Mostly as forecast, Sunday morning's snowfall was confined mostly to Southern Maryland, with some additional accumulations reported from the Lower Eastern Shore. BWI-Marshall Airport reported light snow from the 3 a.m. hour through the 7 a.m. hour. But forecasters at Sterling say it was melting as it landed, and will be reported as only a "trace."
The Winter Weather Advisories for Southern Maryland were lifted around 10 a.m.
Here's the National Weather Service's updated forecast map through 6 p.m. Sunday. Click to enlarge. This version makes it pretty clear where colder, drier air moving down from the north or northeast prevented enough southern moisture from getting in to produce snow.
Here is the report from the CoCoRaHS Network, still with the highly suspect 5-inch report from Waldorf. And here is more from the National Weather Service.
The NWS in Sterling notes: "In the last 50 years, from mid-March to late April, [Washington] D.C. has received 0.1 inch or more [of snow] 15 times, so [that's] a 30 percent chance. Baltimore has had that occur 26 times in the last 50 years. So [that's] about a 50 percent chance of occurrence."