JPMorgan Chase & Co. has some advice for regional banks: A deposit drain is coming, so merge while you can.

The company's investment bankers are warning depository clients that they may begin feeling the crunch in December, thanks to a byproduct of how the U.S. Federal Reserve propped up the economy after the financial crisis, according to a copy of a confidential presentation obtained by Bloomberg News and confirmed by a JPMorgan spokesman.

JPMorgan argues that some midsize U.S. banks — those with $50 billion in assets or less — could face a funding problem in coming years as the Fed goes about shrinking its massive balance sheet, according to the 19-page report the New York-based bank has begun sharing with clients.