BIG SNOW: Forecast Changes for Maryland

UPDATE (9:41 p.m.)—The National Weather Service has upgraded its weather alert for Maryland to a winter storm warning, effective from 8 p.m. Wednesday to 8 p.m. Thursday.

A winter storm warning for heavy snow means severe winter weather conditions are expected or occurring and that travel will be dangerous, according to the weather service.

Snowfall will be six to 10 inches, with up to 12 inches at elevations above 800 feet, according to the weather service.

Snow will be "heavy," according to the weather service, which said the precipitation will move in from the south between 8 and 10 p.m. Wednesday, tapering off Thursday afternoon.

Winds will gust up to 30 mph Wednesday night and Thursday morning, according to the report. 

The weather service said people should only travel in an emergency. Anyone who must travel should take food, water and a flashlight, the weather service said.

Maryland is under a state of emergency.

This was the original report from 10:42 a.m. on Wednesday.
A winter storm watch is in effect for most of the state Wednesday, as snow moves into Maryland from the south, with "the potential for a major winter storm," according to the National Weather Service.

The winter storm watch, which means significant snow and ice accumulations may make travel difficult, is in effect from 7 p.m. Wednesday to 10 p.m. Thursday.

There is "potential for 5 or more inches of snow and sleet," according to the weather service, which said "significant accumulations of snow and sleet are likely."

Still, the exact timing and amount of accumulation are up in the air, according to officials.

"There is still some uncertainty with the exact track, timing and intensity ... which will affect snowfall amounts as well as how much sleet and rain mixes in," the weather service reported.

Winds will gust up to 35 mph, roads may be snow and sleet-covered and the snow will be heavy, the weather service reported.

Anne Arundel, Baltimore, Calvert, Carroll, Charles, Harford, Howard, Montgomery, Prince George's and St. Mary's counties are included in the winter storm watch.

Coastal flooding is possible and power outages may occur, the weather service reported.

Related: Heavy Snow in Forecast for Maryland, Outages Possible