After overloading on turkey, Black Friday deals and family, Americans headed back to school and work on Monday — but the weather is making the return to normalcy difficult for many in parts of the U.S.

A winter storm that left Americans battling poor weather conditions over the Thanksgiving weekend has returned to cause further disruption in the East. Some workers and school children are seeing their holiday extended after a mixture of rain, snow, sleet and wind is slowing their weekday morning commute, closing some schools and offices, and disrupting air travel.

Conditions are expected to improve by the end of the week, according to the National Weather Service (NWS). The storm is now beginning to abate and is expected to exit the Northeastern region by Wednesday. The storm was predicted to lead to 10 to 20 inches of snowfall by Tuesday morning from northeast Pennsylvania to southern Maine, where winter storm warnings remain in effect. Snow is also expected across the central Appalachians, and warnings are also in effect from western North Carolina to eastern West Virginia.

The storm is expected to continue causing major travel disruptions across the East, while conditions are improving further west across the Great Lakes and Ohio Valley as the storm moves away.

Here’s what you need to know about the most disruptive storms coming through this week.

Freezing rain and snow in the Northeast

The storm that wreaked havoc across the western and central parts of the country over the past week reached the Northeast on Monday morning. As predicted, heavy snow pummeled the northern Mid-Atlantic and New England and caused major travel disruptions, per the NWS.

On Monday, New York Gov. Andrew Cuomo declared a state of emergency in seven counties and deployed 300 members of the National Guard. Albany saw more than a foot of snow by Monday, according to the Governor’s office.

The storm is expected to leave up to 20 inches of snowfall from Northeast Pennsylvania and southern Maine by Tuesday morning. An additional 6 to 10 inches of snow are expected to fall on Maine before the storm ends by Tuesday night. Heavy snow will also fall across the Appalachian Mountains on Tuesday, and winter storm warnings are in effect from western North Carolina to eastern West Virginia.

Snow accumulated on Monday across major cities from Philadelphia to New York. While only about three inches of snow fell on New York City, Boston is expected to see up to 8 inches of snow by Tuesday night, according to forecasters.

On Monday, NWS reported that 16.4 inches of snow fell in Rowe, Massachusetts overnight, with more snow expected on Monday evening.

“We’ve got our shovels ready. We’ve got the snowblower ready. We’re prepared,” Paul Newman of Wethersfield, Conn., told the Associated Press.

Schools across the region, including in New Jersey and New England, closed preemptively because of the forecast of snow.

In New Jersey and Pennsylvania, tractor-trailers were banned or lower speed limits imposed on some highways, per AP.

“The winter storm is starting to redevelop along the Delmarva coast this evening,” the NWS Eastern Region tweeted in the early hours of Monday morning. “As this becomes the primary source center, it will move slowly northeast up the coast Monday into Tuesday, producing additional heavy snowfall for parts of the Eastern U.S.”

Rain and snow adds to misery out West

The NWS predicts that a “plume of moisture” caused by a slow-moving storm over the eastern Pacific will continue to affect California. A burst of heavy rain and gusty winds reached Monterey Country on Monday morning, according to NWS Bay Area. Rainfall is expected to continue throughout California until midweek, and moderate to heavy snowfall is predicted for central Sierra Nevada. Snow showers are also likely in higher terrain in Nevada, Utah and western Colorado, according to NWS Weather Prediction Center.

Flooding is possible near the central California coast, where additional rainfall may exceed 1 inch, especially in areas affected by wildfire.

NWS Sacramento issued a winter storm warning on Monday and predicted “near white out conditions at times.” Across the Sierra Nevada, snowfall got as high as 46 inches in Kirkwood by Monday afternoon, according to NWS Sacramento.

Conditions improve in the Midwest and South

The conditions across the Ohio Valley and the Great Lakes will improve this week as the storm moves away from the region toward the East, per the NWS.

In Sioux Falls in South Dakota, the local NWS predicts a drier week, with the mildest days being on Tuesday through Thursday. The roads remain slippery on Monday from “the hectic weekend weather.”

Further South in Memphis, Tenn., weather conditions will also improve this week, with most of the Midsouth experiencing highs in the 40s.

Flight delays affect travel

The winter storm led to numerous flight delays and cancellations, with at least 900 flights into or out of the U.S. cancelled on Monday, and at least 19,800 delays, according to Flight Aware. Many of the cancelled and delayed flights were from airports in the New York, Boston and San Francisco areas.

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