NEW YORK — Broadway’s midwinter blues don’t seem so blue this year.Late January usually sees Rialto grosses continue their annual post-holiday slump, but this year — surprise! — biz was up for the week ended Sunday. Tally rose some $700,000 over the previous week, bringing in $14,846,423 for 26 shows on the boards. That’s a solid bump over the $13.3 million peak the sesh hit in 2003 with 31 productions up and running. Perhaps the unseasonably warm weather spurred some impromptu trips to Gotham, or maybe shows are beginning to reap the rewards of the discount pricing many deploy to boost sales during the winter chill. In any case, the productions that saw a drop in sales didn’t see much of a dip. None fell more than $40,000. Climbing nearly $70,000, “Hairspray” ($549,658) saw the biggest bump, not counting “The Odd Couple” ($840,040), back up to capacity numbers after Nathan lane’s laryngitis caused the cancellation of three perfs the previous week. “The Pajama Game” ($425,265) played its first full week of previews and had an added $42,000 to show for it, while “Barefoot in the park” played to around 60% capacity and took in $284,991 for its first eight perfs. And the four-show guest appearance of Dick Van Dyke worked magic for “Chita Rivera: The Dancer’s Life” ($338, 623), pushing up grosses by more than $50,000. Can a visit from Lisa, Rivera’s “Rink” co-star, be far behind? The 20 musicals grossed $12,600,212 for 84.9% of the Broadway total, with attendance of 166,643 at 78.5% capacity. Average paid admission was $75.61 for musicals, $67.54 for plays and $74.27 for all shows.