Great Blue Norther of November 11, 1911

On Saturday, November 11, 1911, a cold snap, known as the Great Blue Norther of 11/11/11, affected the Central United States. Many cities broke record highs, going into the 70s and 80s early that afternoon. By nightfall, cities were dealing with temperatures in the teens and single-digits on the Fahrenheit scale. This is the only day in many midwest cities' weather bureau jurisdictions where the record highs and lows were broken for the same day. Some cities experienced tornadoes on Saturday and a blizzard on Sunday. A blizzard even occurred within one hour after an F4 tornado hit Rock County, Wisconsin.

The front produced severe weather and tornadoes across the upper Mississippi Valley, a blizzard in Ohio, and the windy conditions upon front passage caused a dust storm in Oklahoma. Alongside the dramatic temperature swings, the cold front brought a destructive tornado outbreak to parts of the Midwest. At least 13 tornadoes touched down across five states as the system moved through, resulting in 13 fatalities. Hundreds of structures were destroyed by the storms and many areas had to conduct search and rescue missions amidst blizzard conditions. According to Thomas P. Grazulis, this outbreak was one of the worst on record in November for the north-central States.

Background
The main cause of such a dramatic cold snap was an extremely strong storm system separating warm, humid air from frigid, arctic air. Dramatic cold snaps tend to occur mostly in the month of November, though they can also come in February or March. These arrivals of Continental Polar or Arctic air masses are generally called northers, and the one in question was marked by a mass of steel blue clouds in the vicinity of the surface front, hence the name. Although temperature drops of this extent have happened on other occasions, as recently as February 2009, the fact that the 1911 cold front passage was during the autumn and came after such warm weather contributed to the properties mentioned in this article.

Impact
The cold front was so strong, that while several states saw record monthly highs on November 10 and 11, they saw record cold monthly lows on November 12 and 13. This was especially true in Missouri, where one station had a high of 93 F before the storm, and after the storm, another station had a low of -3 F. The cold front began on November 9. Rapid City, South Dakota went from 55 F at 6am to 3 F at 8am. Between November 10 and 11th, Denver experienced its eleventh largest two day temperature swing, from 66 to -2 F, which is a 68 F-change change.

On November 11, temperatures in Kansas City had reached a record high of 76 F by late morning before the front moved through. As the cold front approached, the winds increased turning from southeast to northwest. By midnight, the temperature had dropped to 11 F, a 65 F-change difference in 14 hours. The next day would have a record low of 6 F and a high of only 21 F. In Springfield, the temperature difference was even more extreme. Springfield was at 80 °F at about 3:45 p.m. CST (21:45 UTC), before the cold front moved through. Fifteen minutes later, the temperature was at 40 F with winds out of the northwest at 40 mi/h. By 7:00 p.m. CST (01:00 UTC 12 November) the temperature had dropped a further 20 F, and by midnight (06:00 UTC), a record low of 13 F was established. It was the first time since records had been kept for Springfield when the record high and record low were broken in the same day. The freak temperature difference was also a record breaker: 67 F-change in 10 hours. Peak wind gusts reached 74 mph. The low on the morning of November 12 was 9 F. St. Louis dropped from 74 to 49 F in just ten minutes. Record highs and lows were established on the same day in Oklahoma City as well with a high of 83 °F and low of 17 °F; temperature difference: 66 F-change. Both records still hold. The temperate dropped further to a record low of 14 F on November 12, before gradually warming, as Oklahoma City hit 68 F on November 13 and 74 F on November 14. It also produced a dust storm. Tulsa, Oklahoma had an even more dramatic plunge from 85 F in the afternoon of November 11 to 15 F by the morning of November 12, although the temperature at midnight is not known. Independence, Kansas saw the temperature drop 50 F-change from 83 to 33 F in one hour. In Denton, Texas, the temperature drop wasn't as immediate, with it dropping from 85 F at 5pm to 68 F by 6pm, but the low the morning of November 12 was still 22 F. While this wasn't Amarillo's biggest temperature drop, the drop from 70 to 13 F is still an impressive 57 F-change drop. Nearby Dallas also saw an impressive plunge from 85 to 39 F by midnight and by the next morning the mercury was 21 F. In Chicago, Illinois, people died separately of heatstroke and cold, respectively, within 24 hours, the first such incidence on record in the city. They dropped from 74 to 13 F during the event. Across central Illinois, up to 1 in of snow fell, and in Peoria, Illinois, after a high of 77 F on November 11, the temperature crashed to 17 F by midnight, and the high on November 12 was 18 F. While only the southern and eastern parts of Iowa felt the Norther, the impacts there were nonetheless powerful, as Albia, Iowa fell from 72 to 5 F in twelve hours.

The front did not reach Columbus until 3am on November 12, but when it did, temperatures plummeted from 70 F, just a degree from a record high, to 49 F in an hour, and down to 16 F - a record low - that night. By November 13, temperatures dipped further to 14 F. Lexington, KY also saw the temperature drop on the 12th, when it went from nearly 70 F down to a record low from 14 F. It dipped to another record low of 13 F on November 13, and a record cold high of 28 F was also established. However, the record low for November 13 was broken in 2019. Bowling Green saw the drop across the entire day on November 12, from 75 to 22 F. In New York City, the swing was not quite as extreme, but still fell from 69 F in the afternoon to 33 F at midnight, and slipped to a record low (at that time) the next morning of 26 F. Temperature plunges ranged from 42 to 54 F-change on the East Coast. Besides the East Coast, San Antonio was also spared, with a temperature drop of only 35 F-change.

Tornadoes
On Saturday, November 11, 1911, a regionally and seasonally significant tornado outbreak affected the Great Lakes region of the United States. The outbreak generated at least 13 tornadoes, including a violent, long-tracked F4 that impacted Wisconsin, killing at least nine people and injuring 50 more. Other intense tornadoes occurred in Illinois and Indiana, resulting in four additional fatalities. Several other tornadoes were reported from multiple states. In all, the outbreak killed 16 people and injured at least 101. Total losses exceeded $1.755 million (1911 USD). Tornado researcher Thomas P. Grazulis considered the outbreak to be the worst in the month of November on record at the time in the Great Lakes region.

Some cities experienced tornadoes on Saturday and a blizzard on Sunday. The passage of a cold front, marked by strong winds, produced severe weather, including tornadoes, across the upper Mississippi River Valley, a blizzard in Ohio, and a dust storm in Oklahoma.

Confirmed tornadoes

 * A possible tornado caused extensive damage in Bedford, Lawrence County, Indiana, with losses reaching $500,000. Another possible tornado killed horses and cattle near Kingsland in Eaton County, Michigan. At least three other tornadoes may have affected Green, Dane, and Walworth counties, respectively, in the state of Wisconsin.