Mapping the Market: Treasury yields flirt with a breakout that could turn into much more

For now, a quick retreat back below 4.52% and then 4.44% would raise doubts about a breakout to higher yields. But as long as yields hold above 4.29% or so, the bullish case stays intact, with a break below that level opening the door to 4.04%-3.92%. On the upside, clearing 4.6358% could pave the way toward 4.687%, then 4.81% and even 5%.

• Yields are testing the top of a long-term triangle pattern near 4.56%
• A rare, decades-long stretch of "quiet" trading often precedes a big move
• Key levels to watch: support at 4.52%/4.44% then 4.29%, resistance at 4.687%, 4.81% and 5%

What may intrigue market participants more is a separate signal pointing to unusually calm trading conditions. A measure known as Bollinger BandWidth, which tracks how compressed or stretched a market's volatility has become, shows monthly readings hit their lowest level since 1989 at the end of May. Such quiet spells do not reveal which way a market will break, but they have often preceded sharp moves once they end.