Monday, May 20, 2019 New England Convective Potential

During the day Monday a cold front will be pushing towards New England. Out ahead of the cold front it will be warm and on the humid side with temperatures pushing into the 70's and 80's with dewpoints into the 60's which will yield a modestly unstable airmass.

T'storm coverage may not be very widespread on Monday (perhaps a greater coverage across central and northern New England) given the main shortwave energy tracks just north of the U.S./Canadian border:

Wind shear will be more than supportive for some t'storm develop with a 50-60+ knot mid-level jet punching through New England and a low-level jet of 35-45 knots over the region. This will contribute to both strong vertical and effective shear which will favor the potential for organized and sustained updrafts:

Some forecast soundings also indicate the potential for a little bit of directional wind shear in the lowest 5,000 feet of the atmosphere (winds changing direction with height). Circled in red on the bottom right shows winds slightly changing direction with height and this is shown via the curved look to the hodograph on the top left. Something to watch as Monday progresses as this could increase the potential for some supercell-type structures:

Due to weak mid-level lapse rates (temperatures not really decreasing sharply with height between 10,000 and 20,000 feet) this will limit the degree of destabilization that will take place. However, the combination of temps into the 70's and 80's with lower 60's dews will yield anywhere from 1000-1500 J/KG of MLCAPE which is more than enough for some t'storms to develop given the wind shear aloft.

What can we expect? With the strongest overall forcing (thanks to the shortwave tracking north) remaining north, lack of steeper mid-level lapse rates, and greater instability, t'storms will be more scattered in nature. Given the wind shear parameters though, a few t'storms may become strong-to-severe posing a threat for hail (perhaps as big as 1'' to 1.25'') and damaging wind gusts. If the degree of directional wind shear becomes a bit stronger than advertised an isolated brief tornado can't be ruled out either.

We are not looking at a widespread severe weather event (or even widespread t'storms) but more scattered in nature with a few becoming strong-to-severe. Timeframe will be from 2:00 PM until 8:00 PM. Activity quickly diminishes and weakens as the sun sets.