Storms knocked power for thousands around Great Lakes region, with more tornado risk coming

After widespread thunderstorms and some tornadoes knocked power out to hundreds of thousands of customers in the Great Lakes region, a continued severe weather outbreak is expected through Friday night. It will be the third-straight day of significant severe weather, with more threats through the weekend.

Storms are expected in the Ohio, Tennessee and Mid-Mississippi valleys, where there are threats of strong tornadoes, widespread damaging winds and large hail. Some flooding is also possible. The National Weather Service has issued a moderate (Level 4 out of 5) severe thunderstorm risk in the region.

More than 400,000 customers were without power early Friday following severe thunderstorms across the Great Lakes region late Thursday, according to PowerOutage.us. Michigan woke up to 250,000 outages, with the highest concentration of power loss in a zone around southern Lake Michigan.

Amid numerous high-wind reports, more than a dozen reports of twisters have been logged from the Upper Midwest to the Great Lakes.

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n Wisconsin, a visibly striking tornado spun through fields in New Richmond, northeast of Minneapolis, while another caused significant damage in nearby Hammond.

Up to baseball-size hail also fell from the most powerful storms. In Wisconsin, Madison had a hailstorm in the early evening, dropping hail up to 2 inches in diameter. In Chicago, Beyoncé’s first night of her Cowboy Carter tour was delayed for two hours as severe thunderstorms passed through the area.

The thunderstorms are shifting southeast Friday.

Cities that may see serious tornadoes and wind include St. Louis; Paducah, Kentucky; Louisville; Evansville, Indiana; Indianapolis; and Nashville.

An overlapping flood concern could also develop. Portions of the same region are under a slight (Level 2 of 4 risk) for flooding, including much of Kentucky and parts of Tennessee.

Intense storms may also roam from East Texas to the mid-Atlantic. The severe weather risk stretches more than 1,200 miles in total.

And once this storm system winds down, another will be winding up to the west. Strong tornadoes are in the forecast by Sunday for parts of the Plains.

Friday storms

A severe weather outbreak is likely Friday in the mid-Mississippi, Ohio and Tennessee valleys. The Storm Prediction Center is warning that “several strong tornadoes are expected, and a long-track high-end tornado will be possible.”

There could also be some hurricane-force winds as storms merge into a squall line.

Scattered rotating supercells will form in southeast Missouri and southern Illinois in the afternoon. Any lone, discrete supercell will have the potential to produce a significant tornado of EF2 strength or greater (out of 5 on the Enhanced Fujita Scale), hail to baseball-size and damaging winds. This includes around the St. Louis metro area, but the greater risk will be closer to Carbondale, Illinois, and Cape Girardeau, Missouri.

A weak surface low is taking shape over Illinois. The greatest chance for an intense supercell is somewhere over southeast Missouri/the Bootheel, southern Illinois, southwest Indiana and southwest Kentucky. That’s where all the fronts meet near a surface low-pressure system, and there’s extra spin near the center of surface low pressure.

There could also be a sneaky supercell near or south of the warm front in Kentucky during the afternoon.

One potential limiting factor is that surface winds are out of the southwest. To get a greater tornado threat, the atmosphere often requires surface winds more out of the southeast to contrast with southwesterlies at the mid-levels. The changing wind direction with height would more efficiently spin storms.

Weekend storms

Saturday storms are likely across the southern Plains and Texarkana region. Dallas-Fort Worth, Texarkana and Little Rock are in a slight (Level 2 out of 5) risk of severe weather.

The main hazard will be storms producing large, damaging hail — perhaps up to egg-size or larger. Hailstorms could quickly become disastrous and costly if they occur in the vicinity of the Dallas metro.

An isolated tornado is also possible.

A weak surface low is expected to form over southwest Kansas. That will help strengthen a dryline — the clash between bone-dry desert air west and moisture-rich Gulf air east. The dryline will become established over western Oklahoma and Central Texas.

Ahead of the dryline will be a very warm and humid air mass. That juiced-up atmosphere will contain moderate to extreme thunderstorm fuel. Once storms fire up, they’ll blossom quickly. Air will rise very fast, resulting in rapid updrafts capable of suspending hail long enough that it grows large and damaging.

Next week

Moving into early next week, there will be additional rounds of severe thunderstorms Sunday, Monday and Tuesday along the Interstate 35 corridor in north Texas, Oklahoma and Kansas. Several storms each day will be rotating supercells with an attendant risk of large to giant hail, tornadoes — perhaps strong — as well as destructive winds.

A jet stream dip over the Rockies will allow periodic insurgences of cool air to slide east across the High Plains. That cool, dry air will kick up moisture to the east, forming storms. And with the jet stream screaming overhead, storms will tap into winds aloft and spin, yielding a tornado risk.