Severe weather pummels U.S. Midwest and South, 21 dead

Severe thunderstorm warnings and tornado warnings, as of late in the day on March 31, 2023 … A tornado “warning” means a tornado has been sighted or indicated by weather radar, and there is imminent danger to life and property.

Tornadoes hit U.S. Midwest and South is reporting 21 deaths so far this afternoon, after storms raked the U.S. Midwest and South on Friday:

Half of those deaths were in Arkansas, while three people died in Illinois and two were killed in Indiana.

As of 11 UTC (6 a.m. CDT) on April 1, the National Weather Service’s NWS Tornado feed on Twitter – used to distribute experimental tornado warning impact graphics – was still issuing storm warnings. One of the worst-hit places on Friday was around Little Rock, Arkansas. Officials had reported more than 600 injuries by Friday night. Twin tornadoes hit in Iowa, and tornadoes also affected Mississippi, Illinois, Wisconsin, Indiana and Tennessee. In Belvidere, Illinois, severe weather struck the Apollo Theater during a concert, collapsing a portion of the roof.

Weather Channel completed coverage is here

Chart showing tornadoes in 2023 in contrast to the past 7 decades.
View larger. | According to U.S. Storm Prediction Center data, Prior to the March 31, 2023 outbreak, in terms of U.S. tornadoes, 2023 was the third-most-active start to a year on record in the U.S. The record goes back about 7 decades.

Arkansas tornadoes

Iowa tornadoes

Earlier forecast for the severe weather outbreak

Another round of severe weather is targeting the central United States, just a week after the last deadly tornado outbreak. Experts expect severe weather from Iowa to Mississippi on Friday evening. Storms will bring the threat of significant tornadoes, damaging wind and very large hail to millions of people.

Around Friday 11:30 a.m. CDT, the Storm Prediction Center issued a rare “high risk” for severe storms in parts of the central U.S. It also expects a widespread potential for “Strong and potentially violent long-tracked tornadoes” across the moderate risk area. Strong tornadoes are EF-2 or higher, and violent tornadoes are EF-4 strength or higher. The NWS definition for high risk is:

An area where a severe weather outbreak is expected from either numerous intense and long-tracked tornadoes or a long-lived derecho-producing thunderstorm complex that produces hurricane-force wind gusts and widespread damage. This risk is reserved for when high confidence exists in widespread coverage of severe weather with embedded instances of extreme severe (i.e., violent tornadoes or very damaging convective wind events).

Map of US with some areas in pink indicating high risk of severe weather.
Around 11:30 a.m. CDT on March 31, 2023, the National Weather Service issued a rare “high risk” alert for severe weather in the parts of the central United States. It calls for a severe weather outbreak of intense and widespread severe thunderstorms – including tornadoes, hurricane-force winds and hail – Friday afternoon and into the overnight hours. Image via NWS Storm Prediction Center.

Parts of Illinois, Iowa, Arkansas and Mississippi face the greatest threat in the high-risk region. But a large region is also under moderate risk of severe storms. A region of moderate risk is where locals can expect long-tracked tornadoes and widespread damaging winds. Straight line winds in the storms may exceed hurricane force (greater than 74 mph).

Forecasters also expect strong storms and tornadoes across a very wide range from central Iowa to northeastern Texas and northern Alabama with a linear storm mode through the evening and overnight hours. The forecast remains more uncertain for those regions.

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Severe weather outbreak in the Midwest

The Storm Prediction center expect supercells to form mid-afternoon in central Iowa, close to the center of a very large low-pressure system over the Midwest. Supercells are rotating thunderstorms that produce all types of severe weather. The supercells in Iowa will initially produce large hail, possibly in excess of two inches. They may also produce tornadoes within a few minutes or hours of forming. Storms in this area may move as fast as 80 mph.

The supercells will gradually merge together through the evening and create a line of storms further east into Illinois. The primary hazard with this line of storms will be strong straight-line winds, although brief tornadoes may still be possible. The storms will likely make it to the Chicago area after sunset.

Severe weather outbreak in the mid-South

The second threat area is primarily focused around northeastern Arkansas. Although all the storms will be a part of the same storm system, the conditions in Arkansas will be much different than those in Iowa. Large supercells with flooding rains will develop in the afternoon. Due to strong wind shear in this area, the storms will be capable of producing significant and long-track tornadoes through sunset.

Snow, wind and fire

The deep low pressure over the Midwest will produce more than just severe weather. Forecasters expect very strong winds on the back end of the system. A combination of these winds and dry air will lead to enhanced fire weather conditions over the High Plains through Friday and Saturday. The system will likely also drop heavy snowfall over the Upper Midwest. Parts of Minnesota and Wisconsin will see one to two feet of snow through Saturday.

Seasonal severe weather

This severe weather is just one set of storms in a long string of severe weather across the central U.S., driven by deep troughs in the jet stream that commonly occur in March and April. A tornado outbreak one week ago produced multiple long-track tornadoes in Mississippi, including an EF-4 that killed 26 people.

More severe weather to come

Conditions for severe weather become more favorable throughout the spring. Warmer temperatures and higher moisture are key for severe-weather development. These components will increase through April and May. In fact, another severe weather event looks likely on Tuesday, according to a long-range forecast by the Storm Prediction Center. Climatology shows that this kind of frequency from severe weather is normal for March and April and is expected to peak in mid-May.

Map of the US with shades of orange showing darkest color over Oklahoma but extending all the way east.
Climatology of where severe weather is most likely in mid-May, per the Storm Prediction Center. Image via NOAA.

Bottom line: Severe weather and tornadoes pummeled the central United States, and into the South, on Friday, March 31, 2023. Images and video here.

Read more: Tornado outbreak kills 26 in Mississippi

April 1, 2023

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