KMSP - During the summer, especially the month of August, the atmosphere in the United States is typically warm and muggy. Doesn’t take a rocket scientist to figure that out, but this will often lead to very little mid latitude cyclone activity… what you would call a low pressure with a cold front… or a storm system. Most of the precipitation in the U.S. during the summer comes from instability thunderstorms. There is so much heat and so much moisture in the atmosphere that thunderstorms will just form almost anywhere and can put down some tremendous rains. Well, this week will be a bit unusual. An extremely strong low pressure for this time of year will push its way into and through the Upper Midwest… something we haven’t seen in the month of August in over half a century. This will lead to widespread rain and MUCH cooler temperatures.
Just watch how this storm will likely “bomb out” in Minnesota. This term refers to the rapid intensification of the area of low pressure. Below are a set of images that show vorticity in the atmosphere… AKA spin, or where our area of low pressure is located. In the first image I have circled where the low pressure is located.
It’s amidst all the color over western South Dakota… or more accurately “is” the color in South Dakota. The image I grabbed is the forecast for Monday night. Now look at it again for Tuesday and Wednesday nights.
Pretty hard not to notice a change. The black lines, or the lines indicating height, circle around the center of this low which shows that there is literally a hole in the atmosphere right there… aka “low” pressure. This thing gains an ENORMOUS amount of strength in just 24 hours and then continues to intensify as it pushes northeast through the state. This will undoubtedly bring rainfall and cooler temperatures. But just how much and how cool? Well, since nothing like this has happened in many of our lifetimes during the month of August, it’s really a very big guess. BUT, we have a general idea. Here is what some of our forecasting models are spewing out for rainfall totals and temperatures Wednesday afternoon.