I am just going to start off by saying
WE ARE NOT LOOKING AT A WIDESPREAD, HIGH-END SEVERE WEATHER EVENT
While we are lacking an elevated-mixed layer, it is important to note that EML's are important when seeking out the potential for a widespread, high-end severe weather event. You can still get severe weather and even numerous severe storms/damage but typically mostly everything falls short of high end.
Now that we got that out of the way let's get into it.
An elongated stationary boundary is currently positioned from off the New England coast across central New England, though the Great Lakes, and into the upper-Midwest. Shortwave energy within the north-central Plains and upper-Midwest is expected to amplify as it traverses the Great Lakes region resulting in strengthening low pressure at the sfc. This will help push the stationary boundary within New England northward as a warm front overnight and early Sunday morning. Thus, very warm and humid air advects northward.
With the amplifying shortwave trough and strengthening sfc low, the response will be increasing shear across the Northeast and New England characterized by bulk shear values in the 40-50 knot range. These values are more than sufficient for convection to become organized and even acquire supercell characteristics. In addition, llvl winds are expected to back in the vicinity of the warm front, yielding enlarged hodographs and 0-1km helicity values 150-200+ m2s2 and 0-3km helicity values 200-250+ m2s2. These values are more than sufficient for the more mature thunderstorms to become supercells.
Combination of temperatures rising into the 80's and dewpoints climbing into the lower 70's will yield a moderately unstable airmass characterized by mixed-layer CAP values in the 1500-200 J/KG range. Weak mid-level lapse rates, ~6 C/KM, will hold the atmosphere back from becoming more unstable. However, should dewpoint pooling occur, which is possible within the Connecticut River Valley, dewpoints could climb into the 74-76F range, this may yield a zone of mixed-layer CAP values in the 2000-2500 J/KG range and compensate a bit for the weaker lapse rates.
Scattered-to-numerous thunderstorms should begin developing by early afternoon across NY/PA ahead of the cold front with thunderstorms developing across eastern NY and western New England by mid-afternoon ahead of the pre-frontal trough. Given the ingredients mentioned, the strongest thunderstorms will be capable of producing damaging wind gusts and hail. Should any discrete, mature cells develop, given the strong wind shear, the potential also exists for a few tornadoes.
High PWATS should also yield potential for localized flash flooding.