Same-store retail sales from many of the country’s largest chains are scheduled to hit the tape tomorrow. Sales in March and April rose just 1.4% and 3%, respectively, so the most recent projection from Retail Metrics that sales will rise 2.8% represents a bit of a disappointment. In May of 2012, same-store sales rose 2%.

Walgreen Co. (NYSE: WAG) reported May sales yesterday, and posted a gain of 2.8%. Costco Wholesale Corp. (NASDAQ: COST), Gap Inc. (NYSE: GPS), and Buckle Inc. (NYSE: BKE) are projected to post a year-over-year May sales gain of more than 3%, but Rite Aid Corp. (NYSE: RAD) is expected to post a decline of 1.9%, primarily on poor pharmacy sales.

J.C. Penney Co. Inc. (NYSE: JCP) drags the department store group down with a projected drop in same-store sales of 6.6%. Sears Holdings Corp. (NASDAQ: SHLD) is forecast to see sales drop 3.5% in May.

Among the discount stores, Costco is expected to post a gain of 4.4% excluding gasoline sales and PriceSmart Inc. (NASDAQ: PSMT) is forecast to show a gain of 8.2%. Stein Mart Inc. (NASDAQ: SMRT) is expected to post a 3.7% jump in same-store sales for May.

Wal-Mart Stores Inc. (NYSE: WMT) is among the many stores that no longer report monthly sales, but Retail Metrics forecasts sales at Sam’s Club stores will rise by 2.4% while sales at the company’s other stores will rise by 1%. Overall, Walmart sales are forecast to rise 1.2%, well below last year’s 3% gain in May.

Retail Metrics notes that improving weather, rising stock prices, better news on housing, and rising consumer confidence should have contributed to higher spending in May. The less-than-stirring forecast has been hampered by higher gasoline prices and stagnant personal income.