This appears to be Tanypus using the MND chironomid key (1), and Tanypodini to subgenus Apelopia using the keys in Roback's monograph (2). I can't place it any further using Roback's monograph: 1) his maps don't show any members of this subgenus as present anywhere near the Mid-Atlantic coast and 2) it doesn't fit well with any of the species in the key. In addition, this fly is ~25% larger than the sizes provided by Roback.

Tanypus neopunctipennis is the species that comes "closest" to the Mid-Atlantic coast but that species is supposed to have a tibial comb on the hind leg consisting of "6-8 spines". Even though Roback's text describes that comb as "rudimentary", I don't see any evidence of a comb on this individual. I also considered the possibility that this was the subgenus Tanypus species T. punctipennis but that species should have a 4 segment palpus while the present specimen appears to have only 3 segments.

I could obviously use some help here. Thanks in advance

larger image here
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comments kindly provided by Charles Watson:
"Using Roback (1971) it is clearly subgenus Apelopia. The raised, pale mesonotal tubercle and the 3-segmented maxillary palpus are clearly visible in your pictures. If you take it through his key to females, there is no evidence of a tibial comb in your detail images of Ti III. The dorsocentrals are expanded posteriorly, with 6-8 setae on each side. Regarding color, it is difficult to characterize this specimen as “brown (or dark) species” vs. “yellow species”. The dorsum of the abdomen is lighter than the venter, perhaps with dark medial markings. The vittae are dark, distinct, and contrasting with a light background. It could key to T. nubifer or T. grodhausi, depending on how you interpret the color and the number of setae in the expanded dorsocentral group.

Based on immatures, and overlap of adult characters, Roback (1971) opined that T. grodhausi could be a synonym of T. nubifer. I notice that ITIS currently follows this, treating T. grohausi as an invalid junior synonym of T. nubifer.
Tanypus (Apelopia) neopunctipennis appears to be the only species of the subgenus reported from your area (Delaware, Maryland, Pennsylvania) by Roback (1977). Tanypus nubifer has been reported as far east as Minnesota and Iowa, with T. grodhausi restricted to California (Roback 1971).

Your specimen fits the broad concept of T. nubifer, but given the range extension and the lack of recent systematic studies or comprehensive faunal surveys, I think it best to be conservative, and report this as Tanypus (A.) cf. nubifer. As used here, “cf.” is an abbreviation for a Latin term meaning “compare to” (Epler 2001).

References
Epler, J.H. 2001. Identification Manual for the larval Chironomidae (Diptera) of North and South Carolina. A guide to the taxonomy of the midges of the southeastern United States, including Florida. Special Publication SJ2001-SP13. North Carolina Department of Environment and Natural Resources, Raleigh, NC, and St. Johns River Water Management District, Palatka, FL. 526 pp.
Roback, S. S. 1971. The Subfamily Tanypodinae in North America. Monographs of the Academy of Natural Sciences of Philadelphia 17: 1 – 410.
Roback, S. S. 1977. The Immature Chironomids of the Eastern United States II. Tanypodinae – Tanypodini. Proceedings of the Academy of Natural Sciences of Philadelphia 128: 55-87."