WRAPUP 1-Storm hobbles Alberta refineries, cuts fuel supply

* Power outages hit Petro-Canada, Imperial refineries

* Petro-Canada gasoline unit suffers damage

* Outages worsen already-tight supply situation

CALGARY, Alberta, July 21 (Reuters) - A severe weekend storm in the Edmonton, Alberta, area knocked out power to two of the region's three major refineries, worsening an already-tight gasoline supply situation, industry officials said on Tuesday.

Worst hit in the wind, hail and electrical storm was Petro-Canada's PCA.TO 135,000 barrel a day refinery. Its major gasoline processing unit suffered damage when the plant was knocked off line, spokesman Jon Hamilton said.

Petro-Canada has been forced to temporarily ration fuel supplies to its retail and wholesale outlets and its associates, he said.

Imperial Oil Ltd's (IMO.TO) 187,000 barrel a day refinery also suffered a power outage and is slowly ramping back up in a process that will take days, the company said.

With winds topping 100 km (62 miles) per hour, the storm late on Saturday downed hundreds of trees, damaged buildings and left thousands of residents without electricity in Alberta's capital city.

Petro-Canada does not currently classify the damage to its processing unit, called a catalytic cracker, as severe, but Hamilton said he did not know how long repairs will take.

"Diesel is OK from a supply perspective, but even when we have all the other units up, our capacity to produce gasoline will be limited at best," Hamilton said. "And the situation with gasoline was tight in Alberta going into the storm."

The company is making arrangements to get additional petroleum products shipped into the area while it fixes the damage and while it and Imperial go through the slow return to normal production rates.

"It's in restart," Imperial spokesman Jon Harding said of his company's plant. "And that will take several days because it was like a 'hard park'," Harding said.

The other refinery in the region, Royal Dutch Shell's (RDSa.L) 98,000 barrel a day Scotford plant, was said to have not suffered a power outage. (Reporting by Jeffrey Jones; editing by Peter Galloway)