Tex,
Like you, I'm in the DC area. I have a collection of gloves that I mix and match for layering, but do try to keep a volume of air, too, as Luis mentioned.

(1) Very thin silk-like runner's gloves (great as a liner, or beneath fingerless bike gloves when the evening chill begins)
(2) Performance Forte neoprene full finger gloves (not too tight, and they're warm to about 45 degrees or so, at least for the first hour)
(3) cotton/flannel outdoor gloves with a flippable/foldable nylon wind mitton shell that covers the fingers only (good as an outer layer with (1) or (2) or regular bike gloves beneath)
(4) windproof and thinsulate lined ski/snowboarding mittens (a great outer layer when temps plunge beneath 30 degrees). Forget dexterity, though, as it's about survival. With any combination beneath these, its warm.

I rode with (2) and (3) last night and it was toasty!

Hope this helps.
Phil