This looks like Japanese stilt grass which is very easy to pull up.  The ground is probably full of seed.  You could consider using a pre-emergent in late February.  http://extension.umd.edu/hgic/japanese-stiltgrass  vw

I'd like to add that the stem is strong enough and roots shallow enough that no digging is required, but you'll want to pull each stem individually.  It takes time, but is a satisfying zen experience.  Do in small segments.  Maybe have children help.  If it is a large area affected, you may want to read at nature.org about using diluted Fusion (with a surfacant added).  Regardless, be aware that there was either some on neighboring property and/or probably is now, so it will continue to come back.  But once you have cleared it, maintenance is easy.  I would walk my lawn every 2-3 weeks before mowing to pull up any new invaders.  It is so much easier if prevent patches from becoming established.
Good luck from a stiltgrass survivor in AA County