The snowstorm that pounded the East Coast over the weekend helped keep Broadway box office buried — although given the time of year, sales probably would have been pretty slow anyway.Every single show on the boards was down compared to the prior week, with the sole exception of “Rock of Ages” ($368,708), which managed to rise $761. Blizzard-related transit issues must have played a role in the downturn; even if Gotham wasn’t hit too hard, areas outside the city — include Long Island, Connecticut and other suburban enclaves from which a notable chunk of Rialto auds originate — had to dig themselves out from under far greater accumulation. So all Broadway shows may have gone on as scheduled, but the weather likely kept even some ticketholders away, which would have shown up in the week’s grosses as refunds or exchanges for future weeks. Walk-up biz for the weekend took a hit, too. In any event, producers were probably already braced for the worst even without a snowstorm, since this mid-February frame is often one the Main Stem’s slower periods prior to the pickup of spring-season momentum in the coming weeks. As has become common during Rialto-wide downshifts, barely-wavering “The Book of Mormon” ($1,590,782) led the charts ahead of “Wicked” ($1,355,055), “The Lion King” ($1,333,769) and “Spider-Man: Turn Off the Dark” ($1,002,910). Biggest dip of the frame was logged at previewing musical “Cinderella” ($721,654), but don’t write off that tuner’s boffo prior seshes just yet — the show only played seven previews, one fewer than the eight it logged the previous sesh. “Annie” ($696,830) and “Nice Work If You Can Get It” ($518,472) also took notable hits, with “Nice Work” playing to auds at less than 55% attendance. Overall sales slid almost $1.5 million to about $15 million for 22 shows on the boards. Attendance plummeted more than 18,000 to 162,547, a tally that’s also notably lower than the 177,602 posted during the same week in 2012. At least there’s some growth potential headed the Main Stem’s way this week. Valentine’s Day date nights can sometimes provide a clear boost in B.O., and the long President’s Day weekend also is poised to bring in more traffic.