It looks like the Storm Prediction Center will be issuing a tornado watch for portions of upstate New York and Pennsylvania shortly. Parameters look fairly impressive for supercells later today in areas such as Binghamton, Scranton, State College, and maybe even Albany.
For a major severe weather event you need to have a combination of parameters come together.
- Vertical Wind Shear
- Triggering Mechanism (cold front, dry line, etc.)
The first 2 parameters are certainly in place as you can see in the 2 images below. The first image shows MLCAPE or mixed layer CAPE which is over 2500 j/kg across portions of upstate NY. This is VERY impressive and indicates the potential for violent updrafts when air parcels reach their level of free convection.
The second image is 0-6km bulk shear which is essentially the amount of wind shear (directional and speed) between the ground and 6km in the atmosphere. The more wind shear the more likely storms can rotate (and create even more violent updrafts) and the ability of storms to organize. Shear >30 knots is enough for storm organization and supercells.
The third ingredient, a triggering mechanism, is a bit more tricky. A mid level trough in the Great Lakes is slowly oozing east and that may provide enough “lift” when coupled with weak surface boundaries (differential heating, lake breeze fronts, etc) to initiate convection. Once convection is initiated it will quickly go severe with the above parameters in mind.
As for Connecticut it’s possible a renegade cell will make it into Litchfield County this evening but for the most part we will remain “capped” and the severe threat will remain northwest of us.