By Christina Maxouris, CNN

(CNN) -- Severe weather is expected to stretch from coast to coast Tuesday, with about 86 million people under some sort of winter alert, millions facing a flood threat and more snow on the way in Seattle.

Throughout the Northeast, snow in the late morning or early afternoon is expected to give way to sleet and possibly freezing rain before a steady rain sets in.

The metropolitan areas of Philadelphia, New York and Boston could see 4 inches of snow followed by a coating of ice. Interior sections of the Northeast could see a foot or more of snow, while the storm is mainly expected to drop freezing rain in southern Pennsylvania and Maryland.

More than 730 flights into and out of John F. Kennedy and LaGuardia international airports in New York had been canceled as of mid-morning, according to FlightAware. More than 2,100 flights were canceled Tuesda across the country.

Winter storm warnings or winter weather advisories have been issued across Massachusetts through the night. The evening commute could be a tough one for Bostonians, as the few inches of afternoon snow succumb to heavy sleet and eventually rain.

In New Jersey, officials declared a state of emergency in anticipation of the weather. Officials closed state offices, banned commercial vehicles on some highways, and restricted speeds to 45 mph on parts of the Garden State Parkway and the New Jersey Turnpike.

"The afternoon commute will likely be a slow slog, as roads will remain slick with any residual ice and freezing rain," New Jersey Gov. Phil Murphy said. "Ice is probably our overriding, collective concern."

Several cities including Chicago, Detroit and Buffalo, New York, could also see dangerous travel conditions as a band of sleet and ice could make roadways treacherous.

A band of heavy snow also will set in over northern Iowa, Wisconsin and Michigan, where residents could shovel away up to 12 inches Tuesday morning.

Winter warnings, watches or advisories stretch from the Upper Midwest through western Virginia and up to Maine.

Ohio Valley flood threat

Widespread rain will continue to soak the Ohio Valley, from Arkansas to Ohio. As much as 4 inches could fall.

More than 53 million people are under a flood warning, flood advisory, flash flood watch or flash flood warning across the country. Cities including Nashville, Little Rock, Louisville, Lexington and Cincinnati could see flooding.

More snow in Seattle

Meantime, Seattle, which broke its February snowfall record not even halfway into the month, hasn't seen the end of the white stuff.

A few inches of snow are possible around the area, with heavy snowfall expected just west of town. Winter alerts also are in effect in the region.

Farther south, the Sierra Nevada mountaintops in California can expect to continue to be pounded with snow over the next few days. Extreme winds are also forecast in the Sierra, with gusts of more than 100 mph.