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The autumn equinox will occur early morning Monday at 2:30am, making Monday the first meteorological day of fall - and what a day it will be. Completely clear skies, low humidity, and high temps in the low 70s. A picturesque day indeed.
The following day will not be as kind.
Tuesday will for be a partly sunny day for the most part, but the evening hours could explode into thunderstorms. Temperatures rising close to 80 degrees and dew points rising to near 70 degrees will provide ample energy for storms to pop should they occur. Working to destabilize the atmosphere and allow storms to pop will be a strong cold front that moves through in the evening hours sometime between 6pm and midnight. Simultaneously, a disturbance in the upper atmosphere will pass over the area and further destabilize the atmosphere.
Southerly winds at the surface and strong westerly winds up in the atmosphere will allow storms that do pop to become supercell thunderstorms - storms with a rotating core. Supercell thunderstorms have the potential to produce torrential rain, large hail, and even tornadoes on occasion.
Considering all this, the storm prediction center has placed the entire MN-IA border corridor under an area of slight risk for severe weather on Tuesday evening, a level 2/5 designation.
We will be tracking this system as it develops.