Upper-level low pressure dives southwards into New England through the day Sunday while briefly closing off at H5 during the day Monday. Associated with the upper-level low will be an impressive cold pool characterized by H5 temps around -13C to -15C with mid-level lapse rates on order of 6.5 C/KM. This combined with surface temperatures ranging between the upper 70's to lower 80's with dewpoints into the lower 60's will contribute to modest CAPE with MLCAPE values on order of 1500 J/KG. Wind shear in the lowest 10,000 feet will be extremely weak, however, the region should be brushed by stronger 700-500mb winds on the southwestern side of the upper-level low.
Based on the above, scattered-to-numerous showers and thunderstorms should develop by late morning to early afternoon across northern New England and progress southwards through the remainder of the afternoon. Combination of unseasonably cold mid-level temperatures, modest instability, and roughly 30 knots of bulk shear should be sufficient for storms to become organized. The strongest thunderstorms will be capable of producing hail (perhaps > 1'' in diameter in the most intense cores) and strong wind gusts. The weak low-level winds will mitigate the damaging wind gust potential, however, inverted V forecast soundings favor potential for localized damaging wind gusts, especially as any of the stronger cores collapse.