A powerful storm system is unleashing a severe thunderstorm outbreak across the southern Plains and portions of the Mississippi Valley from Friday into Saturday, with widespread damaging winds, along with the potential for tornadoes, a few of which could be strong, and heavy rainfall that could cause flooding. This storm will also bring other threats with it, from a full-on ice storm to heavy snow.
The Storm Prediction Center (SPC) has issued a "moderate risk" outlook of severe weather for the areas most likely to see damaging straight-line winds as the thunderstorms barrel through Friday afternoon into the overnight hours.
As storms approach southern Arkansas and northern Louisiana tonight, "a couple long-track tornadoes are possible," according to the Storm Prediction Center. With vicious storms continuing well after nightfall, the stage is set for a notably dangerous event.
Tornadoes that occur at night are especially dangerous due to the challenge of warning people who may be asleep.
Hail nearing the size of golf balls has already accompanied strong storms Friday morning in Oklahoma. A severe thunderstorm watch was issued early in the day, and by early afternoon, the first tornado watch of the day had been issued for parts of Oklahoma as well.
The potential exists for a long-lived squall line with a knack for producing significant damaging winds over multiple states. This may even qualify as a derecho event, depending how widespread the wind damage is.
In addition, along the squall line itself, quick-hitting tornadoes may form sporadically, with perhaps a few supercell thunderstorms popping ahead of the main line and lending themselves to an increased tornado risk. One or two of these tornadoes could be on the strong side.
Wind gusts greater than 70 mph will likely be common with this event. Power outages are possible, especially near the western border of southern Arkansas and northwest Louisiana. If you live in this area and your house does not have a place in which to shelter during storms, consider spending the night with friends or relatives whose does. Charge portable electronic devices and mobile phones prior to the onset of hazardous weather.
Storms will continue Saturday across Mississippi and Alabama.
Meanwhile, heavy rainfall caused by this system will lead to potential flooding farther north, up the Mississippi Valley and into the Corn Belt region, impacting Illinois, Indiana, and parts of the Ohio Valley as well.
On the storm's backside, encroaching cold air will flip rain to snow. In fact, some locales will deal with both strong thunderstorms and snow in the same day. Alva, Oklahoma found itself under a severe thunderstorm warning and a winter storm watch at the same time Friday morning.
As this dangerous storm systsem blasts east Friday night, wind gusts greater than 70 mph will likely be common. Power outages are possible, especially near the western border of southern Arkansas and northwest Louisiana. If you live in this area and your house does not have a place in which to shelter during storms, consider spending the night with friends or relatives whose does. Charge portable electronic devices and mobile phones prior to the onset of hazardous weather.
Ahead of this line, a few supercells could develop, but that hinges on whether or not cloud cover from the main complex limits daytime heating and destabilization Friday.
Overnight Friday, the low level jet stream will strengthen as it races north out of the Gulf of Mexico. Winds exceeding hurricane force will be present barely a mile above the ground. This will further fuel storm strength as the line redevelops Saturday morning and eyes portions of Dixie Alley.
Alabama and Mississippi are most at risk for Saturday's storms, which may feature a continued tornado risk.
One uncertainty concerns exactly how far north the low pressure system's "warm sector" gets. That's the zone ahead of the system's center where strong southerly winds gather heat and moisture, and it marks where the most unstable air mass will be located.
By Sunday, the severe risk is modeled to wane significantly east of the Appalachians. However, a subtle, marginal risk of severe storms may materialize in the lee of the mountains and in a few spots across the Southeast.
In addition to the severe storms, flooding will be problematic as well, as the powerful low level jet stream will transport copious amounts of moisture northward.
Flash flood watches stretch from Oklahoma and north central Texas up the Mississippi Valley and near the Great Lakes, including Chicago and approaching Cleveland. A widespread 2 to 4 inches of rain is possible late Friday through Saturday, with localized 5 inch amounts.
Heavy rain is possible in the Northeast on Sunday.
On the system's backside, precipitation will fall in the form of heavy snow. Along the boundary between chilly air to the north and unseasonably mild air down south, an ice storm is possible.
In northern Oklahoma, a coating to an inch of snow is likely beginning Friday night and wrapping up Saturday. A general 1 to 2 inches appears likely in much of northwest Missouri and eastern Kansas. Kansas City will find itself beneath a blanket of white.
A plowable snowfall, perhaps approaching half a foot, is possible in northeastern Iowa, extreme northwest Illinois, and much of southern/central Wisconsin. Additional heavy snow will target northern Michigan.
Meanwhile, a narrow zone of ice accretion is possible somewhere along the Mississippi River region that divides Iowa from Illinois. That strip will extend northeastward; about a quarter inch of glaze, give or take, is possible, which will cause slick travel and possibly some power outages.
More formidable icing can be anticipated in central Michigan, including Lansing and Flint. A full-fledged ice storm is possible there. In fact, temperatures aloft may approach 50 degrees while surface temperatures will hover in the 20s. It's the classic setup for rain falling and freezing, clinging to trees and powerlines, potentially bringing both down.