A dangerous and historic snowstorm is closing in on the D.C. area. It is one we will remember for years if not generations and will likely take many days to recover from.

A blizzard warning takes effect at 3 p.m. and continues through early Sunday morning.  Light snow begins around midday and becomes heavier by the late afternoon.  Wherever you are by late afternoon, plan to be there until at least Sunday or Monday.

Overnight, the snow really starts to rip, and winds intensify.  Through Saturday, the combination of strong winds and heavy snow may produce whiteout conditions which make travel difficult to impossible.

Total snow accumulations range from about 16 to 30 inches, the highest amounts to the north and west of the District, and lowest to the southeast into Southern Maryland.

Extremely heavy snow bands that remain nearly stationary over the same areas may produce some snow totals that exceed 30 inches. We cannot pinpoint these areas ahead of time but there is a small chance (15 percent or so) that 30 inch totals could impact the immediate metro area, though we favor areas in northwest Virginia, e.g. the higher elevations near Winchester.

Near and especially southeast of the District, there remains some potential for a dry slot that would interrupt the snow  for a time Saturday and potentially result in a brief changeover from snow to sleet, cutting down accumulations.

Scattered power outages are possible due to the weight of the snow on trees and power lines as well as the wind, gusting to 30-40 mph in the metro region and over 50 mph near the Chesapeake Bay. A high wind warning has been issued for Anne Arundel, Calvert, and St. Mary’s counties late tonight through Saturday for gusts up to 65 mph.  The highest likelihood of outages may focus in these counties as not only will they have the strongest winds but also the wettest snow.

The weight of the snow may also challenge the structural integrity of some roofs in the region.

“This is a storm that is destined  to place in the top 5 in D.C. history,” says Wes Junker, Capital Weather Gang’s winter weather expert.  “The only question is where on the list we end up.”

Storm timeline for immediate metro area

11 a.m to 4 p.m. Friday: Snow moves in from southwest to northeast. Temps: 30-35. 1-2 inches accumulation.

4 p.m. to 10 p.m. Friday: Moderate snow. Temps: 25-30. Storm total accumulation: 3 to 6 inches.

10 p.m. Friday to 7 a.m. Saturday: Snow, heavy at times. Increasing winds. Temps: 25-30. Storm total accumulation: 10 to 14 inches.

7 a.m. to 5 p.m. Saturday: Snow heavy at times. Possible blizzard conditions. Brief lull, dry slot possible I-95 east. Temps: 25-30. Storm total accumulation: 14-24 inches.

5 p.m. Saturday to midnight Sunday: Snow and blowing snow, gradually decreasing. Temps: 23-28. Storm total accumulation: 16-30 inches

Why will this be such a historic storm?

Our winter weather expert, Wes Junker, explains, in brief, the science behind the storm:

“The storm’s surface low pressure center is forecast to take a perfect track from the Southeast to a position just east of Cape Hatteras and Norfolk. It then exits off the coast.”

“A very intense mid-level circulation tracks along a perfect trajectory to provide a band of heavy snow on its northwest side and that band sets up right over us though locations west of the city look to end up in the jackpot.”

“Finally, the mid-level circulation captures the surface low and causes it to stall off the coast which is the reason for the long duration of snow that we are expecting.  There is high pressure to the north so the storm so a strong pressure gradient will set up between the high and the strengthening low.  That pressure difference will be driving the winds and development of blizzard conditions.”