It is widely expected that the FOMC will lower the Fed Funds Rate by at least 0.250%.
When the FOMC lowers the Fed Funds Rate, it is trying to "loosen" credit for American businesses and consumers. When credit is "looser", it is cheaper, and easier to procure.
Looser credit promotes spending and propels the U.S. economy forward.
By contrast, when the FOMC raises the Fed Funds Rate, it is trying to "tighten" credit which, in turn, slows down the U.S. economy.
The FOMC does not control mortgage rates, but it does have a direct impact on Prime Rate because (Prime Rate) = (Fed Funds Rate) + (3.000%).
Credit cards, construction loans and home equity lines of credit are all tied to Prime Rate and so interest rates are expected to fall on these loan types this afternoon.