Cold weather is here: will it last?

The cold weather did indeed arrive--the high today in Madison was only 20 after a morning low of 10, 20 degrees below normal. Milwaukee was not much warmer at 22 and 15. Temperatures in Madison have been 20 degrees above normal recently in both September and October, but it's been since last winter that we've seen 20 degrees below average. It looks like we'll see a bit of a warmup in the next few days, with 40s possible on both Sunday and Monday, which will probably feel very comfortable after the 20 degrees today. However, the eastern-US upper level trough that is causing our cold weather now looks like it may return by Tuesday and Wednesday, with another couple days of very cold weather possible by then. After that, the exact location of the boundary between warm weather in the west and very cold weather in the east will determine whether we're going to be warm, cool, or frigid. It looks like a good bet that in the 7-14 day time frame Colorado will be warmer than average and Maryland colder, but for Wisconsin it's still uncertain.