A cold front is set to sweep across southern New England early Wednesday evening. Combination of marginal instability and rather strong dynamics and forcing from the front will promote the development of a low-topped squall line ahead of the cold front. While the greatest overall potential for damaging winds and even hail exists across New York and Pennsylvania, localized embedded damaging wind gusts and hail will be possible across southern New England (particularly western and central sections).
Instability is not the driver here with temperatures predominately in the 60's with dewpoints into the 40's and lower 50's, however, steep mid-level lapse rates (~7 C/KM) will aid in the development of marginal instability characterized by about 500-750 J/KG of mixed-layer CAPE.
The driver is going to be the strong forcing associated with the cold front and very strong jet stream dynamics which are characterized by 50-60+ knots at 500mb (~18,000 feet above our heads) and 35-40+ knots at 850mb (~5,000 feet above our heads). These shear values are more than enough to support the development of organized convection.
The line initially develops across western New York and central Pennsylvania and rapidly progresses east through the afternoon and evening. Combination of dry low-level air and strong low-level winds will support the potential for damaging wind gusts on the leading edge of the squall line. Wind damage may be more scattered across New York and Pennsylvania but then become more isolated across New England. Given cold mid-level temperatures characterized by -20C at 500mb (~18,000 feet) some of the more robust convection within the line could even produce some small hail. The line is likely to move across Connecticut between 5:00 PM and 8:00 PM Wednesday evening likely causing some localized damaging wind gusts on the leading edge and even potential for some small hail:
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