Traveling to visit family and friends could turn into a major hassle across much of the East Coast as Winter Storm Cato is poised to develop, spreading rain and snow across a highly populated and heavily-traveled region of the country on the day before Thanksgiving.

(MORE: Thanksgiving Travel Forecast Nationwide)

A cold front currently sweeping toward the East Coast is expected to stall just offshore late Tuesday. Low pressure will spin up along the tail end of the front over the Gulf of Mexico on Tuesday.

Winter Storm Watches, Warnings and Advisories

That low will quickly cross Florida Tuesday evening and then intensify as it moves north-northeastward Tuesday night into Wednesday, most likely staying just off the Eastern Seaboard. This is a classic track for a significant East Coast storm.

However, as is often the case, key questions remain about the exact outcome from this storm system -- and the small details could make a big difference for your travel plans, especially if you will be driving in the Mid-Atlantic and the Northeast on Wednesday or Wednesday night.

The National Weather Service has issued winter storm watches for more than 20 million people in the Mid-Atlantic and Northeast. In this case, the watches mean significant snow accumulations are possible within the next 48 hours.

Here's an overview of how the storm is most likely to play out.

Current Radar

Tuesday night: The first snowflakes from this storm will begin flying over the Smoky Mountains near the North Carolina-Tennessee border Tuesday night. Snow will spread to the mountains of eastern West Virginia later at night. Amounts in these areas should be relatively light.

Aside from that, most of the precipitation will still be in the form of rain Tuesday night, reaching as far north as the New York City area by the start of the Wednesday morning rush hour.

Wednesday Forecast

Wednesday: Snowfall will expand its areal footprint dramatically Wednesday over the Northeast. The rain/snow line will likely hover somewhere close to the Interstate 95 corridor.

The forecast is complicated by the fact that the cold side of this storm system isn't particularly cold. While it certainly looks cold enough for snow over a swath of the interior -- say, from West Virginia through central Pennsylvania, the Catskills of New York and into interior New England -- areas closer to Interstate 95 may have ground-level air temperatures a few degrees above freezing.

In this case, we'll be watching for heavy snowfall rates caused by fast-rising air associated with the low-pressure system. If it snows hard enough, air temperatures may cool enough for the snow to reach the ground and accumulate quickly.

Conversely, in areas where precipitation isn't as heavy, the air may stay just warm enough to melt the snowflakes before they reach the ground -- resulting in a cold rain or a rain/snow mix. Most if not all of the Washington-to-Boston urban corridor is in this zone where uncertainty is greatest. Snowfall amounts could vary wildly over short distances in this zone.

In any case, while the snow/rain line makes a big difference for drivers, major airports are likely to be in bad shape regardless. Either rain or snow, combined with the low clouds and blustery winds sure to accompany the storm, will likely cause severe delays at already-crowded airports up and down the Mid-Atlantic and Northeast coast.

Wednesday Night Forecast

Wednesday night: The fast-moving storm will keep booking to the northeast, wrapping cold air southward on its back side. This should allow the rain/snow line to advance southeastward across the Northeast Megalopolis, but by this point precipitation will be diminishing in intensity.

Snowfall should quickly come to an end from the New York City area southward before midnight.

Farther north, snow will continue over much of New England into the evening, ending from west to east later Wednesday night.

Thanksgiving Day: The last of the snow will wind down in the morning over parts of Maine. In the wake of the storm, highs will be below average across the Northeast. But they should climb far enough above freezing to allow rapid improvement in road conditions.

48-Hour Snowfall Forecast

Snowfall amounts and impacts: The inset map at right shows our latest 48-hour snowfall forecast. Confidence in exact amounts is lowest along the Interstate 95 corridor, and somewhat higher to the north of west.

Total snowfall isn't the only thing to consider, however. Temperatures will be close to the 32-degree mark for most of the affected area, so this will be a heavy, wet snow. This could lead to broken tree limbs and power outages in areas where the snow is heaviest.

But it could also mean less impact on drivers where amounts are lighter, where roads may just be slushy or wet. Bear in mind that temperatures were in the 70s on Monday in parts of the Northeast, so ground temperatures are not very cold.

The rate of snowfall is also important. Some areas, especially closest to the rain/snow line, could see snowfall rates of 1 inch per hour or more. Road conditions can deteriorate very quickly in snows of that intensity, as the snow can fall faster than road crews can clear it with plows. Even where the soil is warm, heavy rates of snowfall can allow snow to accumulate much faster than the ground can melt it.

The storm naming committee at The Weather Channel continues to evaluate the forecast. If the storm appears likely to meet our criteria, it will be named Winter Storm Cato.

Stay with The Weather Channel and weather.com for updates on this high-impact storm system.

MORE ON WEATHER.COM: Winter Storm Cleon, December 2013 (last year's "C" storm)

Joseph Mezo uses an umbrella as he walks to work in light sleet and icey conditions Friday morning, Dec. 6, 2013, in Dallas. (AP Photo/LM Otero)