The average rate on the 30-year fixed is now 20 basis points higher than it was on Monday and 36 basis points higher than its last low on Sept. 4, according to Mortgage News Daily.

That is the biggest short-term jump since the week following the election of President Donald Trump.

That is the bad news for borrowers. The good news is that rates are still incredibly low, and in the weeks before this turnaround, rates had fallen to the lowest level in three years.

"These sorts of bad performances are most often seen in the wake of stellar performances," said Matthew Graham, chief operating officer of Mortgage News Daily. "August was the best month for mortgage rates, and 2019 has been the best year since 2011. And that's precisely why this terrible week is possible: It's largely a technical correction to the feverish strength in August."

Analysts now wonder if this is a short-term correction from those recent lows or a new shift toward rising rates.

"The big risk here is that the overall rate rally — the one that began in November 2018 — has run its course," said Graham.

If the market "can match 2011's performance, there's a chance rates will move to new all-time lows by the end of the year," he added. But that would require "some legitimate deterioration in the global growth outlook."

Mortgage rates loosely follow the yield of the 10-year Treasury. While moves in the Federal Reserve's rates can affect bond yields, mortgage rates are not necessarily tied to Fed rate cuts or increases. So, even if the Fed cuts rates by a quarter point as is expected next week, that would not necessarily drive mortgage rates down.

While mortgage rates are still historically low, so many borrowers have already refinanced, that the pool of those left who could benefit is extremely rate sensitive.