Forecasters are monitoring several storm systems that will chug across the country through the upcoming week, as the weather makers may help to set the stage for a potentially violent severe weather outbreak during the middle to latter part of the week.
Several of the ingredients necessary for severe weather to erupt are lined up when the jet stream moves southward as it is expected to do this week. For one, a southward dive in the jet steam allows storms to tap into moisture from the Gulf of Mexico.
Additionally, cold air often plunges in from the north when the jet stream jogs south. The clash of cold air to the north with warm, moist air from the Gulf increases the chance of damaging thunderstorms to ignite, and the violent collision can create severe weather outbreaks that last several days.
The exact positioning of the jet stream will determine the zone most likely to experience severe weather late week. At this time, locations from central Texas to the Ohio Valley are being put on alert for the potential for severe weather.
Cities like Dallas, Oklahoma City, Memphis, St. Louis and Indianapolis are all included in this zone. Additionally, thunderstorms could move through portions of many major interstates, including interstates 20, 30, 40, 55 and 70.
Even though the storm system could trigger several days of severe weather, it is expected to move through the central and eastern United States quickly enough that most point locations may only be threatened by severe thunderstorms for a 12- to 24-hour time period.
AccuWeather meteorologists warn that the threats of severe thunderstorms could linger during the dark, overnight hours for some areas, adding to the dangers.
In this kind of a setup, thunderstorms can produce heavy downpours and flash flooding and can dangerously reduce the visibility for motorists.
The strongest storms may also be capable of producing damaging wind gusts and tornadoes, according to AccuWeather forecasters. Even outside of the most volatile storms that develop, frequent lightning could pose a threat to those outdoors.
Additional rounds of violent thunderstorms are likely to follow, especially as the season changes over to spring and the typical peak for severe weather approaches in the U.S.
"Without a change in the pattern, the same setup could repeat itself several times during the second half of March," AccuWeather Senior Meteorologist Alex Sosnowski said, adding that the bull's-eye for severe weather will be a moving target with each subsequent threat. Portions of the mid-Atlantic and Southeast will need to watch as thunderstorms press eastward late week.
The United States has already experienced more tornadoes than normal for the year to date, with 140 reported as of March 11, according to NOAA's Storm Prediction Center (SPC). AccuWeather meteorologists cite unseasonably warm conditions as the culprit behind the well above-average tornado numbers.
Ninety preliminary tornado reports occurred in January, 51 in February and 22 so far in March.
Jan. 11 was the busiest day thus far in 2020 with a total of 557 severe weather reports, followed by Jan. 10 with 295, Feb. 6 with 189, Feb. 7 with 124 and Feb. 5 with 116.
A man looks over buildings destroyed by storms Tuesday, March 3, 2020, in Nashville, Tenn. Tornadoes ripped across Tennessee early Tuesday, shredding buildings and killing multiple people. (AP Photo/Mark Humphrey)
Deadly tornadoes ripped across Tennessee on March 3. The most violent tornado to strike the Nashville area in approximately 11 years was rated as an EF4 by the National Weather Service (NWS). The twister, which struck Putnam County, likely packed winds as high as 175 mph, according to the NWS office in Nashville. The SPC listed a total of 100 severe weather reports across the U.S. that day, which made it come in at no. 6 in terms of most active days this year.
In AccuWeather's annual tornado forecast, released back on Feb. 20, long-range forecasters predicted a normal to slightly above-normal number of tornadoes in 2020 with a range of 1,350 to 1,450. That range is close to what occurred in 2019 and 5 to 15 percent more than the U.S. annual average.
AccuWeather Lead Long-Range Meteorologist Paul Pastelok first warned in the February annual outlook that "once the cold snap lifts out in the central Plains and lower Midwest by mid-March, things could get unstable quickly and we could have another active area there."
More than double the average number of tornadoes is predicted in March, a typical total in April and roughly 10 to 30 percent more tornadoes than average in May. There are an average of 75 tornadoes in March, 178 in April and 269 in May, according to SPC records from 1991-2015.
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