By Mary Wisniewski
CHICAGO, April 13 (Reuters) - Forecasters are warning of a major tornado outbreak in Kansas and Oklahoma this weekend, and Oklahoma got a first taste of it on Friday as a twister touched down near the National Weather Service office in Norman.
A tornado was seen near the University of Oklahoma campus in Norman just after 4 p.m. local time - the same town that holds the National Storm Prediction Center, according to a Twitter post from Rick Smith, a National Weather Service meteorologist.
The Norman tornado ripped roofs from buildings, downed power lines and uprooted trees across Norman, a town of 110,000 people 20 miles (32 km) south of Oklahoma City, television images showed. City Hall was among the structures damaged, said Keli Cain, a spokeswoman for the Oklahoma Department of Emergency Management
An operator at the University of Oklahoma said people had been warned to get to a basement or low floor.
"I was watching this tornado on TV, which was neat until I realized it was right here in Norman," said the operator, who did not give a name.
Atmospheric conditions for the weekend will be similar to those that caused severe storms in parts of the Midwest and Southeast in early March that killed more than 50 people, said Steve Weiss, science support branch chief for the National Storm Prediction Center.
"We see potentially some ... very damaging tornadoes," Weiss said.
Oklahoma is already having severe weather Friday, and a twister was also reported in Copperton in the state's southwest corner. Tornado warnings were issued for two counties, Comanche and Kiowa.
But the biggest storms were expected on Saturday, said Weiss, who was watching heavy rain out of his office window in Norman on Friday afternoon. "It's not unusual to have successive days," he said.
Conditions favor strong thunderstorms in Kansas and Oklahoma on Saturday, with a few "supercell" storms with rotating updrafts, Weiss said.
"The potential is that some of the supercells could be long-lived, so if they produce tornadoes they could be on the ground for a while," he said.
STORMS MAY CONTINUE SATURDAY AFTER DARK
Forecasters said the storms could start in earnest Saturday afternoon into the early evening and continue after dark, and Oklahoma activated its emergency operations center in anticipation of the storms.
"The really dangerous part is that it looks like it's going to be overnight," said Kurt Van Speybroeck, emergency response meteorologist for the National Weather Service. "It's a really bad combination to get tornadoes at night because they're harder to see. It could be a really bad evening."
Storms could strike heavily populated areas such as Oklahoma City, and Wichita and Topeka, Kansas, Weiss said.
The high-risk area is from about the I-40 highway in Oklahoma City going north along I-35 to I-70 in central Kansas, said Van Speybroeck.
Northwest Texas into Nebraska and parts of Iowa and Missouri are also at risk for thunderstorms and tornadoes this weekend. Southwest Wisconsin has a slight risk of tornadoes for Saturday into Sunday, with a chance for thunderstorms, hail and tornadoes for the whole state Sunday, Van Speybroeck said.
The storm warnings have led to the rescheduling of the Rotary Club "Beer Sprocket" fundraiser Saturday in Choctaw, near Oklahoma City. The outdoor event attracts about 600 people.
"The last thing I want to do is put the revelers for this event in harm's way, as well as the staffers and vendors," organizer Mike Turek said.
Van Speybroeck said the large number of tornadoes was linked to warm, moist air off the Gulf of Mexico, which brings energy for severe storms.
"When the cooler air starts to move out of the west and across the region that causes an increase in instability," he said. "It has been a pretty vigorous spring."
He predicted a gradual slowdown in these storm systems as summer approaches.
The U.S. tornado season started early this year. Tornadoes have been blamed for 57 deaths so far in 2012 in the Midwest and South, raising concerns that this year would be a repeat of 2011, the deadliest tornado year in nearly a century.
In 2011 there were 550 tornado deaths, including 316 people on April 27 in five Southern states, and 161 people in Joplin, Missouri, on May 22.
Insurers have already lost as much as $2.5 billion during the 2012 tornado season, mostly from a record March 2 outbreak. That follows record-breaking losses of $26 billion during the 2011 tornado season. (Additional reporting by Ben Berkowitz, Andrew Stern, and Steve Olafson in Oklahoma City; Editing by Xavier Briand and Eric Beech)
04/13/2012 10:06 PM EDT
Minor Injuries Reported In Norman
@ AntDeRosa :
RT @stormchaser4850: Update: Norman, OK Regional Hospital is reporting 11 people with minor injuries due to the earlier tornado via @OKCFOX
04/13/2012 10:05 PM EDT
Thousands Without Power
@ BreakingNews :
04/13/2012 7:18 PM EDT
Likely Tornado Near Blair
@ wunderground :
A tornado is likely on the ground near Blair in Jackson County, OK. Take cover now!
04/13/2012 6:15 PM EDT
Oklahoma City Area Clearing Up
@ USWeatherExpert :
Storm over. OKC metro. We are headed to NW OK for evening development http://t.co/zPiDUO0N
04/13/2012 6:12 PM EDT
Report On The Ground
Per HuffPost commenter PurpleTomato:
“I've lived in Oklahoma most of my 58 years and this is the first time i've been in a tornado.I watched as electric poles broke in half next to my vehicle and dropped hot lines at eye level right in my path at the intersection of Lindsay and 24th in Norman just north of Highway 9.It was quite an interesting drive home.I saw a lot of damage."
04/13/2012 6:07 PM EDT
New Warning Issued
@ Ala_StormChaser :
New Warning OUN issues Tornado Warning for Pottawatomie [OK] till 5:30 PM CDT #okwx
04/13/2012 6:03 PM EDT
The National Weather Service has issued warnings for parts of Oklahoma. At 4:46 p.m. Central Time, meteorologists detected "a severe thunderstorm capable of producing half dollar size hail and damaging winds in excess of 60MPH." They advise people in the area to move inside a sturdy building until the storm has passed.
04/13/2012 5:57 PM EDT
Storm Damage From Helicopter
KFOR chopper shows tornado damage in Norman, OK (via @weatherchannel)
04/13/2012 5:56 PM EDT
'Just Survived A Tornado'
Twitter user @OhJenTucker of Norman, Oklahoma posted this tweet with a photo from her iPhone following the storm.
@ OhJenTucker :
Just survived a tornado hitting our house http://t.co/8cXrVNGs
04/13/2012 5:53 PM EDT
Severe Weather Warning Issued
@ altusem :
OUN issues Severe Thunderstorm Warning for Greer, Harmon, Jackson [OK] till 5:45 PM CDT #AltusOK #okwx