The Washington PostDemocracy Dies in Darkness

Major storm bringing snow to Plains and Midwest, with tornado risk in South

More than a foot of snow is likely in parts of the Corn Belt, with travel disruptions probable

The American GFS model simulates the development of the Great Plains weather system that will also affect the Deep South. (Pivotal Weather)

A dynamic storm system is rolling across the Lower 48, packing a punch as it delivers heavy snow to some areas and severe thunderstorms to others. More than 15 million Americans — from Colorado to Michigan — are under winter weather alerts. Across the South, meanwhile, a tornado watch is in effect from eastern Texas into Arkansas through Wednesday afternoon.

The potential for tornadoes comes amid a record-busy stretch that’s made January resemble April. At least 124 preliminary reports of tornadoes have been received by the National Weather Service so far this month, far outweighing the January average of three-dozen tornadoes.

It’s January, but tornadoes keep spinning up like it’s April

As the storm progresses eastward, the tornado potential will spread into northern Ohio on Thursday, including Columbus, Dayton and Toledo. Normally, Ohio is bracing for snow at this time of year; Toledo’s average mid-January high is around 34 degrees.

On the storm’s cold side, north and west of its center near the Oklahoma-Kansas border, ice and snow have proved disruptive in the Central Rockies and Central Plains. A half-inch of ice glazed over Goodland, Kan., on Tuesday night, while downtown Denver got 3 or 4 inches of snow. At Denver International Airport, to the east, 7.7 inches fell through midmorning Wednesday. It proved to be Denver’s largest January snowstorm since Jan. 7-8, 1992, based on airport measurements. The Stoner region of southwest Colorado picked up more than a-foot-and-a-half.

The same overarching system will drag a cold front east, spreading rain toward the East Coast on Thursday into Friday, with snow and ice in interior New England.

The setup

On Wednesday morning, a zone of low pressure was located near the Oklahoma-Kansas border. It was being energized by an approaching pocket of cold air and spin aloft, and will subsequently intensify in the hours ahead. A second wave of low pressure will form along the cold front over the Missouri Ozarks, riding northeast in tandem through Friday before strengthening and becoming the dominant storm center off the coast of New England.

Low pressure zones spin counterclockwise in the Northern Hemisphere, so a warm, humid air mass will be drawn northward across the southern states. On the back side of the low to the northwest, frigid air will be dragged southward from Canada.

That means moisture wrapping around the low from the south will be forced up and over the cold air, falling as heavy, wet snow to the west and north of the low pressure center. To the east and south in the “warm sector,” strong to severe thunderstorms are anticipated instead.

Severe weather

The National Weather Service Storm Prediction Center has hoisted a Level 2 out of 5 risk for severe weather over the lower Mississippi Valley. It includes Jackson, Tenn., Memphis, Little Rock, Shreveport and Alexandria, La., as well as Bossier City, La. A Level 1 out of 5 risk surrounds the Level 2 that encompasses Houston, Nashville, Jackson, Miss., and Baton Rouge.

Thunderstorms will form along the leading edge of a cold front that will push east during the afternoon and evening hours. The active weather was already underway in East Texas during the midmorning hours, where a tornado watch was issued, extending to the northeast into central Arkansas, including Shreveport, La. and Little Rock.

As the front moves into more unstable, or juicier, air to the east, thunderstorms will increase in coverage and intensity. They’ll eventually merge into a line with damaging straight-lines winds and embedded kinks of rotation, a few of which could produce some quick-hitting tornado spin-ups.

There’s a chance that a few initial storms will remain discrete, or isolated from neighbors, and result in a slightly greater tornado chance. That will accompany storms growing vertically into a sheared environment, or an atmosphere characterized by changing winds with height. That will allow thunderstorms to rotate.

The storms will reach south-central Arkansas shortly after noon, then enter northwestern Louisiana and continue slowly trekking east. They should make it to the Mississippi River by near or just after nightfall. Storms may fade a bit overnight, but some models indicate a restrengthening into early Thursday morning as they enter southeast Mississippi and western Alabama.

Winter weather

Winter storm warnings blanket much of northeastern Colorado, virtually all of Nebraska, northwestern Iowa, southern Minnesota and a swath of Wisconsin. A winter storm watch extends into northeast Wisconsin and northern Michigan. That’s where the heaviest snows are expected to fall, with totals of 9 to 13 inches likely in the heart of the band.

Snow was already coming down in Nebraska to start the day, prompting the National Weather Service office in Omaha to warn “Heavy snow could make tonight’s commute one of the worst commutes we have seen for several years.” It will pivot northeast with time, spreading over Iowa after dark. There may be some mixing or freezing rain in Iowa south of Interstate 80 for a few hours as liquid rain falls into a shallow subfreezing air mass.

The snow may linger across northeast Kansas, most of Iowa, southern Minnesota and much of Wisconsin through Thursday, though in a less intense state. Minneapolis, which lies on the northern edge of where significant snow is expected, is under a winter weather advisory for 3 to 5 inches.

While parts of Ohio could see thunderstorms on Thursday — some severe — cold air in the wake of the cold front could bring snow showers Thursday night into early Friday.

Into interior northern New England, several inches of snow could fall Thursday night into Friday. Closer to the coast, mostly rain is expected.

Loading...