The Storm Prediction Center (or SPC) is the branch of the National Weather Service (NWS) charged with issuing timely and accurate forecasts pertaining to severe thunderstorms, tornadoes and other small scale severe weather phenomena.
While severe thunderstorms and tornadoes are the most common things that come to mind when we talk about the SPC, they also provide forecasts and other guidance concerning severe winter weather hazards, heavy rainfall and flash flooding, and even fire weather hazards.
For most of the last 50 years the unit was housed in the Federal Building in Kansas City, MO. In 1997 the unit was moved to Norman, OK and was housed inside the National Severe Storms Laboratory. Its most recent move in September 2006 was to the brand new, state of the art National Weather Center building on the University of Oklahoma campus (shown in the image above).
The official website is located here.