May 16, 2019

An Extended Period of Severe Storms Is Likely in the Central U.S. Starting Friday



A multi-day severe weather event will begin to unfold across the central United States beginning on Friday and lasting through early next week. It's been a while since we've seen a favorable setup that leads to a back-to-back(-to-back-to-back-to-back) severe weather threat like we're about to see unfold. Each day carries the risk of tornadoes, large hail, damaging winds, and flash flooding from torrential rainfall.



Five days of severe thunderstorms will occur in two rounds. The first round will begin Friday from western Texas northward to the Upper Midwest, with the severe threat sliding eastward Saturday and again on Sunday. The second round of severe weather will shift back to the central Plains on Monday—likely including Dallas-Fort Worth, Oklahoma City, and Wichita areas—moving east of there on Tuesday.

Despite some of the chatter that's caused my friends and followers some consternation over the last couple of days, the extended nature of this severe weather threat won't necessarily translate to an intense outbreak. It's prime time for tornadoes on the Plains, and it's likely that at least some of the tornadoes that occur will be on the stronger side. Five days of severe weather doesn't mean we'll see a Twister-like sequence of mile-wide wedges gnawing away at wheat fields each day, but rather that conditions will be favorable for dangerous thunderstorms over a longer period that we've gotten used to seeing over the last couple of years.

Classic supercells are dangerous, of course, but even a sloppy field of thunderstorms can produce damaging wind gusts, large hail, and extremely heavy rain that leads to flash flooding. Just because everything isn't a major tornado outbreak doesn't mean the threat can be shrugged off.

Heavy Rain




Before getting into the severe threat, it's important to note that the central part of the U.S. is expecting a lot of rain over the next couple of days from these thunderstorms. The joy of convection is that not everyone will see all of the rain predicted, and some will see much more than what's shown on the map. This heavy rain will lead to flash flooding in some areas, and it will exacerbate ongoing river flooding.

First Round—Friday/Saturday/Sunday

A trough in the jet stream moving over California—which brought the state some heavy rain and mountain snow—will cross the Rockies on Thursday night and set the stage for the first round of severe weather. A low-pressure system will develop at the surface and cross Nebraska during the day on Friday, providing the focus for thunderstorms to develop. Southerly winds at the surface will drag warm, humid air north from the Gulf, providing plenty of fuel for thunderstorms to quickly intensify once they pop up.

Friday:



The Storm Prediction Center on Wednesday issued an enhanced risk for severe weather for parts of Texas, Kansas, and Nebraska on Friday. The enhanced risk is split between two areas because of the different mechanisms expected to drive the storms.

The southernmost risk, encompassing parts of western Texas and Oklahoma, will develop along a dry line. A dry line is a sharp boundary separating areas of high moisture and low moisture at the surface, making them really easy to spot on dew point maps. If you learned about supercells and tornadoes in school, dry lines in Texas and Oklahoma probably featured prominently in your lessons.

A dry line pushing into an unstable environment can serve as a focus for the development of supercells capable of producing tornadoes, very large hail, and damaging wind gusts. Forecasters believe that's possible in parts of Texas and Oklahoma on Friday.

The other area of enhanced risk is closer to the low-pressure system at the surface in Nebraska. The warm sector near the center of a surface low is often a favorable area for focused severe thunderstorm development. The SPC's outlook on Wednesday said "very large hail" and tornadoes are possible there on Friday.

Saturday and Sunday:

Severe thunderstorms will likely form early Sunday ahead of a cold front advancing into central parts of Kansas, Oklahoma, and Texas. Tornadoes are large hail are more likely in discrete storms that form in the warm sector, while damaging winds and quick tornadoes are favored in storms that develop into squall lines. The threat for severe weather will shift toward the Mississippi River Valley on Sunday.

Second Round—Monday/Tuesday

Another trough will drop over the southern Rockies this weekend and emerge over the south-central Plains on Monday, providing the focus for the second round of severe thunderstorms. The latest forecast from the SPC has Monday's risk centered on parts of Texas, Oklahoma, and Kansas, shifting a little farther to the east on Tuesday. All modes of severe weather will be possible with this second round of storms. Forecasters will have a better idea about locations and specifics once we get closer to the second round of storms.

The forecast for specific locations on the maps above will likely have changed by the time you read this post, so, as always, it's a good idea to visit the Storm Prediction Center a few times a day during the warm season to keep up with their latest forecasts.

[Model Image: TwisterData.com]

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I graduated from the University of South Alabama in 2014 with a degree in political science and a minor in meteorology. I ran Gawker's The Vane for two years and I've contributed to Mental Floss, Forbes, Popular Science, and the Washington Post's Capital Weather Gang. I also teamed up with Outdoor Life to write a book called The Extreme Weather Survival Manual, which came out in October 2015.

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