WEST MICHIGAN — As the attached photo shows, a rather large upper level low pressure system will be parking itself over the Great Lakes the next few days and controlling our weather. Meteorologically, we call it a cold core cut-off low. Warm core systems are hurricanes, mid-latitude cyclones and upper lows are cold systems with cold air at the center of their circulation. But there’s more…this upper level low (or cold pool of air aloft) is actually cut-off from the upper level jet stream around 30,000 feet that carries these systems across the country from west to east. That said, cut-off lows tend to linger around the region for a few days.
The extensive cloud cover, cold air aloft (which creates instability and rising air), and breezy conditions will keep temperatures running about five to ten degrees below our normal high of 69/70. It will indeed feel like Fall…perhaps only fitting since this is the first full week of it. Fall officially arrived last Thursday morning at 10:21. The image below is from one of our forecast models and is valid for Wednesday morning. It’s a surface map that shows low pressure over the state and the purple represents precipitation chances.
The map below is also valid for Wednesday morning and shows temperatures about 5,000 feet above the surface. Notice the cooler green colors over Michigan instead of the normal yellow colors. Those green tones translate to cooler temperatures both aloft and here at the surface. Most highs will only make the upper 50s/low 60s.
The last map below is also from the same forecast model and same time. It shows the upper level atmosphere at 500 millibars or about 18,000 feet above the surface. Notice the upper level low pressure system directly over the state. This cold pool of air aloft will generate clouds, showers, and below normal temps. Get ready!
In addition to the upper level low pressure system, there will be a few impulses of energy rotating around the low from time to time enhancing the rain shower activity. We’ll also see lake-effect clouds and lake enhanced rain showers thanks to sharply colder air coming air coming across the relatively warmer waters of lake Michigan. Get the complete forecast at www.fox17online.com/weather.
