How long will the bitter cold last?

The pattern that will bring widespread sub-zero readings and record lows tonight looks like it will stick around for quite some time. 

Here are the forecast lows tonight. Areas in the lighter shades of purple will fall below zero.

While there will be a very modest moderation in temperature from time to time, several more lobes of unusually cold air are poised to sink southward right through the end of the month.

Ahead of each new push of cold air, there will be the possibility of snow, freezing rain, or rain - including this weekend. 

Take a look at a week from Friday - February 27 - when another push of 20-degree-below-normal air pushes in.

The next several images show the 5-day average temperature anomaly into early March. Areas shaded in blue indicate unusually cold air.

Finally, by early March, there are signs that the pattern could shift and allow a return to more normal temperatures.

Thus, it looks like a sold 2-week period of unusually cold air over most of the eastern half of the nation.