Tornado Digest: Major outbreak to close April, and the first May threat mid-week

EF-4 Vilonia, AR tornado. (Virginia Millwood via Twitter)

EF-4 Vilonia, AR tornado. (Virginia Millwood via Twitter)

Looking back at the week of April 27-May 3, and a brief look ahead.

After a very quiet April, tornadoes — including the first two violent EF4s of the year — ravaged parts of the southern United States to close the month.

Two days in a row featured “high risks” from the Storm Prediction Center, something that only happens every other year or so.

When all was done, roughly 75 or more tornadoes touched down in one of the more active events over the past few years. Among those numbers, at least five killer tornadoes touched down in Arkansas, Mississippi, Alabama and Tennessee.

Tornado activity across the U.S. April 27-May3. Note: A tornado briefly touched down in Washington state and is not shown.

Tornado activity across the U.S. April 27-May3. Note: A tornado briefly touched down in Washington state and is not shown.

Related: Videos from the late April 2014 tornado outbreaks

April 27 – Eastern Plains and the Mid South

The week begin with the start of several days of tornado activity across the southern United States as a strong upper-level trough cutoff from the steering flow and continued to send waves of severe weather episodes across the region. On Sunday the 27th, tornado activity was not terribly widespread, with only about a dozen observed. What lacked in numbers was made up in intensity. One EF4 plowed through Mayflower and Vilonia, Arkansas among other spots to the northwest of Little Rock. 15 were left dead in the event.

Related: NWS Little Rock tornado surveys for April 27

April 28 – Mid South

The second high risk day in a row, this time shifted a bit to the southeast. When it comes to a traditional tornado outbreak featuring a handful or more supercells almost all dropping tornadoes, this was it. Though much smaller in scale than the April 27, 2011 outbreak, some of the same areas were hit. Over 40 tornadoes have been confirmed in Mississippi and Alabama alone, including an EF4 in Winston County, MS. Four more killer tornadoes occurred on this day, with another 15 people lost.

Related: NWS Jackson MS info | NWS Birgmingham AL info | NWS Huntsville AL info | NWS Memphis TN info

April 29 – Southeast

Tornadic storms were mainly confined to North Carolina on this day, and overall the threat materialized on the low end of potential which was a good thing given what already happened with this system. Several brief and weak tornadoes touched down in NC, and also down in the Florida panhandle. A cold-core tornado was confirmed in Illinois.

April 30 – Mid-Atlantic

Some tornado risk was expected to continue into the mid-Atlantic to close the month, and there was a tornado watch issued for parts of North Carolina and Virginia. The story of the day was mainly flooding and continual rain, which partly helped keep things from bubbling too much with atmospheric stability over a good chunk of the region.

Another trough mid-week

The last storm system mostly wiped the country clean of moisture, and storms have been few and far between since.

But, it’s May, and that means we’re into the average peak of the tornado year. No gigantic systems are in the offing, though an energetic mid-level trough should push out into the central U.S. during the week. Once it does, at least some severe weather is likely. And it’s hard to get a system with no tornadoes in May…

May 5 0z GFS 500mb height and vorticity shows a trough about to eject into the Plains late Wednesday. (Weatherbell.com)

May 5 0z GFS 500mb height and vorticity shows a trough about to eject into the Plains late Wednesday. (Weatherbell.com)

As of now, there are some timing issues for both days with the best look on this system. It’s a little slow to move into the Plains for a big day on Wednesday and a little fast for Thursday. It does not appear this will be a major tornado outbreak, but perhaps the zone most at risk lies from the eastern Plains into the Midwest.

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Defense and foreign policy researcher at a D.C. think tank. Information lead for the Washington Post's Capital Weather Gang.