Tomorrow is the first day of March, and we're seeing the new month's labor pains tonight as severe weather moves across the country's midsection.

Thursday looks to be an extremely active weather day around the country, with the northern middle states expecting several inches of snow and the Southeast in for severe storms.

Right now, it's Kansas and Missouri who are in the bull's-eye of the severe weather. I just went to the Weather Plus set to confer with meteorologist Kristen Cornett on the latest storm news. Kristen was looking at Digital Doppler Plus Radar and suddenly she started practically jumping up and down in amazement.

"This," she told me, pointing to a red dot with a swirl coming out of the lower left corner, "is a classic tornado vortex signature."

Kristen explained to me that the Tornado Vortex Signature (TVS) shows where a tornado is forming. The little swirl in the lower corner shows that the supercell storm is moving in a counter-clockwise direction and is bringing rain into the cell.

These Tornado Vortex Signatures, by the way, are what stormchasers use to know where to point their cars. And it's what allows meteorologists and forecasters to indicate when and where a tornado could hit.

The TVS I've posted here (with the blue circle drawn around it) correlates to this information from the National Weather Service:

Wed. Feb. 28, 7:41 p.m. CST -- Rural Linn County, Kansas:

At 7:38 p.m. CST, National Weather Service Doppler Radar indicated a severe thunderstorm capable of producing a tornado. This storm appears to have cycled and looks to be restrengthening. Additional tornadoes appear likely in the next several minutes. This dangerous storm was located 6 miles north of Blue Mound (Missouri), or 8 miles west of Mound City, moving east at 35 mph.

This dangerous storm will be near 2 miles north of Mound City by 7:50 p.m. CST.

As the saying goes, you learn something new every day. But though I can now spot a Tornado Vortex Signature on Doppler radar, I'll leave the forecasting to the meteorologists.