10yr yields hit the highest levels in more than 4 years this afternoon as bigger-picture selling pressure looks to be taking the reigns back from the Springtime consolidation that helped rates hold steady-to-slightly lower in March. 

There are no big, obvious reasons for the sudden spike in rates. We're left to cobble together a narrative from boring, esoteric stuff like an "imbalance in trading positions," anxiety over the data, earnings, and bond supply next week, and the end of a few days of extra help from tax deadline retirement account funding.

Or, if you'd like to go with fewer words, it's no less valid to say that technicals and momentum are the culprits.

In other words, bonds were in a consolidation trend. They tested the ceiling, broke the ceiling, and have been selling aggressively since then. That selling begets more selling as it forces anyone holding long positions to liquidate (i.e. they have to sell bonds as their stop-loss levels are hit, and their selling pushes yields that much higher, potentially above other traders' stop-loss levels).

Long story short, if the longer-term selling trend is bonds' big bad wolf, he'd been knocking over the past few days with today bringing that telltale huffing and puffing. We'll see what our house is made of next week.