Potential exists Thursday for widespread thunderstorms to propagate in a west-to-east fashion across the region late afternoon through mid-evening; including the possibility for numerous strong-to-severe thunderstorms which will be capable of producing damaging winds and/or hail with a few tornadoes also possible.
Note: Model graphics being used but not mean that model is being favored, the product is just being used for illustrative purposes.
Forecast models are in agreement that an unseasonably strong shortwave energy embedded within seasonably strong jet traverses New England during the late afternoon and early evening. Forecast models differ within just how strong this shortwave energy will be which will determine the overall strength of the shear.
A warm front lifts northeast across the region during the morning resulting in a surge of high llvl theta-e air characterized by surface dewpoints climbing into the lower 70's. This combined with surface temperatures climbing into the 80's should contribute to a moderately unstable airmass with MLCAPE values as high as 1500-2000 J/KG. One determent to stronger instability may be the mid-level lapse rates. H7 temperatures are forecast to be around +10C with H5 temperatures only around -8C. Forecast model soundings show some warm pockets aloft which would lead to weaker mlvl lapse rates and could prevent stronger instability from materializing.
As mentioned above, dynamics should be rather strong (just a question of how strong) with H5 jet of 40-60 knots and a llvl jet in excess of 30-40 mph resulting in a good deal of speed shear. With the warm front nearby, sfc winds will be more S to SSE with winds changing with direction with height through the troposphere. Winds increasing with speed with height (speed shear) combined with winds changing direction with height will contribute to large hodographs.
As the shortwave approaches, numerous thunderstorms should develop by mid-to-late afternoon and traverse the region through the mid-evening before exiting the coast. Combination of strong wind shear, strong forcing from the shortwave, and moderate instability should yield numerous strong-to-severe thunderstorms which will be capable of producing damaging wind gusts, large hail, and even a few tornadoes. In the event we can materialize steeper mid-level lapse rates a higher end severe threat could materialize.