A savage summer storm that slammed this capital city Thursday night with tornadoes, floods, lightning and hail left at least 12 people dead, more than 30 injured and up to eight reported missing.

The four-hour meteorological frenzy, a once-in-100-years storm, hit downtown Cheyenne with simultaneous fire and flood and washed cars by the dozen down a riverbed that usually lives up to its name: Dry Creek.

Some of the dead and injured had the misfortune to be driving near the creek bed when a wall of water swept them away. Other victims had sought shelter from the tornadoes in their basements and were engulfed by raging flood waters.

Cheyenne resident Peter Pacheco said he fled first to his basement, then raced up two flights of stairs with water rising behind him. When he finally jumped from a second-story window, he landed unhurt in chest-deep hail.

The National Weather Service issued another severe storm warning for the area for this evening but said that the predicted storm would not approach the ferocity of Thursday night's onslaught.

That storm, which stalled over the city, dropped 6.06 inches of rain on Cheyenne in 3 3/4 hours. The average annual rainfall here on the Wyoming plains is 12 inches.

"It was like somebody opened a faucet right above our city and kept it open at ultra-high pressure," said Don Erickson, mayor of this town of 53,000. At the height of the storm, residents said cars, fences, trash trucks, and trees flowed through a residential neighborhood toward the city center.

Jan Jensen used a metaphor echoed by other residents to describe the water pouring into his Cheyenne house: "It looked like they were shooting fire hoses through all our windows."

An early evening rainstorm is an almost daily occurrence here on the eastern fringe of the Rockies, but these nightly rains rarely last more than 15 minutes. The storm here looked normal when it started, just before 7 p.m., but warning sirens blared when a tornado was spotted southwest of town. Devastating hail hammered at cars and smashed the windows of houses and businesses. Lightning started several fires.

The weather service said the storm failed to move away because an unusual thermal inversion held it rigidly over the center of Cheyenne. The mayor said it rained so hard that "you'd sort of expect it to stop after two or three minutes, and it went on three hours."

The confluence of bad weather played havoc with Laramie County's sophisticated disaster alert system.

The 911 emergency lines went out early in the storm. A fire broke out at police headquarters, and when officers moved across the street to the civil defense office they found it had been flooded.

Today, the Union Pacific railyards at the center of town looked more like a harbor than a rail depot. Whole neighborhoods in the northwest section of town took on a wintry face as several inches of hail blanketed the yards.

Erickson said the hail made this the only August day in Cheyenne's history on which the city had to send out snowplows to clear the streets. The stunning force of nature's power was in evidence everywhere. At one street corner, a yellow Pinto had pulled up neatly next to the gas tank at a gas station -- on its roof.

The county coroner was uncertain about the death toll and the causes of the fatalities tonight. Sheriff's deputies said that most of those lost had evidently been swept from their cars by raging water.

There were heroic efforts to save the drivers. Sheriff's deputy Robert Van Alyne swam into Dry Creek and pulled two people from a submerged auto, went back for the third passenger, a girl, 3.

Before he could reach safety, the deputy and the girl were swept away. Their bodies were recovered a mile downstream this morning.

Two victims died of heart attack, the sheriff's office said. One was bailing water from his house, and the other was shoveling hail away from his door.

The storm literally washed out a banquet at a Chinese restaurant. Chairs, tables and patrons were swept out into the street by the wall of water, but there were no fatalities there.

A team of Federal Emergency Management Agency investigators was en route from Denver tonight to determine whether the city qualified for federal disaster assistance.

Contrary to earlier reports, dams on reservoirs west of Cheyenne were not endangered by the storm, the mayor said.

Ironically, the tornado warnings that led some residents to danger in their basements turned out to be unnecessary. The weather service said the nearest tornado touched down several miles outside the city limits