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By Chris Francescani
May 19 (Reuters) - A massive storm front swept north through the central United States on Sunday, hammering the region with fist-sized hail, blinding rain and tornadoes, including a half-mile wide twister that struck near Oklahoma City. News reports said at least one person had died.
By 9:30 p.m. Central Standard Time, more than two dozen tornadoes had been spotted in parts of Iowa, Oklahoma, Kansas and Illinois, according to the National Oceanic and Atmospheric Administration and local news reports. Hail stones, some as large as baseballs, were reported from Georgia to Minnesota, the NOAA said.
Fox News reported that one person was killed in Shawnee, Oklahoma, east of Oklahoma City.
Police in Shawnee could not immediately be reached to confirm the report.
Oklahoma Governor Mary Fallin declared 16 counties of the state disaster areas, according to Jerry Lojka, a spokesman for the state emergency management department.
By late Sunday, power outages were being reported in several Oklahoma counties, according to the Tulsa World newspaper.
Meteorologists had been warning for days that a powerful front was expected to blast through the region, spawning potentially destructive twisters. The extreme weather is expected to continue on Monday, National Weather Service advisories said.
National Weather Service offices across the region issued one urgent warning after another, throughout the afternoon and into the evening.
An extreme weather system stretching from north Texas to Minnesota had been building for hours on Sunday when the day's first tornado touched down near Wichita, Kansas at 3:45 pm Central Standard time, according to a weather service alert.
Just after 6 p.m., the Norman, Oklahoma office posted a Twitter alert on a tornado about to strike Pink, a town on the edge of Oklahoma City.
"Large tornado west of Pink!" the post read. "Take cover RIGHT NOW in Pink! DO NOT WAIT!"
The storm prompted an unusually blunt warning from the central region of the National Weather Service, which covers 14 states.
"You could be killed if not underground or in a tornado shelter," it said. "Complete destruction of neighborhoods, businesses and vehicles will occur. Flying debris will be deadly to people and animals."
Pat Slattery, National Weather Service spokesman for the U.S. Central region, said the advisory was part of a new warning system being tested after a violent tornado that struck Joplin, Missouri on May 22, 2011, killing 158 people and injuring hundreds.
Slattery said the new advisory was reserved for severe tornadoes with the potential to form into "supercell" storms, which produce powerful winds and flash flooding. Supercells are considered to be the most dangerous of four categories of storms because of the extreme weather they generate.
A recent National Oceanic and Atmospheric Administration assessment of the Joplin storm found that "when people heard the first tornado warning, they did not immediately seek shelter. They looked for a secondary source to confirm the tornado," Slattery said. "That got some people killed." (Reporting by Chris Francescani and Ian Simpson; Editing by Theodore d'Afflisio, Richard Chang and David Brunnstrom)