UPDATE 1-Target December same-store sales up 4.1 percent

(Adds January forecast, other details)

CHICAGO, Jan 4 (Reuters) - Target Corp. (TGT.N) said on Thursday that December sales rose 4.1 percent at its stores open at least a year, shy of Wall Street expectations, in the busiest shopping period of the year.

Analysts on average had expected the second-largest U.S. discount retailer to post a 4.5 percent increase, according to estimates gathered by Reuters.

Total sales for the five weeks that ended on Dec. 30 rose 9.9 percent to $9.25 billion.

Target said health care, electronics, and newborn and infant goods were among the best-selling categories, while jewelry and intimate apparel were weaker.

Many retailers struggled with poor demand for clothing in an unusually mild December. Target stores visited in the Chicago area had many racks of clearance-priced winter clothes on display over the past two weeks.

For January, Target said it expected same-store sales growth of 3.5 percent to 5.5 percent, adjusted to exclude an extra week compared with a year ago.

Retailers typically operate on a fiscal calendar that ends in January. For the current fiscal year, the retail sales reporting calendar includes a 53rd week, which skews comparisons with last year's 52-week year.

Target said it would report January sales two different ways, with one figure adjusted to exclude the extra week and the other including it. The company did not provide a forecast for same-store sales growth including the additional week.