The National Weather Service expanded blizzard warnings to including New York City and Philadelphia early Friday morning. The warnings are in advance of Winter Storm Jonas, a system now developing over the southern states and expected to turn into a powerhouse winter storm by the time it reaches the East Coast later Friday and Saturday.

The blizzard warning for Philadelphia goes into effect at 7 p.m. Friday while in New York City it starts at 4 a.m. Saturday. The warnings also include areas surrounding both cities, including southeast Pennsylvania, northern Delaware, portions of New Jersey and Long Island.

Blizzard warnings also remain in effect farther south into the mid-Atlantic region, including Washington, D.C. and Baltimore.

Snowfall totals of 12 to 18 inches and sustained winds greater than 30 mph are expected across the Philadelphia region late Friday through early Sunday.

New York City is forecast to see 8 to 12 inches of snow along with wind gusts potentially over 50 mph at times on Saturday.

The combination of heavy snow and high winds will create near-zero visibility in whiteout conditions. Major highways will likely be forced to shut down during the height of the storm.

Stay with The Weather Channel and weather.com for continuing coverage of Winter Storm Jonas.