First and foremost, this storm is another major rain event for the entire Mid-Atlantic region. Heavy rain continues throughout the region with over 1.5 inches already recorded for the day at Reagan National Airport in Washington, D.C. and enough rain in Philly to boost its year-to-date totals to over 60 inches for the first time in modern record-keeping. Heavy rain will continue right through the evening hours and thunderstorms could even mix into the picture. Later tonight, the combination of colder air moving into the upper atmosphere and colder air moving in at the surface from our northwest will change the rain to snow to around the I-95 corridor and points north and west. This rain/snow line will generally advance from the west to the east and the timetable for the changeover here in the DC metro region is between 10PM and midnight. The snow should last for a few hours in the northern and western suburbs (e.g., from Chantilly, VA to Laurel, MD) with likely accumulations of 1-3 inches and an inch or less in the District. Snow ends here at or before 5AM or so and the sun returns tomorrow, but it'll be brisk and cold.