Great Blue Norther of November 11, 1911

On Saturday, November 11, 1911, a cold snap, known as the Great Blue Norther or 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 12 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 before the storm, and after the storm, another station had a low of . The cold front began on November 9. Rapid City, South Dakota went from at 6am to at 8am. Between November 10 and 11th, Denver experienced its eleventh largest two day temperature swing, from to , which is a 68°F (38°C) change.
On November 11, temperatures in Kansas City had reached a record high of 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 , a 65°F (36°C) difference in 14 hours. The next day would have a record low of and a high of only . In Springfield, the temperature difference was even more extreme. Springfield was at at about 3:45 p.m. CST (21:45 UTC), before the cold front moved through. Fifteen minutes later, the temperature was at with winds out of the northwest at . By 7:00 p.m. CST (01:00 UTC 12 November) the temperature had dropped a further , and by midnight (06:00 UTC), a record low of 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 (37°C) in 10 hours. Peak wind gusts reached . The low on the morning of November 12 was . St. Louis dropped from to in just ten minutes. Record highs and lows were established on the same day in Oklahoma City as well with a high of and low of ; temperature difference: 66°F (36°C). Both records still hold. The temperate dropped further to a record low of on November 12, before gradually warming, as Oklahoma City hit on November 13 and on November 14. It also produced a dust storm. Tulsa, Oklahoma had an even more dramatic plunge from in the afternoon of November 11 to by the morning of November 12, although the temperature at midnight is not known. Independence, Kansas saw the temperature drop 50°F (28°C) from to in one hour. In Denton, Texas, the temperature drop wasn’t as immediate, with it dropping from at 5pm to by 6pm, but the low the morning of November 12 was still . While this wasn’t Amarillo’s biggest temperature drop, the drop from to is still an impressive 57°F (32°C) drop. Nearby Dallas also saw an impressive plunge from to by midnight and by the next morning the mercury was . 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 to during the event. Across central Illinois, up to of snow fell, and in Peoria, Illinois, after a high of on November 11, the temperature crashed to by midnight, and the high on November 12 was . While only the southern and eastern parts of Iowa felt the Norther, the impacts there were nonetheless powerful, as Albia, Iowa fell from to in twelve hours.
The front did not reach Columbus until 3am on November 12, but when it did, temperatures plummeted from , just a degree from a record high, to in an hour, and down to - a record low - that night. By November 13, temperatures dipped further to . Lexington, KY also saw the temperature drop on the 12th, when it went from nearly down to a record low from . It dipped to another record low of on November 13, and a record cold high of 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 to . In New York City, the swing was not quite as extreme, but still fell from in the afternoon to at midnight, and slipped to a record low (at that time) the next morning of . Temperature plunges ranged from 42°F to 54°F (23°C to 30°C) on the East Coast. Besides the East Coast, San Antonio was also spared, with a temperature drop of only 35°F (19°C).
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.