A multiday stretch of severe weather begins Monday and will carry though at least Thursday as repeated rounds of severe thunderstorms target the Plains, Midwest and Mid-South. Strong tornadoes are possible both Monday and Tuesday over the central states, including after dark amid a chaotic — and concerning — weather setup.
Monday’s risk is a “conditional” one — meaning the ingredients for strong tornadoes are present, but it’s unclear whether they’ll overlap in the correct way to be fully tapped into. The same is true on Tuesday, when the bull’s eye of risk will shift from Kansas and Nebraska to Iowa and Missouri, though severe storms are possible all the way south to the Ozarks.
“Several tornadoes, large to very large hail, and damaging wind gusts all appear possible,” wrote the National Weather Service Storm Prediction Center. “Strong tornadoes may occur this evening across parts of Kansas and Nebraska.”
Both days have already been advertised by the agency to have a level 3 out of 5 “enhanced” risk for severe weather. Monday’s zone includes Lincoln, Valentine and Grand Island, Neb., as well as Hutchinson, Salina and Hays, Kan.; a level 2 out of 5 risk reaches down to Oklahoma City, and even stretches southwestward toward Abilene, Tex.
On Tuesday, Des Moines, Cedar Rapids and Iowa City are in the enhanced area, as is Columbia, Mo. The level 2 out of 5 risk encompasses Omaha, Kansas City, Chicago, St. Louis and Little Rock.
At least some risk of severe weather is anticipated to continue into Thursday.
The setup
On Monday, a high altitude disturbance — essentially a bowling ball of cold air, low pressure and spin aloft — was passing overhead near Las Vegas to the Four Corners to eventually the Colorado Rockies. That upper-air disturbance will help energize a surface low pressure system that will track from the Front Range to the Sand Hills of western Nebraska.
It’s that surface low that will draw north a ribbon of warm, humid air from the Gulf of Mexico, and drape it from Texas to southern South Dakota. That air mass will contain instability, which is storm fuel.
Behind that tongue of humidity, a bone-dry air mass will encroach out of the Desert Southwest. The boundary along which the two air masses meet is called a “dryline,” and that will be the impetus for severe thunderstorms.
Monday’s risk
Monday’s risk is tricky. While severe thunderstorms are possible in a broad area from the southern Plains to the central High Plains, there are limiting factors in some places that make it tricky to know if storms will fire at all. Holistically, there are three zones to watch:
- Western Oklahoma and northwest Texas: This is where models highlight the potential for a rogue rotating supercell thunderstorm to form Monday evening. If that is the case, damaging winds and hail would be the main concerns, though an isolated tornado couldn’t be ruled out. That said, “capping,” or a layer of warm air a mile above the ground, will act as a lid to suppress storm growth into the evening. It’s more likely that thunderstorms will erupt in a windy line along a Pacific cold front overnight, but it’s unclear how widespread they’ll be.
- Kansas: In Kansas, parameters are ripe for very severe thunderstorms with strong tornadoes — but storms might not even form at all. That’s again due to strong capping. (Imagine boiling a pot of water on the stove; the steam can’t rise if the lid is on the container.) There may, however, be a window between 6 and 9 p.m. for a few storms to form in the Garden City to Greensburg to Hays corridor, and rotating supercells with destructive hail and tornado potential would be possible. Then overnight, it’s probable that more storms form and create a line or clusters. (There may also be better convergence, or gathering of air, along the dryline in Kansas, bolstering the risk for storms, and a bit more easterly component to the surface winds, which would boost low-level spin.)
- Nebraska: In Nebraska, there will be more storms due to more “oomph,” or forcing — after all, the center of the low pressure system is nearby. Wind dynamics will support rotating supercell thunderstorms. But there could be too many storms, which would mean interference. It’s unclear how the risk will evolve into the overnight. At least some potential for strong tornadoes may be realized in south central Nebraska.
The risk into Tuesday
On Tuesday, the low-pressure system pushes to the east. The greatest severe weather risk will be in northern Missouri and Iowa.
The forecast environment will be challenging though. While wind shear, or a change of wind speed and/or direction with height, will be present, supporting rotation, it’s not known whether robust storm fuel will be available.
It’s likely that leftover storms from Nebraska and Kansas will push into Tuesday’s risk area, traversing the region during the morning as thunderstorms with heavy downpour and small hail potential. That line of storms may intensify into the afternoon with eastward extent.
If there is clearing, and sunshine can heat the ground in the wake of the first round of storms, then additional severe thunderstorm development, with the risk of tornadoes, would be possible.
More severe storms look possible over Kentucky on Wednesday and parts of eastern Oklahoma, northeast Texas and southwest Arkansas into Thursday.
