Powerful Winter Storm from the Upper Midwest into the Northeast; Severe Thunderstorms in the Midwest and Ohio Valley

A rapidly-intensifying storm is expected to bring heavy snow, blizzard conditions, and icing from the Upper Midwest through the Great Lakes and Northeast. Scattered severe thunderstorms may produce severe/damaging wind gusts and a couple of tornadoes across parts of the Midwest and lower Ohio Valley through the evening. Arctic air will expand across the central and southern U.S.. Read More >

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EHI

The Energy Helicity Index (EHI) is a number which represents the combination of instability and storm relative helicity. Our calculation uses mixed layer CAPE (surface to 3000ft average parcel) and 0-3 km storm relative helicity. Values greater than 2 or 3 have been correlated to cyclonic supercells with increased tornadic potential. Negative values are indicative of an environment favorable for anti-cyclonic (left moving) supercells, but tornadoes associated with anti-cyclonic supercells are extremely rare.

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Powerful Winter Storm from the Upper Midwest into the Northeast; Severe Thunderstorms in the Midwest and Ohio Valley

Convective Parameters - EHI