(USA TODAY) It's been a roller coaster year for gas prices, which began the year averaging $3.29 a gallon, then zoomed to $3.78 in February before dropping to $3.50 last month. Current average price: $3.60. Troubles at several oil refineries are driving gasoline prices sharply higher in the Midwest, and the regional shortages are expected to boost pump prices nationwide. While the USA may be dripping in new found crude oil deposits and early May supplies were at their highest levels since the early 1930s, issues at a handful of refineries that turn crude into gasoline and diesel fuel underscore how kinks in the supply chain can cause quick surges in what consumers pay at the pump. Gas prices in Minnesota, Iowa, Missouri, North Dakota, South Dakota, Nebraska, Ohio, Oklahoma and Wisconsin have spiked up to 27 cents a gallon the past week alone. Behind the rise: outages and extended maintenance has curbed output at refineries in Joliet, Ill., Whiting, Ind; Tulsa, Okla, and Eldorado, Kansas. In Minnesota, regular, unleaded gas now averages $3.99 a gallon -- an all-time state record. With some Twin Cities outlets now selling gas for more than $4.20 a gallon, Patrick DeHaan, senior analyst for price tracker gasbuddy.com, expects Minnesota to average the priciest gasoline in the continental U.S., overtaking California, which now averages $4.06 a gallon. "It's amazing what problems refinery issues can cause,'' says DeHaan. "If another refinery went down, all hell would break loose." Nationally, prices average $3.60 a gallon after beginning 2013 at $3.29. Some industry observers thought this year's prices had peaked at $3.78 in February after sliding to $3.50 April 29. But the Midwest's refinery issues are now expected to keep propel prices for several weeks, perhaps to $3.85 a gallon nationwide.