Gas prices are expected to spike 10 to 20 cents a gallon in the next few days after a winter blast knocked out about a dozen refineries in Texas. Regular unleaded gas averaged $2.54 a gallon nationally on Wednesday, up two cents from the previous day, according to AAA. The storm’s also disrupted package deliveries to customers across the country and product shipments to retailers — possibly leading to shortages of some items on shelves. Some experts say prices could creep up to around $3.00 a gallon by summer.