DALLAS - Gasoline prices are hitting the accelerator in the aftermath of Hurricane Harvey.

The national average for a gallon of regular gas was $2.54 a gallon as of Friday afternoon, an increase of 18 cents in the last week, according to GasBuddy. In Texas, Ohio, Georgia and the Mid-Atlantic states, prices jumped at least 10 cents a gallon in the last 24 hours, according to AAA.

The U.S. average gas price was already higher than many experts' worst-case forecasts when flooding from the devastating storm began knocking out refineries along the Texas Gulf Coast a week ago.

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Two of the leading price-forecasting analysts, GasBuddy's Patrick DeHaan and Tom Kloza of the Oil Price Information Service, now see the national average rising as high as $2.75 a gallon in the next few days.

Many stations in the Dallas area were out of gas Friday. Those that had some were drawing long lines of drivers even as prices topped $3 a gallon.

Queueing at the pump was largely the result of people rushing out to top off their tanks, not fuel shortages, the analysts emphasized. Interruptions in supply were isolated. DeHaan said only one rack, or wholesale gasoline terminal, out of the six in the Dallas area was dry.

"There is enough gas out there," he said. "It's just a matter of getting it to the right places before motorists panic."

Speaking to the public Friday afternoon, Texas Gov. Greg Abbott said there's "plenty of gasoline in the state of Texas" and that more is being shipped in from surrounding states. A pipeline that had been supplying gasoline from Texas to Oklahoma has been reversed, and fuel was being shipped in from New Mexico and New Orleans, he said at a news conference in Austin.

"Don't worry, we will not run out," Abbott said.

The comments come after widespread reports of gas shortages prompted the head of the Texas agency that regulates the state's oil and gas industry to urge drivers to wait three or four days to fill up their tanks. Texas Railroad Commissioner Ryan Sitton said panic-buying is causing a run on gas and empty fuel pumps.

Long lines could pop up next in states in the East and Southeast, as far north as New York, which get much of their gasoline from the Colonial pipeline that taps into refineries in Texas and Louisiana. The operator shut down the pipeline on Thursday and doesn't expect normal operations to resume until Sunday.

Analysts said some gas from the Northeast is being diverted to Florida and that exports are contributing to the higher prices.

The U.S. now exports large amounts of gas, especially to Mexico and other parts of Latin America, and buyers there are competing with domestic distributors and bidding up prices.

How long the spike in prices lasts will depend on how quickly Gulf Coast refineries are back in business, especially large facilities like Motiva's Port Arthur, Texas, plant and the Exxon Mobil refinery in Baytown, near Houston.

One Chevron station in downtown Dallas that was selling regular for $2.29 a gallon before Harvey bumped up its price to $2.99 on Thursday, and a nearby Shell station was asking $3.97.

QuikTrip, one of the nation's largest convenience store chains, temporarily halted gasoline sales at about half of its 135 stores in the Dallas-Fort Worth area to send the fuel to a few designated stores across the area, said company spokesman Mike Thornbrugh.

Irina Ivanova and Lauren Meltzer contributed reporting.