Above is a map of current temperatures across North America. The large purple area covering much of central Canada, the Arctic Ocean, and Greenland, has temperatures below zero now, and some are below -20 F. We didn’t get any significant cold air flush outs in October (when it was still going above 100 F in parts of Alabama, Mississippi, and Georgia), but the sun angle has been low up in the Arctic for a while now and the days very short (0-7 hours long). So, cold air has really built up.
Over the next 2-3 days, a large upper-level ridge will build into Alaska, and the upper-level convergence on its east side will produce a large high pressure area in western Canada. Cold air is more dense and therefore heavier than warm air, and that will intensify the developing high pressure area. The shallow cold air will start to try to flow out of the dome of high pressure, but it will be blocked to its west by the Rocky Mountains, so it will be forced southeast into the U.S. starting this weekend.
This is a very large and cold air mass. So its own weight, combined with the favorable upper-level ridge to the west keeping pressures high, and a surface low pressure area forming near the Great Lakes, will push this Arctic air deep into the central and eastern United States. By Tuesday evening, temperatures at 850 mb (about 5,000 feet) will be as much as 21 C (nearly 40 F) below normal for mid-November across most of the U.S. east of the Rocky Mtns.
A significant cold front will move through the Southeast US Thursday and Thursday night, with lows dropping below freezing north of I-20 (places like Little Rock, Nashville, Huntsville, and Chattanooga), and high temperatures Friday into the weekend will only be in the 40s and 50s over many areas. But this is not the main event. That moves through next Monday and Tuesday. Below is a graph of our predicted temperatures every 6 hours at Birmingham airport.
So, here we sit today near 70 degrees, we will drop to near freezing by Friday morning, have a normal, chilly weekend, then the cold blast will come Monday night. Temperatures will drop very quickly from the 50s in the early evening to the lower 30s by Tuesday morning, stay in the the 30s all day on Tuesday (with wind chills during the day in the 20s), then drop to near 20 degrees by Wednesday morning.
We have high confidence in this cold outbreak because of the ridge over Alaska and the large pool of cold air over the Arctic and Canada. Plus, all 3 major computer models (the American GFS, the Canadian GDPS, and the European ECMWF) all show this happening. A zoom-in on ECMWF model projected temperatures around the Birmingham metro ares on Wednesday morning is shown below.
We didn’t have that much cold air last Winter, and if this pattern were to set up again in December or January, we could easily see temperatures near zero here in Alabama. With this cold outbreak next week, some locations in Arkansas and Tennessee may drop into the single digits, and a little snow is even possible, especially in the mountains of east Tennessee and western NC. This will be the coldest air since January 30, 2019 here in Alabama.
Interesting to note that the temperature hit 101 degrees on October 3 in Birmingham. If we drop to 21 next week, that will be an 80 degree drop in temperature in less than 45 days. This large of a temperature drop in 45 days has only occurred 5 other times since 1900.
This is the kind of cold air outbreak than can freeze pipes, kill plants, and harm animals. Go ahead and think about winterization around the home, such as covering outdoor faucets, draining water hoses, and winterizing boats. Make sure your antifreeze is good in your car and your tire pressure is sufficient (it will drop significantly next week). Once the cold air arrives, if you want any plants to live, bring them inside or cover them. Also remember that it is sometimes up to 5 degrees colder right near the ground than the official 2 meter temperature, so bring pets inside or at least make sure they have plenty of warm stuff to use inside a dog house, and dog house doors should never face north or west. Check on any elderly or disabled people you think might not have sufficient, safe heat. And check your own heating system if it hasn’t run this year.
Dr. Timothy A. Coleman
Coleman and Knupp, LLC
http://www.colemanandknupp.com (check out our new website!)