Temperatures will warm into the upper 20s tomorrow, combined with dewpoints in the low 20s, resulting in a great deal of CAPE, likely over 2000 j/kg (with some models featuring over 3000 j/kg).
However, shear will likely be on the marginal side, but as CAPE increases, the balance needed to achieve severe weather begins to tip in favour of CAPE, especially with values over 2500 j/kg. 500 mb winds to 30 kt should be sufficient to promote some storm organization and damaging wind gusts, when combined with mid-level dryness as shown here
Another major concern is storm motion. The following 06Z NAM sounding from the Montreal area depicts an estimated storm motion (mean 0-3 km wind) of only 13 kt, which is only about 23 km/h, which may result in very heavy rainfall amounts in some areas due to the storms.
The potential for large hail also accompanies some of the stronger cores, especially with relatively low WBZ levels. As late week demonstrated, modest CAPE (considerably less than here) and weak bulk shear yielded large hail in various locations.
Severe thunderstorms may also occur in the Montreal area and points east on Saturday, but timing and parameters are still highly debatable.