U.S. sales receipts dropped slightly week-to-week in the period ending Saturday, a national trade group said Tuesday. The International Council of Shopping Centers said sales dropped 0.1 percent in the week, but rose 2.8 percent compared to the same week of 2010. \"The pace of shopper footfall was weaker for the period, especially at discounters and department stores,\" ICSC said. The report said warm weather may have slowed enthusiasm for a fall lineup of products. Weather Trends International said the temperature averaged 1.4 degrees Fahrenheit warmer than the same week a year earlier. That said, shopping in the first part of the week was hampered by heavy rain and snowfall in Western states. \"This likely spurred outerwear sales in the West,\" ICSC said. However, on the East Coast, Weather Trends International said, \"the week started on the cool side, but warmed appreciably as the week progressed.\"