A sprawling storm system gathers strength over the Central Plains on Monday. (CIRA/RAMMB/NOAA)
By Matthew Cappucci
Matthew Cappucci
Meteorologist, Capital Weather Gang

A strong storm system is sweeping across the country this week, bringing a variety of high-impact winter and springlike weather. Heavy snow, strong to severe thunderstorms and drenching rainfall that could exacerbate already serious flooding are possible for millions as the storm treks east through the midweek, ushering in a sharply colder air mass that will settle in by the weekend.

Behind the storm, significant lake-effect snows are possible downwind of the Great Lakes, which because of the relatively mild winter have large expanses of open water. This is unusual for such a late winter date.

[What happened to winter, and will it ever show up?]

The springlike storm system is more typical of late March, attesting to the unusually mild winter in the East. Strong to locally severe thunderstorms are possible Monday over the central Mississippi Valley, while farther to the north, a half foot of snow or more is in the cards for portions of the Corn Belt and the Great Lakes. Chicago is under a winter storm watch for what is likely to be the Windy City’s heaviest snow of the season.

Anomalous warmth and even some early-season thunderstorms could spread to the East Coast by Wednesday.

Thereafter, a foot of snow isn’t out of the question in some spots downwind of Lake Ontario by Friday. It’s an unusual time of year for lake-effect snow, which typically shuts down once the lake surface freezes over and starves the atmosphere of its main source of moisture, but Mother Nature doesn’t always play by the book.

Severe weather risk

The sprawling storm’s center of low pressure was anchored over the Central Plains early Monday, pivoting along the Oklahoma-Kansas state line as a moist and mild air mass crept northward on its eastern side. The Storm Prediction Center has issued a marginal risk of severe weather for eastern Arkansas, southeastern Missouri, northwestern Mississippi and western Tennessee on Monday.

A few supercells, or rotating, thunderstorms are possible, bringing the risk of isolated hail and locally damaging wind threats. A tornado isn’t out of question, although a tornado outbreak is not expected.

A limiting factor precluding a more organized severe weather threat is the extent of cloud cover spanning virtually the entire Southeast. This will suppress any surface heating that could increase instability and give rise to stronger thunderstorms.

Northern Plains and Great Lakes snow


The National Weather Service's forecast for heavy snow in the Great Lakes vicinity through Thursday. (WeatherBell)

Farther north, a system over the northern Plains and Rockies is bringing three to six inches of snow to the western Dakotas and the Nebraska Panhandle on Monday. Eventually, the upper-level energy driving that system will combine with the larger low to the east, resulting in a band of heavy snow late Monday night into early Wednesday.

That snow will form on the main system’s wraparound “comma head” as cold air filters in from the north. Snow will probably begin over eastern Iowa by early Tuesday and pivot north and east through Wednesday.

Computer models are projecting that Chicago could receive its heaviest snowfall in more than two years from this storm. A storm total of six to eight inches is possible, although the area of heaviest snow will be rather narrow. The National Weather Service is forecasting that up to 10 inches of snow could fall to the north and west of Chicago, but that bull’s eye could shift as the storm gets underway.

Regardless, the Tuesday evening and especially Wednesday morning commutes could be heavily affected, as will air travel through the hubs of Chicago O’Hare (American and United Airlines) and Midway Airport (Southwest Airlines).

Southeast rain … again


The European model's simulated rainfall through late Wednesday. (WeatherBell)

Meanwhile in the Southeast, copious moisture is in the forecast, too — which is unwelcome after weeks of showers and thunderstorms.

A widespread one to two inches of snow is possible over the next couple of days along the Interstate 20 corridor in Alabama and Georgia.

In Atlanta, the heaviest rain is likely overnight Monday into Tuesday.

[Severe flooding is underway along the Mississippi River, with more heavy rain in the forecast]

A second area of enhanced rainfall totals is likely over southern Georgia and northern Florida, with a sharp cutoff near Orlando caused by drier air in place south of there. Localized rainfall totals of up to three inches are possible in some spots in northern Florida, and can’t be ruled out in other parts of the Southeast, either. But this storm doesn’t look to dump more than an inch of rain on flooded parts of Mississippi.

Messy Wednesday in the East

By Wednesday, the system’s main areas of rain will move into the East Coast as a new low pressure center begins to form east of the Appalachians. Much of Wednesday will be fairly pleasant in the Mid-Atlantic, which will be nestled within the system’s dry slot. Temperatures could approach 60 degrees as far north as Washington, D.C.

As a cold front moves through later in the day, there’s a shot at some thunderstorms late Wednesday east of the Blue Ridge, from the nation’s capital east across the Delmarva and into southern New Jersey. There’s a threat for some severe weather, with a localized damaging wind risk not entirely out of the question. Cold-season severe weather setups are notoriously tough to predict. Often, as in events like this, low temperatures mean little instability is present to initiate storms, but stronger winds aloft encourage any storms that do form to bring strong winds down to the surface.

On Thursday, the coastal low pressure center looks to bring periods of heavy rain to interior New England and New York. Cold westerly winds behind the front will bring lake-effect snows east of Lake Ontario by Friday.