A “cold core” setup under an upper low spawned low-topped supercells in Kansas on May 21, 2019. Some were tornadic, but not this one. (Ian Livingston/The Washington Post)

A flare-up of severe weather is expected across parts of the central and eastern Lower 48 from mid- to late March, with an above-average risk of severe thunderstorms capable of producing damaging winds, large hail and tornadoes.

From the eastern Plains to parts of the Tennessee and Mississippi valleys, a flurry of thunderstorm activity is possible should the pieces fall into place amid a favorable pattern for severe storms, according to forecasters. This zone includes parts of Tennessee, still reeling from last week’s deadly tornado event.

The jump-start to storminess is likely to carry on into April, which is typically the beginning of the peak of the severe weather season, which continues through May and into June. In other words, the potential exists for an extended severe storm season in some areas.

Where


The Climate Prediction Center outlines different hazards that may brew up in the next two weeks. (NOAA/CPC)

Storminess looks to hop into overdrive by the middle of the month, most likely around March 16 onward. A stormy pattern is possible over a large stretch of real estate, targeting portions of the western Tennessee Valley, the Ozarks, much of the lower Mississippi Valley, and the central and southern Plains — especially east of Interstate 35.

Depending on the evolution of weather patterns, western extremities of the Ohio Valley into the Corn Belt could come into play as well.

Multiple rounds of heavy rain associated with the storms could bring flood concerns across Dixie Alley.

“Flooding along major rivers across parts of the Southeast and lower Mississippi Valley is expected to continue through at least mid-March,” wrote the Climate Prediction Center.

Victor Gensini, a professor at Northern Illinois University, also published a map of where he expects potential severe weather to strike in the coming weeks:

Gensini and his team exhibited considerable skill in predicting the May 2019 tornado barrage several weeks in advance.

When


Green skies and rotating clouds herald the arrival of a tornado-warned hail-laden supercell thunderstorm south of Matador, Tex., on May 24, 2019. (Matthew Cappucci)

The most active period favoring an increased threat of strong to severe thunderstorms looks to be from about March 16 to 23, with uncertainty thereafter. However, there are signs that point to continued storm chances before a period of enhanced storminess as the calendar flips to April.

There’s also a marginal risk of severe thunderstorms in the coming days, centered mainly over the Ozark Plateau, according to the National Weather Service Storm Prediction Center.

“Based on model consensus, there are two distinct periods with a severe weather risk,” Brad Pugh of the National Weather Service’s Climate Prediction Center wrote in an online outlook. “Prior to [March 13] and then again from March 16 to 20.”

Beyond that, it’s impossible to make specific predictions. It’s worth noting that April, May and June are historically the most active months for significant severe thunderstorms, including tornadoes.

Why


The longer-range American CFS model displays frigid air at the mid-levels of the atmosphere over the west, with a surge of high pressure and milder air building into the east. This is for the week of March 16 to 23. (Tropical Tidbits)

To brew severe thunderstorms, two main ingredients are necessary: energy for lift in the atmosphere, derived from a supply of warm, moisture-rich air, and the wind dynamics needed for storms to rotate.

Once these two ingredients overlap, storms ordinarily need a trigger to erupt. This triggering mechanism is usually an approaching cold air mass.

Predicting individual bouts of storminess or specific severe weather events is impossible more than about seven to nine days in advance; only at shorter time ranges can a forecaster key into smaller-scale features that govern thunderstorm behavior. But even up to two or three weeks in advance, we can sometimes spot the larger-scale precursors to storminess.


A supercell thunderstorm whirls ominously near McCook, Neb., on May 17, 2019, shortly before producing a series of tornadoes. (Matthew Cappucci)

Among these? Low pressure in the western United States with a ridge of high pressure building in over the east. That clockwise-spinning high in the east will bring southerly winds on its western periphery, drawing a strip of springlike mildness and Gulf of Mexico humidity north over parts of the Deep South and perhaps the Tennessee and Mississippi valleys.

Meanwhile, turrets of upper-atmospheric chilliness will eject out of the sprawling low-pressure area banked up in the Rockies. Any one of those may trigger its own wave of storms.

The period is unlikely to produce constant storminess or even predominantly stormy conditions; instead, above-average warmth in the South and Southeast will be punctuated by occasional chances of severe weather.

Each storm system could drag with it sufficient wind energy at the upper levels to stir up rotating storms, the disturbances themselves nestled in southward meanders of the jet stream. The jet stream is a river of swiftly moving winds in the upper atmosphere and is integral in sparking severe storms.

The jet is also a highway of sorts along which storm systems propagate. That’s what you might hear television meteorologists refer to it as the “storm track."

For the next couple of weeks, the storm track looks to set up around 40 degrees north — or about as far north as Interstate 70 gets. There’s an outside chance that even the Mid-Atlantic could be subject to a few rounds of thunderstorms in the coming weeks if the region is able to break into the “warm sector” of low-pressure systems scooting just to the north.

“The increased risk for severe weather is anticipated to be displaced slightly north of its typical location during March,” according to the Climate Prediction Center.

Storm readiness


Debris from storm-shattered homes is scattered near Cookeville, Tenn., on March 3. (Mark Humphrey/AP)

Of course, weather is fluid, prone to change. This far in advance, there is no way to know what exact outcomes or impacts will be, but the broad pattern hints at repeated rounds of strong to severe thunderstorms in the coming weeks. Details beyond that will be fine-tuned as we approach individual events.

But this forecast is a helpful reminder to begin developing a severe-weather plan, if you haven’t already. Where will you go to seek shelter if a warning is issued for your location? How long will it take you to get to your place of refuge? Are there other vulnerable individuals, including children and the elderly, reliant on you? And how will you be notified of impending severe weather?

Discussing your severe-weather plan with your family is integral, as is procuring a weather radio with battery backup that can alert you in the dead of night — even if cellphone service is compromised. (The recent spate of tornadoes in Tennessee underscores the need for a way to be adequately notified.)

We’ll continue monitoring the situation in the coming days and weeks.