Get ready! It looks like we could have our first real dose of arctic air invading the Midwest by this time next week. Long range computer guidance suggests some bitterly cold wind chills could spread across the Midwest when we head back to work or school next Monday.
I’m betting on this chunk of Arctic Air to make it here. Here’s why.
1) Source region
Whenever the models are hinting at cold air outbreaks or heatwaves there is often a source region from which this air mass originates. Let’s check out the current temperatures in the Northwest Territories and the Yukon of western and northern Canada.
Four to eight inches of snowpack over vast stretches of Canada coupled with shorter amounts of daylight are leading to increasing reports of single digit temperatures over a wide area of Canada.
Check it out - just 7 degrees in Stony Rapids! That’s our source region for this upcoming expected cold air outbreak. But how do we get that air down here into the United States and more specifically the Midwest?
2) The Jet Stream
The upper level river of wind blowing about 25-thousand feet off the surface of the earth is expected to become highly amplified later this week. Remember the jet stream forms where there are air pressure or temperature differences, and as you can see on the map below, there is a quite a temperature contrast between dry and warm California and the bitterly cold Great Lakes and Hudson Bay.
There is also a huge pressure disparity. It’s not the Polar Vortex but a strong vortex or low-pressure area aloft develops near Hudson Bay. This intense area of low pressure helps to generate the strong winds aloft. I’ve placed an “L” at the point where the air pressure aloft is the lowest.
Since winds flow counter clockwise around and toward the center of low-pressure areas, the jet stream winds shown here are flowing from the source region of bitter cold air in Canada, south into the United States. The conveyor belt of cold, if not frigid air, is being transported right into the heart of the country.
3) What’s that mean?
It means get ready for the coldest morning lows and coldest daytime highs we’ve seen since last Winter. Right now, the chance of snow is too iffy for me to post any graphics. That wouldn’t be fair as it will likely change but it is fair to post a wind chill graphic for next Monday morning. At this point, it looks like our first finger numbing wind chills of the season will be nipping at our nose and toes.
So, dig deeper into the closet and find the Winter hats and gloves. We’ve had a couple of glancing shots of cold air so far this Autumn but next week’s shot cold air will feel more like a direct impact.
Don’t forget to download our Storm Track 5 Weather App so you can stay out ahead of the colder air.