Severe weather risks dot central U.S. as calendar flips to April
The calendar is flipping to April, and with it comes an atmospheric shift more conducive to severe thunderstorms and heavy rains over much of the United States. That includes expected severe weather this week.
Multiple days of severe weather are expected through Saturday, with at least some potential for a few tornadoes Wednesday and Friday. As Gulf of Mexico waters, already milder than average, continue to warm, more moisture will waft north over the central states. It’s why the spring months tend to be the most prolific for tornado activity in the U.S. – particularly April and May.
The upcoming pattern may also lead to wetter-than-average conditions, with a few pockets of flooding in the lower and mid-Mississippi Valley and parts of the Ohio Valley.
The sudden switcheroo in the atmosphere comes after a historic heat dome shattered dozens of March high-temperature records across the West. One Florida-based meteorologist described it as “like nothing we’ve seen before in March,” with temperatures that would be impressive even by May standards.
That heat dome has finally “broken down,” allowing a more progressive weather regime to become established – one that features the west-to-east movement of weather systems and dips in the jet stream. These jet stream dips, known as “troughs,” will be responsible for inciting severe weather.
Cooler air and low pressure will become established over the Rockies, meanwhile, as the central and Eastern U.S. heat up. As periodic insurgences of cool air impinge on warmth and moisture to the east, storms are likely.
According to the National Oceanic and Atmospheric Administration’s Storm Prediction Center, the United States averages about 500 tornadoes between April and May. As summer’s warmth attempts to build, it clashes with the gradual retreat of winter. That brews strong storms – and, with the jet stream still roaring overhead, some of those storms can rotate.
Outlook for Monday
On Monday, a slight (Level 2 out of 5) risk of severe weather was drawn across northeast Iowa; southern Wisconsin, including Madison; Des Moines, Davenport and Cedar Rapids, Iowa; and Rockford, Illinois. A few hailstorms are expected Monday night, with the potential for a few instances of large hail up to hen egg-size.
Storms will be rooted in milder air above a shallow surface cool layer on the north side of a west-to-east stationary front. Warmth and moisture will ride atop that cool air, generating thunderstorms.
Because of cool surface temperatures, tornadoes aren’t expected.
Thunderstorm coverage will increase after midnight.
Outlook for Tuesday
On Tuesday, a slight (Level 2 out of 5) risk of severe weather exists from northeast Illinois and northwest Indiana, including Valparaiso and South Bend, eastward to Buffalo and Cleveland. Southern Michigan is included, as are Detroit, Lansing, Kalamazoo and Ann Arbor.
An upper-air disturbance will help generate showers and thunderstorms along a west-to-east frontal boundary. Hail, wind and an isolated tornado are possible, but uncertainty abounds.
Meteorologists are unsure how far north the instigating frontal boundary will lift, which casts doubt on the northern extent of the warm sector of warm, humid air.
Likewise, the storm mode is challenging to ascertain. Will a few rotating supercells form? Or will thunderstorms quickly merge along the draped frontal boundary, becoming messy and unable to rotate?
The forecast will become clearer in coming days.
Outlook for Wednesday onward
On Wednesday, a cold front will sag through Kansas and approach the Oklahoma border. It will intersect a dryline, or the leading edge of dry air encroaching on moisture to the east. Combined, a few rotating supercell thunderstorms may sprout in western North Texas or western Oklahoma, quickly merging into windy lines or clusters. Somewhat dry surface conditions means that wind and hail will be the primary concerns, at least initially. A brief, isolated spin-up tornado is possible as any squall lines encounter greater low-level moisture overnight while they approach the Interstate 35 corridor.
Thursday will be a transition day.
The leftovers from Wednesday’s storms will push east into the Mississippi Valley, and perhaps the Midwest, in a weakened state; only isolated severe weather will be possible. A new upper-air disturbance, meanwhile, will be taking shape over the West.
That’s why Friday will feature a renewed chance of severe thunderstorms over the central and southern Plains and perhaps parts of the Corn Belt. Another low-pressure system, likely stretching from Kansas into Iowa, will trigger the development of scattered rotating supercells. Hail, wind and perhaps a tornado threat are likely before lone cells merge into windy squall lines.
Tornado reports this year
There have been 274 tornado reports across the United States this year.
That compares to a long-term average of just over 200 tornadoes through late March. This time last year, there had been over 300 tornado reports.
Here’s a list of the states with the most tornado reports through Sunday .
- Illinois, 49.
- Mississippi, 39.
- Louisiana, 31.
- Oklahoma, 20.
- Alabama, 19.
These tornado counts are expected to grow in the weeks ahead, as the peak of severe weather season begins in some states.