It's Spring Winter's Over*
A warm-up is coming to the Midwest this weekend that could set a number of record highs in the Chicagoland area. However, a note: this all bears watching because forecasts this far out are subject to change.
"OK Mick, set it up for me."
PART 1. THE LARGE SCALE FEATURES
The unbelievable warmth will be due to a mesoscale ridge of high pressure that will translate over the area and be met with reinforcements. Let me lay it out for you:
Late Thursday a large-scale ridge of high pressure will slide eastward and strengthen as it translates into the Midwest. Here's a map showing 500mb temperatures (25,000 feet above the ground) as warm as -16 degrees Celsius (3 degrees Fahrenheit) stretching all the way up into central Ontario as the main axis of the upper ridge is centered on Minneapolis on Friday:
The ridge will be met with reinforcements on Saturday as it translates slightly eastward, with 500mb temperatures peaking around -12 degrees Celcius (10 degrees Fahrenheit) over Lake Michigan:
By Monday, a surface low pressure will begin to ride up the backside of the powerful ridge and, as it does so, will drag a potent warm front up from the Gulf of Mexico. The strong southerly flow out ahead of the storm should keep temperatures soaring through Tuesday before a weak cold front plows through the area on Wednesday.
PART 2. The important stuff: Beach-weather surface temperatures
So how does it all translate to weather here at the surface? Well, here is Mick's (rough/preliminary) forecast for how these upper-level large-scale features translate to high temperatures (and comparison with the existing record highs at O'Hare airport):
Forecast vs. Record Highs (O'Hare Airport)
Here are the charts from the National Weather Service showing the forecast highs for Friday, Saturday and Sunday:
Warm, warm, warm!
As I stated at the beginning, this all bears watching because forecasts made this far out are always subject to change. That said, the large-scale upper-level features have remained fairly constant in the models for several runs now and there is high likelihood that at least a minor warm-up is in store for the area. Additionally, these forecast highs are liable to change between now and the weekend, with actual conditions being considerably cooler or, even warmer!