Frigid February's Finale

Wednesday morning

The coldest part of this week's cold snap is now moving into the Midwest and will be over the Northeast tomorrow night and Friday. This video has more, including a look at what could be a major precipitation producer at the beginning of next week.

This map shows the pervasiveness of the northwesterly flow of bitterly cold air behind a cold front that is contributing to snowfall from Washington, D.C., to New York City this morning. Clearing will follow the frontal passage.

In previous winters, I have talked about the upper stratospheric cold signal, where the normal vortex over the North Pole weakens or actually reverses to form a high pressure. That reversal has often been a sign of impending blocking aloft. In blocking patterns, storms are forced south of their usual paths and it often turns colder. This winter, we have seen that such a setup is not required to make it get cold or snowy. The vortex has remained over the pole all winter, and is rooted in place now, as shown on this map from the University of Wyoming.