Much colder than normal temperatures continue today from the Northwest into the north-central U.S. and are spreading through the Midwest and toward the Mid-Atlantic and Northeast. However, above to much above normal temperatures will prevail along the Gulf Coast and in the Southeast today and into tomorrow. It's the time of year that makes a 5-day forecast resemble a roller coaster with incredible highs dropping to extreme lows. 

Here in Oklahoma, we know that if there is a very warm day in December, it will probably be followed by bone chilling cold. It's as if Mother Nature is playing a bad joke on us by making us think the worst is behind us. In reality, the worst is about to hit like a Mack truck.

Below is an image indicating temperature anomalies for Friday, Saturday and Sunday. A temperature anomaly is a term means a departure from average. A positive anomaly (yellows, oranges, reds) tells us the observed temperature is warmer than average, while a negative anomaly (blues, pinks, grays) says it is colder than average. 

Those living in the Southwest and south-central states will have a wonderfully warm Friday. Eastern New Mexico and parts of West Texas will be 15F above normal. If you haven't put up your outdoor Christmas lights, that will be your best bet. 

Meanwhile, a very cold arctic air mass is expected to develop in western Canada and the Northwest before then advancing south. Temperatures will drop steadily on Saturday with areas in and near Montana encountering a 30 degree departure from normal. 

By Sunday, nearly the entire nation, with the exception of the East Coast, will be located in areas experiencing a negative anomaly. Places like Texas Panhandle will go from around 15 degrees above normal to 15 degrees below normal. 

So, don't be caught without your coat and gloves on Sunday just because it felt fine without them the day before. The cold air is coming and that roller coaster is about to take a dive.