CHICAGO (CBS) — Though gas prices have been plummeting nationally, drivers in the Chicago area suddenly have seen a major bump at the pump.

Oil prices have reached lows not seen since the Great Recession, and the cost of filling up across the country is way down, so why are Chicago area drivers suddenly paying more?

Patrick DeHaan, senior petroleum analyst at GasBuddy.com, said it’s the result of an outage at the BP refinery in Whiting, Indiana.

“Talking about a plant now that’s running crippled, at less than half of capacity; the largest refinery in the Midwest,” he said.

One gas station owner in Lake County said he’s had to raise prices at the pump by 84 cents per gallon in the past three days, as his costs have surged.

The average price of a gallon of gas in the Chicago area started the day at $2.77, and by late Wednesday morning had risen to $2.87, according to GasBuddy.com. Analysts said it could rise another 20 cents by the end of the day, and 50 to 70 cents per gallon by next week.

DeHaan said the good news is, once the refinery issue is resolved, prices will drop again, with $2 per gallon possible in the fall.

“Once these refinery issues are behind us, once the unit comes back online, a decline will come back to Chicago’s pumps, and we still could be talking about prices in the suburbs at $2 per gallon,” he said.

It’s unknown when the Whiting refinery will be fully operational again, so it’s unclear when prices will go back down.

BP released a statement saying, “On Saturday, Aug. 8, the Whiting Refinery in Indiana shut down the largest of its three crude distillation units for unscheduled repair work. The shutdown was executed without incident and according to protocols.

While the rest of the refinery continues to operate safely, the outage has reduced production.

BP is working to safely restart the unit as soon as possible. In the meantime, the company is working to meet its fuel supply obligations.”