Consider yourselves warned. The National Weather Service says a “potentially crippling winter storm” is heading to the mid-Atlantic region of the U.S. Friday into early Saturday and could dump two feet of snow in Baltimore and the Washington D.C. metro area. Up to 30 inches are possible in the suburbs.

The Weather Channel said 85 million people, or one in four Americans, in 20 states were affected by weather watches, warnings or advisories on Thursday night.

“With Winter Storm Jonas organizing over the Southeast and moisture surging into cold air to the north, rain is changing over to snow on the northwest side of the system,” the network reports. “Conditions will go downhill rapidly through Saturday with blizzard conditions, heavy ice accumulations, strong winds and coastal flooding developing across the East.”

Snowfall totals through the New York City-to-Boston corridor are uncertain, but a blizzard warning is now in effect in New York City and Long Island as well as Philadelphia and parts of New Jersey and Delaware.

Flooding from the mid-Atlantic up to New England is also a threat.

In Kentucky and Illinois, the National Weather Service is calling for “significant icing.”

The D.C. area was crippled on Wednesday by just one inch of snow. The most snow the region has received in nearly a century is 20 inches.

Severe weather on Thursday as far south as Louisiana and Mississippi could precede high winds, hail, rain and even tornadoes, according to Bob Henson at the blog Weather Underground.

A state of emergency went into effect in Maryland at 7 a.m. on Friday, and state offices will close at 1 pm.

States of emergency have also been declared in Virginia, North Carolina and Pennsylvania.

A number of airlines , including Delta Air Lines Co. DAL, -3.88% and American Airlines Group Inc. AAL, -3.64% , are offering fee waivers and refunds to travelers.

Half of Friday’s flights in Charlotte have already been canceled, and other airports, including Raleigh-Durham and Reagan National, also highly affected, according to The Wall Street Journal.

For those traveling the roads, there is already talk of price hikes by D.C. cabdrivers.

Winter Storm Jonas promises to not only make a mess of things for millions of people, but could be economically costly as well. The costliest storm since 1980 was the superstorm of 1993 that resulted in more than $8 billion in losses.

Still, many won’t miss the opportunity to snap a good picture or make a good joke.