By Gilles MATRICON, meteorologist
–
–
A depression deepened over Texas on Saturday before intensifying as it moved up to the northeastern states. It thus affects all of eastern and northern United States until Tuesday morning. Tornadoes, stormy winds, intense rain and blizzard affect more than 100 million Americans. This storm was followed by a remarkable winter offensive until the weekend.
A low pressure system was created Saturday in Texas, drawing cold air from northern Canada to the Rockies. At the same time, very hot and unstable air was rising from the Gulf of Mexico to the eastern United States. These two air masses came into conflict, with consequences of powerful thunderstorms from Texas to Mississippi which reach Alabama, Iowa as well as the 2 Carolines and all the Atlantic coast of the country. This situation favors such powerful generalized thunderstorms no longer met since April 2018.
Worrisome setting, jet stream. This powerful high altitude wind is in phase with this conflict of air masses. Thunderstorms are all the more violent, with extreme phenomena such as heavy downpours, violent gusts of wind, hailstorms, flash floods and an “outbreak” of tornadoes (large number of tornadoes in a very short time).
More than half of the United States affected
After hitting the Great Plains, the most severe thunderstorms affected the entire northeastern United States on Monday, over 4000 km long and wide, which is exceptionall. Mardi, these rains and thunderstorms will sweep Maine up towards Pennsylvania.
Tornado outbreak
The Great American Plains suffered severe thunderstorms with numerous tornadoes until Monday evening. 34 tornadoes have been reported since Saturday evening in Texas, Louisiana, Mississippi and Georgia.
A #tornado crossed a neighborhood in the city of sunday morning #Monroe in #Louisiana, severely damaging many homes. https://t.co/jPcGwKaJex
– The Weather Channel (@lachainemeteo) April 12, 2020
A very heavy human toll
In the state of Mississippi, several tornadoes touched down, killing 11 people. The material damage is very heavy. In all, 18 people died in these bad weather.
In the United States, the passage of several #tornadoes in Mississippi State on Sunday left at least 11 people dead. https://t.co/g3zGlbwP6t
– The Weather Channel (@lachainemeteo) April 13, 2020
Heavy rain, hailstorms and floods
The states of Arkansas, Alabama, Missouri, Louisiana, Mississippi, Tennessee, Kentucky, the 2 Carolinas and the Virginias experience heavy rain. Locally, it can fall between 150 and 200 mm of rain in 24 hours between Atlanta, Nashville, Memphis and Charlotte, the equivalent of a month of rain. These rains cause the tributaries of the Mississippi River to rise very rapidly. The rivers descending from the Appalachians also react with some floods and floods.
Video of an impressive hailstorm Saturday at #Texas. Of # hail the size of tennis balls burst the windshield of a thunderstorm hunter’s car! https://t.co/tWDdwahO6n
– The Weather Channel (@lachainemeteo) April 13, 2020
Heavy snowfall in the Great Lakes region
This particularly deep depression (970 hPa) causes in its northern part, where the cold air turns down, snowfall in the Great Lakes region, between Wisconsin, northern Illinois, Indiana, Ohio and northern Michigan on Monday. Locally, heavy, sticky snow may fall 10 to 20 cm.
Strong and stormy winds, gusts over 100 km / h
The depression responsible for these bad weather has the characteristics of a winter storm with a pressure value in its center of 970 hPa. It is accompanied by strong winds of up to 90 to 100 km / h over the Great Lakes region, and up to 120 km / h on Monday in the Appalachian mountains. Then, between Monday evening and Tuesday afternoon, it is all the northeast of the United States which is swept by this storm with gusts which can reach 110 km / h between Pennsylvania and Maine, from Boston to New -York.
Quebec was also impacted Tuesday by winds at 100 km / h and heavy snowfall north of Montreal, Toronto and Quebec.
After the bad weather, an exceptional cold for the season is developing
Until Friday, 3/4 of the United States suffer very cold weather for the season due to the descent of a polar air mass. Jellies are becoming widespread. Only the states bordering the Gulf of Mexico and Florida escape frost. Everywhere else, the nights promise to be very cold with sometimes severe frosts with -5 ° C in Chicago for example.
–
