Weekend severe weather threat to include potential for tornadoes in central, southern US
By Alex Sosnowski, AccuWeather senior meteorologist
March 08, 2019, 9:45:07 AM EST
The anticipated severe thunderstorm outbreak includes the potential for a few tornadoes over the middle and lower Mississippi Valley on Saturday.
"The full spectrum of severe weather is anticipated, ranging from damaging wind gusts, large hail and frequent lightning strikes to flash flooding and tornadoes," according to AccuWeather Storm Warning Meteorologist Kayla St. Germain.
"The greatest period of concern is from early Saturday afternoon into Saturday night," St. Germain said.
The first big storms during the outbreak are likely to erupt from northeastern Texas to eastern Oklahoma, southeastern Kansas, Missouri, Arkansas and Louisiana, as well as over the lower part of the Ohio Valley.
There may be isolated severe storms that erupt southeast of this area over parts of the lower Mississippi and Tennessee valleys prior to the general area of thunderstorms forming a solid line and advancing southeastward late in the day and at night.
Where individual thunderstorms form ahead of a press of cooler and less humid air, the risk of strong, long-lasting tornadoes may be greatest.
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In addition to the main severe weather day on Saturday, a few heavy to locally severe storms may erupt on Friday night over portions of Oklahoma and central Texas. Heavy, gusty and locally severe storms may progress into the southeastern corner of the nation on Sunday as well.
So far this year, storm systems have shown significantly more virility in terms of severe weather than in 2018.
"The EF4 tornado in Beauregard, Alabama, this past Sunday was rated stronger than any tornado last year," according to AccuWeather Meteorologist Jesse Ferrell.
"Following a record low number of fatalities (10) from 2018, there have already been 23 fatalities this year," Ferrell said. "All the fatalities so far this year occurred during the outbreak on Sunday."
However, it is not so much that this year is off to an extraordinary start in terms of severe thunderstorms and tornadoes, but rather that last year brought remarkably low numbers.
"Last year, we had a broad area of chilly air that stuck around well into the spring over the South Central and Southeastern states," according to AccuWeather Lead Long-Range Meteorologist Paul Pastelok.
The persistent chill stifled severe thunderstorm formation.
"During a typical March, we tend to have a strong jet stream lingering over the South, while at the same time, we get significant warming from the more direct sun angle," Pastelok said.
AccuWeather meteorologists expect the setup this weekend to follow along the more typical route for March.
While chilly air recently invaded the region, it is expected to retreat enough to allow thunderstorms to trend severe as the big storm develops over the Great Plains.
How efficiently the big storm is able to pull the warm air northward may determine the amount and magnitude of severe weather.
Sunshine is often a trigger for violent thunderstorms. Should the sun break out for a few hours, the risk of severe thunderstorms is likely to increase.
While the overall magnitude of the upcoming severe weather event has yet to be determined, there are some necessary ingredients for severe thunderstorms and tornadoes that are likely to come together.
These include a surge of warm and humid air, as well as strengthening upper-level winds that vary in direction with increasing height in the atmosphere, or wind shear.
It is the wind shear that can cause thunderstorms to rotate and, in some cases, help to spin up a tornado.
AccuWeather will continue to provide updates on the intensity, nature, coverage and timing of the severe weather in the coming days.
Download the free AccuWeather app for the latest forecast and to receive severe weather watches and warnings as they are issued.
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