Gasoline prices are continuing their long slide in Vancouver and across the Northwest, AAA Oregon/Idaho reported Tuesday.The average price for regular unleased gasoline in Vancouver was $3.02 per gallon , down from $3.09 a week ago and $3.51 a month ago, AAA reported. And for the fourth consecutive week, Washington and Oregon drivers are enjoying the largest monthly drop in gas prices in the country. Washington’s average gasoline price dropped by 44 cents for the month and 5 cents for the week. The state average is now $3.10 per gallon. Oregon’s average gasoline price dropped by 47 cents for the month and five cents for the week, and is now $3.07 a gallon.The national average for regular unleaded, down four cents for the week, is $2.93 a gallon, AAA said.