A soon-to-develop winter storm is set to unleash a slew of unwelcome wintry slop across much of the central and Eastern United States, plastering some areas with up to a foot of snow and bringing sleet, rain and ice to others along the coastline.

Travel disruptions could affect a number of major East Coast cities near the end of Martin Luther King Jr. Day weekend before a rush of bone-chilling air arrives toward the middle of next week.

The storm hasn’t even developed yet, as its instigating ingredients are still thousands of miles away over the eastern Pacific, but weather models are unanimous in their depictions of a whopping wintry wallop. What is less certain, however, is the exact track of the system, which will have a bearing on precipitation types.

The storm will manifest in two phases — one that dumps nearly a foot of snow over the Corn Belt and Upper Midwest on Friday and Saturday, and a second act beginning Sunday as the parent low-pressure system sweeps up the East Coast. While precipitation type is more uncertain along the major hubs of the Eastern Seaboard, confidence is growing that interior areas near the Appalachians could be dealing with a higher-end event. There’s even a chance that flakes fly in places such as Birmingham, Ala., and Atlanta.

The system now

As of lunchtime Wednesday, the disturbance was located about 1,000 miles offshore of Oregon over the eastern north Pacific. The “shortwave trough,” or a lobe of cold air, low pressure and spin nestled within a dip in the jet stream, was set to arrive over the Pacific Northwest on Thursday.

That will spell an end to the atmospheric river and subsequent fire hose of moisture lashing Washington state, as well as deliver a blanket of snowfall in the higher elevations of the Cascades and across the Columbia River basin of Idaho and western Montana. From there, the storm will dive southeast, helping intensify a surface disturbance near the Texas Panhandle. A strip of low pressure will extend to its north, with cold northwesterly winds in the lee of the Rockies reinforced by high pressure over Manitoba and Ontario.

A ribbon of moisture will snake north from the Gulf of Mexico, curling around the surface low and depositing a strip of snowfall over parts of the northern Plains and west of the Great Lakes. From there, the Ozarks and areas near the Ohio River will be next in line for snow before the storm curves up the Ohio Valley or Appalachians on Sunday and Monday.

Upper Midwest and Corn Belt

Meteorologists will have a better idea of what will happen with the system come Thursday, when it moves ashore over Washington state and can be sampled by weather balloons. That will provide better data that can be pumped into weather models, narrowing down what might transpire.

Heavy snow will drop southeast through central and eastern North Dakota, the James River Valley of South Dakota and adjacent southwestern Minnesota. Cities such as Fargo, Grand Forks, Sioux Falls, S.D., and Des Moines could all see more than six inches of snow, with an outside shot at topping a foot.

Interstate 29 will be heavily impacted and potentially impassible for a time late Friday into Saturday, though winds should, fortunately, remain light.

Ozarks and Tennessee Valley

From there, uncertainty builds in where exactly the system, which will be sweeping southeast Saturday afternoon, makes its left turn. That will have enormous beatings on how much snow will fall across parts of Missouri, Arkansas and Tennessee.

As the low begins to change direction, it will also initiate an energy transfer to a fledgling low farther east. It’s also not clear exactly where that low will become established nor where ultimately it will track.

Southern Missouri and northern Arkansas have the best risk of a plowable snow exceeding four inches, and Memphis, too, could get into the action. The time frame to watch for them would be from Saturday evening to Sunday.

A few flakes may come down in northern Mississippi and the Appalachian foothills of Alabama and Georgia, though a cold rain is the most likely scenario. Still, it wouldn’t be impossible for a few flurries to occur even in the Atlanta metropolitan area.

East Coast impacts

Uncertainty abounds on the East Coast, where the track of the low still has to be ironed out.

An offshore track would swirl down more cold air on the back side of the storm, keeping most of the East Coast in snow throughout the duration of the event. Too far inland, and a warm conveyor belt will bring mainly rain near the coastline. The most likely scenario is for a coastal hugger or an “inside runner,” which would entail the low tracking directly up Interstate 95.

A reasonable first stab at snowfall totals would place the bull’s eye over parts of eastern Ohio, West Virginia, New York state, interior Pennsylvania, western Maryland and western Virginia, as well as in the mountains of eastern Tennessee and western North Carolina. A broad 6 to 10 inches, with a few folks well over a foot, is probable. Northern New England will probably be cold enough for all snow, too.

For cities such as Washington, Baltimore, Philadelphia, New York, Boston and Hartford, Conn., the forecast is considerably trickier — odds are precipitation will start as snow thanks to cold air entrenched near the surface, but eventually flip to sleet and ultimately rain as milder air moves ashore. It’s important to note that could change, however, depending on the track of the system. There’s still a chance for a “boom” scenario with more snowfall than currently anticipated.

Icing could be a concern in parts of the Carolinas, where cold, dense air east of the mountains will hug the surface. Warm, juiced-up and moisture-loaded air will “overrun” atop it, producing rain that will fall into the chilly layer and potentially freeze on contact with the ground. Once again, it’s too early to pinpoint where that may occur, but it’s something to be aware of.

The system will clear the Northeast on Monday evening, with very cold air building in its wake. Temperatures will be about 15 degrees below average to kick off Tuesday of next week.