U.S. drivers should expect to see a modest further increase in gasoline prices as refinery outages cut supply and plants begin making more expensive summer-grade fuels, according to a new government report.

Retail gasoline, already at a record level for this time of year, hasnt yet caught up with a steep rise in wholesale prices in 2013, the Energy Information Administration, the Energy Departments statistical arm, said on its website late Thursday.

Gasoline at the pump has climbed 45 cents a gallon since the beginning of the year, the agency said.

Despite the significant rise in retail gasoline prices since the start of the year, a part of the even steeper rise in wholesale prices has not been fully reflected in pump prices, the agency said in its This Week in Petroleum report.

Scheduled and unplanned refinery shutdowns across the country, coupled with the seasonal switch in fuel specifications, triggered a surge in wholesale prices.

Plant shutdowns on the West Coast have been particularly heavy, with more than 300,000 barrels a day of fluid catalytic cracking capacity offline at one point in January, the agency said.

While some capacity has come back online, several outages persist in the region, the EIA said.

Even as refineries restore production over the next several weeks, new supplies will be countered by a typical increase in demand at the beginning of spring and short-term gasoline prices will remain volatile and sensitive to unplanned outages, the EIA said.

Retail gasoline prices averaged $3.65 a gallon, up 18 cents in the past week on the Missouri side of the St. Louis area, according to AAA Fuel Gauge Report on Friday. Theyre up 20 cents, to $3.85, in the Metro East.