If you’re wondering where the cold air is this time of year, you are not alone. A number of my friends have noted on Facebook how late the frost is to Minnesota and the upper Midwest this year and here in the Southeast we are later than normal as well. You can read about some of the temperature records at Weather Underground here. To find the really cold air you have to look halfway around the world at Europe and Siberia, where snowy and cold weather is making life miserable over there (it’s the purple area on the globe map below). We’ve been out of the cold for most of this season, although sometimes the mornings are below normal just because it’s so dry.
But the pattern is about to shift and we will see cold air move into the area by this weekend with a front that is expected to move through the area Friday through Saturday. Frost is probably going to end the growing season in some locations early next week once the cold air settles in, so watch your local forecast for details. James Spann talks about it in his latest blog at https://www.alabamawx.com/?p=107497. Unfortunately, there will not be a lot of moisture with the front, although I would not be surprised to see some rain with it. The air behind it is cooler and drier than now, so it’s not clear how much relief we will see for the wildfires in northern Georgia, the Carolinas and Tennessee. If the front has a lot of gusty winds, that could even make the fires worse.
The Weather Channel discusses the recent tendency for the polar vortex to shift off the North Pole in an article published earlier this week at https://weather.com/science/weather-explainers/news/polar-vortex-shifting-away-from-north-america-climate. This shift may be due in part to the large decreases we have seen in Arctic Sea ice, which changes the energy balance of the most northern latitudes and puts the coldest air over land instead of the Arctic Ocean. You can also watch a video about it at https://abc13.com/weather/global-sea-ice-is-at-a-record-low/1608149/.
I think that as we shift to a more winter-time pattern, we will see the pocket of cold air shift towards us as well. Even though we are in a La Niña pattern (which means generally warmer than normal temperatures over parts of the Southeast in winter) we can still expect to see some cold outbreaks over the course of the next few months. It will be most critical in spring if we get an early warm period followed by a cold outbreak which could bring a late frost to the region. That would have serious consequences for our fruit crops next year.