All systems are go for a significant coastal storm to affect the Mid-Atlantic region during the period of late Sunday to late Monday and snow accumulations are likely, perhaps even several inches on grassy surfaces; especially, in the N and W suburbs of DC, Philly and NYC. A strong storm, supported by a powerful upper level jet streak, is currently dumping heavy snow across the southern Rockies (e.g., 6-12 inches in Denver) and it will continue to cross the country this weekend. By later tomorrow, this “primary” low will grind to a halt over the Ohio Valley as it encounters the atmospheric roadblock that we’ve been talking about in recent days, and at this point it will transfer its energy to a developing “secondary” low near the Mid-Atlantic coastline. Precipitation will move into the Mid-Atlantic region late Sunday and come down hard for much of the day on Monday. All regions along the I-95 corridor from DC-to-Philly-to-NYC will likely see a mixed bag of precipitation at the onset of this event, but a changeover to primarily snow will occur in the N and W suburbs of these metro areas by later Sunday night or early Monday. The mixed precipitation is likely to hold on for a longer time in the immediate metro regions and to nearby locations to their south and east. Stay tuned.