A cold front...actually more of a dewpoint front...will move
eastward into this hot unstable air mass Thursday afternoon and
evening. Wind fields aloft will strengthen as a weak mid-level
trough moves through as well, with 30-40 kt of deep layer shear.
Surface-based CAPE of 2000-3000 J/kg and MLCAPE of up to 1500
J/kg indicates plenty of instability. One thing lacking for
severe weather will be relative lack of height falls. But model
vertical motion is strong and the instability and shear should
be sufficient for the development of strong to severe
thunderstorms from as early as 11 AM or Noon and lasting into
the mid-evening hours.
The CAMs indicate potential for broken line segments with the
main focus across CT and western and central MA, where updraft
helicity swaths are focused. Damaging wind appears to be the
primary severe threat, but an isolated tornado cannot be ruled
out in those areas. The least threat is in RI and southeast MA,
where the majority of the day should be dry, but remnant
showers and thunderstorms may move through late in the day or
evening.