A complex atmospheric pattern is expected to unfold on Saturday, and the evolution may lead to the potential for strong to severe thunderstorms in the Northeast states. As a mid level ridge builds toward the area from Friday Night into Saturday, a disturbance associated with a thunderstorm complex in the Northern Midwest states will ride over the top of this ridge, eventually diving southeast from Southeast Canada into the Northeast on Saturday. But, as you can imagine, forecast models are struggling with the exact details of its movement through the area.
Convection, inherently, is difficult to forecast. Models are likely to struggle with this disturbance as thunderstorms develop today over the Northern Midwest and head toward parts of the Great Lakes. More importantly, this disturbance will move northeastward into Southeast Canada, along the periphery of a mid level ridge, and then dive southeastward into our area later Saturday — and the timing of its approach becomes critical to the forecast.
As the disturbance is dropping southward, atmospheric instability will be rapidly increasing from the west. With the building mid level ridge will come an axis of surface based and elevated CAPE (Convective Available Potential Energy) as well as more favorable lapse rates (temperature change with height in the atmospheric column). Most notably — also arriving later Saturday will be favorable wind fields and shear for thunderstorm organization.
The ingredients for strong to severe thunderstorms — in fact, an organized severe thunderstorm event — are all expected to be present by Saturday afternoon and evening. But the disturbance we mentioned above may wreck that entire setup by moving through the area during the late morning to early afternoon. Such an occurrence would overturn the atmosphere, with rain and non-severe thunderstorms moving through, and stabilizing things further. Behind that disturbance would be more stable air and a minimized threat for severe storms.
If the disturbance were to slow down, or speed up, the atmosphere could be primed for strong to severe thunderstorms by Saturday afternoon and evening. But uncertainty, as we mentioned above, is quite high. The convective nature of the event suggests that we may not know exactly how things will evolve until Saturday morning, when satellite/radar imagery and upstream observations can be fully analyzed.
The Storm Prediction Center, recognizing the potential, has placed our entire area in a Slight Risk for severe thunderstorms, and mentioned the potential for “both supercells and an organized convective system”. But, the uncertainty we mentioned above also is rooted in their forecast, and so no further risk areas or probabilities were added beyond the “Slight Risk” area for now.
Stay tuned through tonight and into Saturday morning for the latest information. Premium Members can expect another video this afternoon and a technical discussion by evening on what we expect to unfold on Saturday throughout the area.