What the groundhog is to spring, Santa Claus is to retail Christmas sales.

This year all signs point to a modest increase according to Western Temporary Services' "Santa index." The index predicts that when orders for temporary Santas go up, retail sales will be soft. In strong selling seasons, orders for Santas will be down.Jenny Zink, vice president and national program director of Western's marketing and Santa divisions, which provides Santa's to stores during the Christmas season, said many retailers think the '88 season will see a modest increase in sales.

"We've noticed over the years that when retailers are worried about sales, they hire more temporary Santas in order to attract children with their gift-hunting parents," said Zink. Western's Santa sales this year are running slightly behind last year's.