NAHANT – The weather forecast for the holiday weekend is picture perfect but Nahant police are preparing for what could be the traffic equivalent of a perfect storm.Police Lt. Thomas Hutton said ideal beach weather, fireworks and the Causeway reconstruction could lead to traffic backups and a shortage of parking.Hutton said the inbound left lane of the Causeway is for beach traffic only and the inbound right lane is for traffic going into town. Hutton urged everyone to stay in the correct lane to avoid traffic tie-ups.”The traffic has been unusually heavy,” he said. “Police will be out in full force to watch for marked-lane violations. We will have extra officers on duty throughout the holiday weekend. We are calling in our reserve officers. A signboard is being put in place, ‘No public parking beyond this point,’ and it will be enforced.”The $20 million roadway and drainage reconstruction project got under way June 10. The project is in the beginning stages with workers having already installed poles in the parking lot for the installation of temporary night lighting, which is necessary for when the outbound traffic is routed through the beach parking lot.Wendy Fox, of the state Department of Conservation and Recreation, said the light poles and staging area reduced the number of parking spots from 1,200 to 850 so parking is limited.”The parking area is all tidied up,” she said. “The inbound and outbound lanes of the Causeway are both open so traffic is not being diverted through the parking lot this weekend.”Hutton said parking in town is limited as well. The only vehicles allowed to park in the municipal lots at Bailey’s Hill, the Lowlands, Town Wharf and East Point are those with 2010 Nahant resident parking stickers and beach parking is prohibited on Nahant Road.”We will not be issuing warnings to violators,” he said. “Anyone parked in those lots without a valid sticker will be ticketed and subject to towing.”The fine for parking in a municipal lot with an invalid sticker is $45 and possible tow costs.”Due to the weather we’ve seen a huge influx in the number of cars in town,” he said. “We’ve seen an increase in the number of cars parking illegally on Nahant Road and other streets in town. It will not be tolerated, because it poses a threat to public safety. Emergency vehicles need to be able to get through.”