We stayed in the Baltimore area last year from Feb to Aug. If you are looking for something that is open thru the winter you do not have very much of a choice. We were at Bar Harbor Resort & marina in Abingdon MD. About 20 miles north of downtown Baltimore on I-85. There are a few mobile home parks that have rv hookups also. I know of one other park open year round about 25 miles west of Baltimore off of I-70. I don't rember the name, but a search for campgrounds will bring it up. Sorry I can't give you any info any closer to Arlington.
Dan Sees, Full Timing in the MH & Part timing in a S&B In Hampstead, NC
2013 Winnebago Journey 42e, 2014 Featherlite Car Hauler 3110 17.5', 2008 Mazda MX5,
2008 Toyota FJ Cruiser