Sunday, April 19, 2020

Gusty Thunderstorms with Small Hail Possible Tuesday, April 21, 2020.

A vigorous shortwave trough is expected to amplify (strengthen) as it digs through southeast Canada Tuesday:



Associated with the shortwave trough will be a pool of very cold temperatures between about 10,000 feet and 20,000 feet above the ground with temperatures up around 18,000 feet around -25C (-30 diving through southeast Canada!). This will provide steep mid-level lapse rates (temperatures decreasing rapidly with height):


With such a vigorous shortwave we will also see some rather impressive dynamics aloft characterized by the nose of a mid-level jet streak of 80+ knots punching into the region with a low-level jet exceeding 40-50 knots:

Mid-level jet:



Low-level jet:


With temperatures climbing into the 50's with dewpoints into the 40's combined with the steep mid-level lapse rates this will yield a marginally unstable airmass. Combination of a marginally unstable airmass, strong dynamics, and strong forcing from the cold front and shortwave energy will likely be enough to spark off scattered showers and thunderstorms Tuesday afternoon. Some of these will be capable of producing gusty winds and/or small hail. The greatest overall risk looks to be across NY, northern PA, and VT, however, depending on overall timing some of these may sneak into parts of MA and CT before fizzling due to loss of daytime heating. These will be scattered so not everyone sees any thunderstorms or even rain. 

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