After a remarkably quiet start to the severe weather season in the USA -- which included the fewest number of tornadoes in March in several decades -- signs are pointing to a more active pattern for April.
This includes the possibility of an outbreak this week in the central USA.
This week's severe weather outbreak "is likely to be the worst of the season so far," AccuWeather meteorologist Alex Sosnowski says, with the greatest threat Tuesday in the central and southern Plains, and Wednesday in the mid- to lower Mississippi Valley.
An online report from the Storm Prediction Center (SPC) in Norman, Okla., warns of "a setup favorable for potentially significant and widespread severe weather" on Tuesday and Wednesday. The center says that the cities of Dallas, Oklahoma City and Kansas City, Mo., are most at risk Tuesday, and that St. Louis and Memphis are at greatest risk for severe thunderstorms on Wednesday.
Meteorologists define severe thunderstorms as any thunderstorm that produces either tornadoes, hail of at least one inch in diameter, and/or wind gusts of 58 mph or greater.
The severe weather threat this week will likely only be a preview of coming attractions, as the typical peak of severe weather season -- from mid-April through May -- approaches: "The Deep South is going to be under the gun during April," AccuWeather meteorologist Dan Kottlowski says.
During the heart of the severe season, when the threat of tornadoes is usually at its highest, AccuWeather reports that areas to watch will be the lower Mississippi, Ohio and Tennessee valleys. Little Rock, Memphis and Nashville are among the cities that lie in the zone of greatest risk for severe weather throughout the spring.
The SPC reports that so far this year, according to preliminary data through April 4, there have been only 155 reports of tornadoes across the country, which is far below the average of 286.
March was especially quiet, due primarily to the cold air that kept severe weather at bay: Only 17 tornadoes were tallied across the nation in March 2013, according to Weather Channel severe weather expert Greg Forbes.
If this preliminary total holds up, Forbes says, this would be the lowest U.S. tornado count for the month of March in 35 years -- since March 1978 when only 17 tornadoes were counted.
The most recent March with a lower U.S. tornado tally was 1969, with only eight tornadoes. An average March sees 98 tornadoes in the USA. Last March, there were 154 tornadoes and 43 deaths, Forbes says.
So far this year, only two people have been killed by tornadoes, the SPC reports: one in January and one in February.
Tornadoes and severe storms continue to be one of the nation's top weather phenomena in terms of economic damage: A recent report from insurance firm Lloyd's of London found that annual losses from severe thunderstorms -- including tornadoes -- account for more than half of all U.S. catastrophe losses since 1990.
"The U.S. experiences more tornadoes than any other country in the world," according to the report. "Every year an average of 1,200 tornadoes kill up to 60 people, injure 1,500 and cause at least $400 million in economic damage in the U.S."
The report shows how tornadoes have become a rising risk in the USA due mainly to urbanization: "As populations have increased, so has urban sprawl, and fewer areas remain completely unpopulated," the Lloyd's report says.
And although the number of tornado reports has increased by an average of 14 per year since the mid-50s, "a large proportion of this can be attributed to population movement to rural areas and increased communication around and understanding of the nature of tornadoes."
Doyle Rice, USA TODAY