The leading edge of the Arctic air filtering into the U.S. is abrupt and ruthless—temperatures in Iowa at 4:00 PM ranged from 72°F in the southeastern corner of the state and 27°F with a wind chill of 11°F in the northwestern corner of the state. Ahh. Or brrr, depending.

The cold front is very apparent on Theta-E charts, which takes into account both the surface temperature and moisture in the air—sharp gradients indicate the leading edge of a cold or warm front. There's no mistaking where the cold front is on this chart.

The not-a-polar-vortex will continue to flow south through most of the United States through the end of the week. By Friday, highs will struggle to climb out of the 50s as far south as southern Texas and the Florida Panhandle, let alone highs in the 30s as far south as Oklahoma and Tennessee.

The cold front will continue marching south, reaching Texas tonight with a similar thud:

Ouch. Happy winter.

[Images: Iowa Mesonet, SimuAWIPS, NWS EDD]

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