Friday Evening Jan 13 – The only main update this evening is that the Winter Weather Advisory in southern Pennsylvania has been expanded from 7 AM until midnight. This is in response the the signals that this system is behaving as I suggested earlier, and will verify a little farther north that first suggested. So once again the icing and issues will linger on the north end. Metro Baltimore will have snow or an icy mix developing in the morning, then be marginal or rise just above freezing lunch time into afternoon.
That is important in central Maryland and DC because I believe warmer air will push in farther from the south as well. So driving will not be too much of a problem mid day between Washington and Annapolis and the Eastern Shore.
Columbia and Mount Airy will be on the edge of the thaw then. The exception will be that this cold air hangs north and northeast. This includes northern Carrol, Baltimore, Harford, and Cecil Counties.
Snow should be most evident around noon between Baltimore, York, Bel Air, and Cecil County. Then gradual warming pushes north. The latest radar simulation does appear to be holding close to the arrival timeline I showed this morning. I posting that below the slider for reference.
Snow totals will be minimal as well as icing, but the typical northern counties of Maryland and southern Pennsylvania will have the concern mid day and afternoon. You will see the snow reaching Cecil County and northern Delaware, but their local NWS Office has not issued any advisories at this time.