The Storm Prediction Center says a dangerous tornado outbreak is likely Saturday in parts of Kansas and Oklahoma as intense storms move into the southern Plains.

Forecasters at the center in Norman, Okla., say there's a high risk of severe weather from Oklahoma City north to Salina, Kan. The severe storms are expected to strike Saturday afternoon and evening.

It is only the second time in U.S. history that the center has issued a high-risk warning more than 24 hours in advance, said Russ Schneider, director of the center, which is part of the National Weather Service. The first such warning was issued in April 2006 before nearly 100 tornadoes tore across a large swathe of the southeastern U.S.

The latest warning was issued as a strong storm system moves in from the western U.S. with cold air combining with low-level moisture coming up from the Gulf region. The difference in wind direction and speed created by the storm system creates instability in the atmosphere that helps create rotation that can spawn tornadoes, said Scott Curl, a meteorologist at the NWS.

They warn that baseball-sized hail could pummel some isolated areas and winds of up to 70 mph are possible. The Storm Prediction Center says Saturday's outbreak could be a ``high-end life threatening event.''

Forecasters say there's a slight risk of severe weather Saturday in the country's midsection, stretching from central Texas northeast to Iowa.

The Storm Prediction Center is part of the National Weather Service.