Days of tornadoes, damaging winds, large hail expected in central states

A steamy summertime pattern is brewing repeated rounds of severe weather, with tornadoes, destructive winds and large hail for some. Daily bouts of storms have been blasting across the Plains, and there are increasing odds that significant storms might make a run at the Mid-Atlantic and East Coast later this week.

Monday’s strongest storms impacted parts of Minnesota, including around the Twin Cities, and presented a tornado risk. On Tuesday, the bull’s eye is near Wichita and Kansas City, Missouri. Chicago is in the zone on Wednesday, and Thursday could bring storms to the Interstate 95 corridor – including Philadelphia, Baltimore and D.C.

June is a transition time in the atmosphere. The southern Plains begin shifting away from tornadic supercells, and instead the central United States tends to see large-scale thunderstorm complexes form virtually every night. Each of these brings winds gusting 60 to 80 mph.

Monday’s storms

A broad risk zone spans from Montana and eastern Wyoming to the Upper Midwest and central Plains, with two focused corridors to watch – one in Nebraska and the other in Minnesota. Both have been highlighted with Level 3 out of 5 enhanced risks drawn by the Storm Prediction Center.

Storms will blossom in a warm, humid air mass as an instigating cold front sags south. A few rotating supercells are possible initially, with eventual “upscale” growth into clusters. Supercells will pose more of a tornado threat, shifting to a primarily straight-line wind threat.

In Minnesota, there could be an extra tornado risk because of an MCV, or a mesoscale convective vortex, a weak swirl of wind left behind by Sunday’s storms over the Dakotas. As that swirl moves east, it helps strengthen easterly and southeasterly winds over Minnesota, bolstering low-level helicity, or spin. That increases the likelihood of a few spinning storms.

For Nebraska, it’s likely that scattered storms will coalesce into a squall line around sunset. This is most likely over north-central Nebraska. It will then move southeast with winds gusting over 70 mph at times. Hail up to half-dollar size is possible, too.

Elsewhere, a few severe storms are possible over the High Plains of eastern Montana, Wyoming and South Dakota as a low over the Rockies pinwheels gulf moisture northwest. Damaging winds and hail are the primary concerns.

Tuesday

Low pressure over western Kansas will be present to start the day, anchored on a cold front sagging south. A couple of rotating supercells could form along the front during the midafternoon in north-central Kansas along Interstate 70 – perhaps affecting places like Salina, Junction City or Manhattan. Tornadoes – perhaps even an isolated significant tornado – will be possible, as well as winds gusting over 60 mph and hail up to baseball size.

During the evening hours, those cells will merge into a potent squall line that may be accompanied by a secondary squall working in from the northwest. Both squalls could produce damaging gusts and a few embedded destructive gusts over 75 mph.

Wednesday

Scattered severe thunderstorms will form along a cold front. A Level 2 out of 5 risk extends from Chicago to St. Louis to Joplin, Missouri, to Oklahoma City.

Initial rotating supercells will produce large, damaging hail up to the size of hen eggs. By midevening, it’s likely that storms will merge into squall lines with sporadic strong gusts and a very isolated tornado threat.

Thursday

The cold front should reach the Eastern Seaboard, with a couple of severe storms likely between New York City and Charlotte, North Carolina; the risk area also includes Baltimore, Philadelphia, D.C., Richmond and Blacksburg, Virginia. Damaging gusts and quarter-size hail are possible.