NEEDHAM — Neighbors have been watching as a new 9,000-square-foot farm stand, three times the size of its predecessor, emerged on the corner of Forest Street and busy Central Avenue. The yearlong construction at 95-year-old Volante Farms (51 years at its current location) is over. The new premises, with a clean barn-like interior, have plenty of room for the farm’s own produce, fruits and vegetables raised locally or shipped in, grass-fed New England meat, a deli, a bakery, and an ice cream stand. And for the first time in its history, the business will remain open year-round. Opened two weeks ago, the multimillion dollar expansion was guided by the fourth generation of Volantes.