Dew points are currently sitting in the mid teens across the Washington Area setting up a textbook Cold Air Damming (CAD) situation. As precipitation begins falling through the dry mid levels of the atmosphere, temperatures at the surface will drop into the middle 20s and hold steady through the event allowing for all precipitation to freeze on contact.
Ice accretion between a tenth and a quarter of an inch will accumulate on trees, power lines and roadways causing treacherous travel conditions. The 100 car pile up in Dallas-Ft. Worth yesterday was a result from only a tenth of an inch of ice.
Winter Storm Warnings or Ice Storm Warnings are likely along and east of Interstate 95 with a Freezing Rain Advisory likely for locations further north and west.
The image below is from the latest North American Model (NAM) showing sleet (orange) and freezing rain (pink) impacting the DC region beginning Saturday morning and wrapping up by noon on Sunday.