Gale-force winds slapped around central Iowa, downing trees, cutting electricity and causing flash flooding on some roadways. The National Weather Service earlier issued a tornado watch for large swaths of Iowa, including Dallas and Polk counties, which continued until midnight.

The storm has headed east, and severe thunderstorm warnings were issued for Johnson and Linn counties. Officials warned of winds of up to 70 mph.

Polk County Emergency Management said police and fire were responded to numerous calls of lightning strkes and roads blocked from downed trees, debris and flash floods.

After a brief lull in the storm earlier this evening, wind and rain returned with a vengeance, and weather forecasters cautioned people not to be fooled: Dangerous weather conditions will continue at least overnight.

KCCI reported winds of up to 67 mph in Des Moines just before it was knocked off the air about 8 p.m. The station returned briefly, before going black again, and reported that downed trees were causing electricity outages, including at its studios. The station returned to air after a short time.

The Des Moines Register is reporting about 17,000 people in central Iowa are without electricity.

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The storm could continue to carry damaging winds and large hail in addition to the possibility of spawning a tornado, the weather service said.

The National Weather Service has issued a flash flood warning for Urbandale, West Des Moines, Windsor Heights and parts of southern Polk and Dallas counties as the result of runoff from heavy rainfall tonight. The warning is in effect until Sunday at 1:30 a.m.

Watch radar images of the storm by clicking here.

A possible tornado damaged a hospital in Creston on Saturday night, according to KCCI.

Authorities with the Creston Police Department said the damage was reported at the  Greater Regional Medical Center about 7:30 p.m., and Creston Mayor Warren Woods said power lines are down and much of the city is without electricity.

Ambulances were transporting patients from the hospital, but there were no reports of serious injuries.

A tornado was briefly spotted by law enforcement officers near Greenfield, the National Weather Service reported.

KCCI-TV and the Des Moines Register are reporting that a tornado likely caused damage to the hospital in Creston in southwest Iowa.

Reports say baseball-sized hail was tearing the siding off homes in northeast Nebraska and that a tornado has touched down in Kansas. Three possible tornadoes were reported in central Oklahoma.

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