A surge of theta-e air will push into southern New England over the next couple of days and with this we will see an increase in precipitable water values (PWATS) upwards of 1.5'' to 2+'' at times and dewpoint values approaching the lower to mid-70's, especially come Thursday:
While mid-level lapse rates aren't expected to be overly steep (700mb-500mb lapse rates in order of perhaps 6-6.5 C/KM), surface temperatures expected to warm into the 80's combined with the rich low-level moisture will allow for moderate instability to develop Thursday afternoon with surfaced-based cape (SBcape) values perhaps exceeding 2500-3500 J/KG and mixed-layer cape (MLcape) values exceeding 1500-2000 J/KG:
With a frontal boundary to the north and approaching shortwave energy, we will see an increase in the mid-level wind fields as the day progresses on Thursday. Computer forecast models shows a 50+ knot 500mb speed maximum pushing right through southern New England during the mid-to-late afternoon hours with also an increase in the low-level jet at 850mb. The increase in shear (especially in the middle levels of the atmosphere will contribute to 30-40 knots of effective shear and 0-6km shear which is plenty for any thunderstorms which do develop to become organized:
This point-and-click forecast sounding for a location in southern CT shows the potential atmospheric conditions on Thursday. Highlighted with the white circle shows plenty of shear throughout the troposphere and circled in blue shows even the potential for low-level winds to remain a bit backed. This is evident in the forecast hodograph also circled in blue. This means there would be the possibility for a thunderstorm to begin to rotate if it became strong enough. Circled in red also shows strong shear values present through several key layers in the troposphere:
While there are kinks to be worked out with regards to timing, any cloud cover leftover from any morning activity, etc, as it stands right now we are looking at the potential for a rather active Thursday afternoon across southern New England with numerous showers and thunderstorms expected to develop. Given the ingredients mentioned, several of these thunderstorms could become strong to severe and pose a threat for strong to damaging wind gusts, hail (perhaps even large hail if any storms rotate), and flash flooding given presence of rather high dewpoints. The details will continue to be fine tuned over the next 24-36 hours.
