BARC operates from Blue Hill Observatory in Milton on SKYWARN Recognition Day in December. It is possible to drive to the observatory on SRD; the access road (labelled Summit Rd. on the map) is just north of the Trailside Museum on Route 138.
The observatory is also about a thirty-minute hike from the parking lot next to the Trailside Museum. The observatory is home to the longest continuous weather record in North America; its web page is here.
Public transportation options are unfortunately not very good, though carpooling can be arranged.