Tornado outbreak of December 1-3, 2019

the Tornado outbreak of December 1-3, 2019 was a unusual and very prolific late-season tornado outbreak which struck the upper Midwest and Great Lakes region during early December in 2019. The outbreak was the result of a strong frontal system moving eastward through the region, in combination with moisture from the Gulf of Mexico and warmer air from the southeast, as well as cool air from the north. This combined to create strong to severe thunderstorms in the Dakotas on November 30, and as they moved into the Great Lakes region the following morning, the storms became tornadic. In total 131 tornadoes touched down, including several EF4 tornadoes. The worst effected states were Illinois, Indiana, Ohio and Michigan, with Ontario also having several strong tornadoes. Just a week later, the Midwest would see record cold temperatures, slowing recovery efforts.

Meteorological history
In late November, a unusually late season heat wave impacted the Midwestern United States, Indianapolis saw a record high for that month of 90 degrees, shattering the previous record high of 79 degrees there by 11 degrees. This left a unstable environment in that region. Meanwhile, a late season storm in the Pacific's remnants made landfall in the northwest, and soon it's remnants emerged into a frontal system. As the frontal system would interact with favorable conditions for severe weather, particularly temperatures upwards of 75°F in parts of South Dakota, severe thunderstorms developed on November 30. The SPC had already issued a Day 2 Moderate Risk for much of the lower Great Lakes and upper Midwest, as well as a Day 1 Enhanced Risk in the Dakotas. As the storms moved southeast, on December 1, the SPC issued a High Risk for northern Illinois and Indiana, as strong wind shear, warm temperatures, high dew points and the frontal system were forecast to combine to form a potentially dangerous tornado outbreak. Supercells would develop late that morning, and move through the High Risk area. In total, 102 of the 131 tornadoes touched down on December 1, making it the most active tornado day ever recorded in the month of December. As the system moved northeast, a Enhanced Risk was issued on December 2 for much of Indiana, Ohio and Michigan, with Environment Canada issuing a tornado watch for southern Ontario, another 17 tornadoes would touch down that day, including a EF4 in Coldwater, Michigan, which would kill 28 people. As well as a EF4 in Windsor, Ontario, which would kill 2 people. On December 3, a Slight Risk was issued for northern Ohio and northern Pennsylvania, as well as a tornado watch for southern Ontario. 12 more tornadoes would touch down on December 3, including a EF3 near Erie, Pennsylvania. The storms would enter a less favorable atmosphere, limiting severe activity on December 4 to sporadic large hail and damaging wind events across the northeast, and the storm moved off shore on December 5.

Freeport, Illinois
As severe thunderstorms tracked through a favorable environment across northern Illinois, one of the cells developed strong rotation around 11:30 am on December 1 near Freeport, Illinois, a funnel cloud was reported at 11:36 am, and a tornado touched down at 11:38 am. The tornado quickly tracked southeast towards Freeport as a EF1, and began intensifying, EF2 damage was first documented just northwest of Freeport, with a time estimated around 11:45 am. It then moved into Freeport as a high-end EF2, before intensifying into a low-end EF3 as it moved through the center of Freeport, prompting a tornado emergency. The tornado would have several documented areas of potential EF4 damage as it moved through southeast Freeport, the tornado would lift at 12:04 pm as the storm weakened.

Shabbona, Illinois
As the supercell that had previously produced the Freeport tornado re-intensified, it produced another funnel cloud at 12:51 pm about 8 miles west of Shabbona, by this time the storm had stuck to a east southeast. At 12:56 pm, a tornado touchdown was confirmed 6 miles west of Shabbona.

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