Jessica Lerner

There will be "choppiness in the municipal bond market through the end of the year," said Anders S. Persson, Nuveen's chief investment officer for Global Fixed Income, and Daniel J. Close, Nuveen's head of municipals.

The Bloomberg Municipal Index and High-Yield Index lost 3.3% and 3.9%, respectively, in September.

September's total volume ticked up 1.2% to $27.585 billion in 531 issues from $27.251 billion in 592 issues a year earlier. However, the month's total is lower than the $30.652 billion 10-year average, according to Refinitiv data.

The last time muni mutual funds saw outflows top $1 billion was the week ending May 31 when they were $1.345 billion.

"The market has taken to heart the [Federal Open Market Committee] actions from last week," said Jeff Lipton, managing director of credit research at Oppenheimer Inc.

Yields have "risen substantially over the last week as the market seeks to find at least a minor level of balance or equilibrium," said Tom Kozlik, managing director and head of public policy and municipal strategy at HilltopSecurities.

Data for the second quarter show the face amount of munis outstanding rose 0.4% quarter-over-quarter, or $15.5 billion, to $4.043 trillion.

The Texas Water Development Board leads the new-issue calendar with $1 billion of revenue bonds.

The general bias toward muni rates is that they would be a bit higher with technicals "being a little less supportive than they were in August, plus what we heard with from the Fed 'higher for longer,' and potentially another hike," said Jeff MacDonald, head of Fixed Income Strategies at Fiduciary Trust International.

As was expected, the FOMC held rates in a range between 5.25% and 5.50%, but the dot plot in the Summary of Economic Projections showed 12 of 19 members expect another 25-basis-point rate hike this year.