intraday standards.  It came on slowly at first, accelerated into the crux of AM liquidity hours, and faded in the afternoon.  While we can point to one or two individual considerations, none of them are up to the task of explaining swings of this size.  It's only when we step back and consider  the entire 24 hours of trading that we can (sort of) frame everything that happened in the context of an initial and secondary reaction to yesterday's Fed announcement and press conference.  Econ Data / Events Fed MBS Buying  10am, 11:30am, 1pm Jobless Claims 200k vs 182k f'cast, 181k prev Market Movement Recap 08:43 AM mixed overnight.  Early modest weakness gave way to a friendly bounce after BOE announcement.  10s and MBS are both just barely stronger. 10:24 AM Quick sell off starting just after 9am and accelerating after the 930am NYSE open.  Corp bond issuance and post-Fed-Day profit taking in play.  Oil's been mentioned, but it just fall back to AM levels with no response in bonds, so...  10yr is up 10bps at 3.046.  4.0 UMBS are down more than half a point. 11:52 AM Another leg of selling and more new long-term highs for yields.  Stocks are tanking too.  10yr up 15bps at 3.096.  MBS down almost 3/4ths of a point. 03:18 PM Losses found support heading into 2pm.  There was a bit of buying after that, but not enough to set anything apart from a sideways tone.  MBS down just under 3/4ths of a point.  10yr up 12bps at 3.066.