Big Changes Lay Ahead in the Weather World for Illinois & Wisconsin

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If you pay close attention to weather-related posts on social media, you may have heard about a big pattern change that is set to occur later in November.

If you haven’t seen any article about that pattern change, this one will explain what our meteorologists believe will happen during the middle of the month.

First, let’s rewind a bit and reflect on September and October. Each month finished well-above average in the temperature department. September finished as the 2nd warmest September ever. October finished 5° above average overall.

That warmth has extended into November, and will remain in place through roughly the first half of the month. The image above on the right shows the pattern that has and will continue to be in place: a ridge.

Essentially, the western United States has seen a trough with active and cooler weather. In turn, because weather has to balance itself out, warmer and less active weather has existed immediately to the east of that trough in the west. That is why the Plains, Midwest, Great Lakes, Missouri Valley, Ohio Valley, Southeast, and Mid-Atlantic have seen much above average temperatures thus far this fall.

Things won’t stay that way through the remainder of the fall.

A significant pattern change has and continues to look likely somewhere during the middle of the month. Many variables that our meteorologists use to analyze long-term weather patterns point to a change somewhere around the 12th-15th of November.

And typically, when multiple meteorological variables continue to advertise roughly the same outcome, it has a noteworthy chance of happening.

Take a look at the map on the left. That represents the pattern that looks probable during the middle and latter half of the month. The pattern essentially flip-flops. A trough (cold and more active area) is in place over the middle and eastern sections of the country. Consequently, a ridge (warmer and less active) pattern exists across the western US.

That means the gates will be open for the colder air in Canada to filter into the eastern two-thirds of the country. It’s impossible to project exactly what kind of temperatures will occur, but highs in the 40’s and lows in the 20’s and 30’s certainly appears plausible later this month.

Of course, in order to get a significant pattern change like this, a strong storm system has to move through to switch things up. That does look likely somewhere between the 12th and 16th. That system will alter the pattern and organization of the atmosphere, which translates into a colder and possibly more active end of November.

Does this mean snow is in the forecast? No. But with a strong storm system drawing in what likely will be much colder air later this month, wintry precipitation certainly isn’t impossible.

If anything, an end to our very warm temperatures and a dose of reality and winter will occur for the eastern two-thirds of the country. All good things come to an end, right?

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