Rates on Zillow Mortgage Marketplace are shooting downward today — 30-year fixed purchase mortgages are at 4.82% as I write –  thanks to The Federal Reserve announcing today that they will spend up to $300 billion over the next six months to buy mortgage-backed securities. The goal is to lower rates on mortgage and other consumer debt.

They also announced that they will buy more mortgage-back securities guaranteed by Freddie and Fannie. Not only do some believe that this will keep rates at rock-bottom levels, others predict a rate free fall for the next few days.

The drop in mortgage rates has been dramatic for the past hour. Prior to the announcement, the national rate for purchase mortgages was about 5.32%. As of 3 p.m. Pacific time rates had plunged to 4.82%. Let’s hope this rally continues!

Here’s the chart for the past month — check out current mortgage rates on Zillow Mortgage Marketplace.