It's not normal for a 5yr Treasury auction to cause the biggest move in any given day for bond markets.  That's an honor typically reserved for 10yr auctions and even those are hit and miss.  To be fair, today's 5yr auction definitely didn't cause a major reaction.  It was simply the only quasi-relevant event on the calendar of scheduled events.  Unscheduled events were dominated by coverage of Hurricane Harvey.

All of the above transpired against the backdrop of the very light trading activity that exemplifies summertime Mondays.  In that environment, it's easier than normal for any given event or any given piece of economic data to have an outsized impact.

Caveats aside, should we be interested in the fact that yields broke below 2.16%?  After all, that's an important technical level that we've been watching from afar since April and more closely over the past 2 weeks.  That's a tough call at the moment for a few reasons.  First and foremost, early overnight trading promises to be volatile with North Korea launching a missile over Japanese air space.  Secondly, today's trading didn't really "confirm" the break of 2.16% (domestic trading leveled off at 2.159).  Bottom line, we'll need to see how tomorrow goes before making a case for technical confirmation.