National Weather Service United States Department of Commerce

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 >

Automatically generated image showing areas of the significant tornado parameter.

 

Thumbnail of an automatically generated image showing areas of the significant tornado parameter. Thumbnail of an automatically generated image showing areas of the significant tornado parameter. Thumbnail of an automatically generated image showing areas of the significant tornado parameter.
Hour - 1 Hour - 2 Hour -3

4 Panel Display | Animated Loop

Significant Tornado (SigTor) 

A composite index that includes 0-6 km bulk wind shear, 0-1 km storm-relative helicity, surface based CAPE, surface parcel CIN, and surface parcel LCL height. Values greater than 1 are indicative of increased potential of significant tornadoes.

The contours are the Lifted Condensation Level or LCL.  A lower LCL typically increases tornadic risk because it is indicative of air parcel acceleration occurring closer to the surface. 

 

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